Sample records for false negative detection
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Saingam, Prakit; Li, Bo; Yan, Tao
2018-06-01
DNA-based molecular detection of microbial pathogens in complex environments is still plagued by sensitivity, specificity and robustness issues. We propose to address these issues by viewing them as inadvertent consequences of requiring specific and adequate amplification (SAA) of target DNA molecules by current PCR methods. Using the invA gene of Salmonella as the model system, we investigated if next generation sequencing (NGS) can be used to directly detect target sequences in false-negative PCR reaction (PCR-NGS) in order to remove the SAA requirement from PCR. False-negative PCR and qPCR reactions were first created using serial dilutions of laboratory-prepared Salmonella genomic DNA and then analyzed directly by NGS. Target invA sequences were detected in all false-negative PCR and qPCR reactions, which lowered the method detection limits near the theoretical minimum of single gene copy detection. The capability of the PCR-NGS approach in correcting false negativity was further tested and confirmed under more environmentally relevant conditions using Salmonella-spiked stream water and sediment samples. Finally, the PCR-NGS approach was applied to ten urban stream water samples and detected invA sequences in eight samples that would be otherwise deemed Salmonella negative. Analysis of the non-target sequences in the false-negative reactions helped to identify primer dime-like short sequences as the main cause of the false negativity. Together, the results demonstrated that the PCR-NGS approach can significantly improve method sensitivity, correct false-negative detections, and enable sequence-based analysis for failure diagnostics in complex environmental samples. Copyright © 2018 Elsevier B.V. All rights reserved.
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True detection limits in an experimental linearly heteroscedastic system.. Part 2
NASA Astrophysics Data System (ADS)
Voigtman, Edward; Abraham, Kevin T.
2011-11-01
Despite much different processing of the experimental fluorescence detection data presented in Part 1, essentially the same estimates were obtained for the true theoretical Currie decision levels ( YC and XC) and true Currie detection limits ( YD and XD). The obtained experimental values, for 5% probability of false positives and 5% probability of false negatives, were YC = 56.0 mV, YD = 125. mV, XC = 0.132 μg/mL and XD = 0.293 μg/mL. For 5% probability of false positives and 1% probability of false negatives, the obtained detection limits were YD = 158 . mV and XD = 0.371 μg/mL. Furthermore, by using bootstrapping methodology on the experimental data for the standards and the analytical blank, it was possible to validate previously published experimental domain expressions for the decision levels ( yC and xC) and detection limits ( yD and xD). This was demonstrated by testing the generated decision levels and detection limits for their performance in regard to false positives and false negatives. In every case, the obtained numbers of false negatives and false positives were as specified a priori.
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An empirical probability model of detecting species at low densities.
Delaney, David G; Leung, Brian
2010-06-01
False negatives, not detecting things that are actually present, are an important but understudied problem. False negatives are the result of our inability to perfectly detect species, especially those at low density such as endangered species or newly arriving introduced species. They reduce our ability to interpret presence-absence survey data and make sound management decisions (e.g., rapid response). To reduce the probability of false negatives, we need to compare the efficacy and sensitivity of different sampling approaches and quantify an unbiased estimate of the probability of detection. We conducted field experiments in the intertidal zone of New England and New York to test the sensitivity of two sampling approaches (quadrat vs. total area search, TAS), given different target characteristics (mobile vs. sessile). Using logistic regression we built detection curves for each sampling approach that related the sampling intensity and the density of targets to the probability of detection. The TAS approach reduced the probability of false negatives and detected targets faster than the quadrat approach. Mobility of targets increased the time to detection but did not affect detection success. Finally, we interpreted two years of presence-absence data on the distribution of the Asian shore crab (Hemigrapsus sanguineus) in New England and New York, using our probability model for false negatives. The type of experimental approach in this paper can help to reduce false negatives and increase our ability to detect species at low densities by refining sampling approaches, which can guide conservation strategies and management decisions in various areas of ecology such as conservation biology and invasion ecology.
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A statistical model of false negative and false positive detection of phase singularities.
Jacquemet, Vincent
2017-10-01
The complexity of cardiac fibrillation dynamics can be assessed by analyzing the distribution of phase singularities (PSs) observed using mapping systems. Interelectrode distance, however, limits the accuracy of PS detection. To investigate in a theoretical framework the PS false negative and false positive rates in relation to the characteristics of the mapping system and fibrillation dynamics, we propose a statistical model of phase maps with controllable number and locations of PSs. In this model, phase maps are generated from randomly distributed PSs with physiologically-plausible directions of rotation. Noise and distortion of the phase are added. PSs are detected using topological charge contour integrals on regular grids of varying resolutions. Over 100 × 10 6 realizations of the random field process are used to estimate average false negative and false positive rates using a Monte-Carlo approach. The false detection rates are shown to depend on the average distance between neighboring PSs expressed in units of interelectrode distance, following approximately a power law with exponents in the range of 1.14 to 2 for false negatives and around 2.8 for false positives. In the presence of noise or distortion of phase, false detection rates at high resolution tend to a non-zero noise-dependent lower bound. This model provides an easy-to-implement tool for benchmarking PS detection algorithms over a broad range of configurations with multiple PSs.
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True detection limits in an experimental linearly heteroscedastic system. Part 1
NASA Astrophysics Data System (ADS)
Voigtman, Edward; Abraham, Kevin T.
2011-11-01
Using a lab-constructed laser-excited filter fluorimeter deliberately designed to exhibit linearly heteroscedastic, additive Gaussian noise, it has been shown that accurate estimates may be made of the true theoretical Currie decision levels ( YC and XC) and true Currie detection limits ( YD and XD) for the detection of rhodamine 6 G tetrafluoroborate in ethanol. The obtained experimental values, for 5% probability of false positives and 5% probability of false negatives, were YC = 56.1 mV, YD = 125. mV, XC = 0.132 μg /mL and XD = 0.294 μg /mL. For 5% probability of false positives and 1% probability of false negatives, the obtained detection limits were YD = 158. mV and XD = 0.372 μg /mL. These decision levels and corresponding detection limits were shown to pass the ultimate test: they resulted in observed probabilities of false positives and false negatives that were statistically equivalent to the a priori specified values.
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Standoff detection of chemical and biological threats using laser-induced breakdown spectroscopy.
Gottfried, Jennifer L; De Lucia, Frank C; Munson, Chase A; Miziolek, Andrzej W
2008-04-01
Laser-induced breakdown spectroscopy (LIBS) is a promising technique for real-time chemical and biological warfare agent detection in the field. We have demonstrated the detection and discrimination of the biological warfare agent surrogates Bacillus subtilis (BG) (2% false negatives, 0% false positives) and ovalbumin (0% false negatives, 1% false positives) at 20 meters using standoff laser-induced breakdown spectroscopy (ST-LIBS) and linear correlation. Unknown interferent samples (not included in the model), samples on different substrates, and mixtures of BG and Arizona road dust have been classified with reasonable success using partial least squares discriminant analysis (PLS-DA). A few of the samples tested such as the soot (not included in the model) and the 25% BG:75% dust mixture resulted in a significant number of false positives or false negatives, respectively. Our preliminary results indicate that while LIBS is able to discriminate biomaterials with similar elemental compositions at standoff distances based on differences in key intensity ratios, further work is needed to reduce the number of false positives/negatives by refining the PLS-DA model to include a sufficient range of material classes and carefully selecting a detection threshold. In addition, we have demonstrated that LIBS can distinguish five different organophosphate nerve agent simulants at 20 meters, despite their similar stoichiometric formulas. Finally, a combined PLS-DA model for chemical, biological, and explosives detection using a single ST-LIBS sensor has been developed in order to demonstrate the potential of standoff LIBS for universal hazardous materials detection.
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Wu, Shan; Zhang, Xiaofeng; Shuai, Jiangbing; Li, Ke; Yu, Huizhen; Jin, Chenchen
2016-07-04
To simplify the PNA-FISH (Peptide nucleic acid-fluorescence in situ hybridization) test, molecular beacon based PNA probe combined with fluorescence scanning detection technology was applied to replace the original microscope observation to detect Listeria monocytogenes The 5′ end and 3′ end of the L. monocytogenes specific PNA probes were labeled with the fluorescent group and the quenching group respectively, to form a molecular beacon based PNA probe. When PNA probe used for fluorescence scanning and N1 treatment as the control, the false positive rate was 11.4%, and the false negative rate was 0; when N2 treatment as the control, the false positive rate decreased to 4.3%, but the false negative rate rose to 18.6%. When beacon based PNA probe used for fluorescence scanning, taken N1 treatment as blank control, the false positive rate was 8.6%, and the false negative rate was 1.4%; taken N2 treatment as blank control, the false positive rate was 5.7%, and the false negative rate was 1.4%. Compared with PNA probe, molecular beacon based PNA probe can effectively reduce false positives and false negatives. The success rates of hybridization of the two PNA probes were 83.3% and 95.2% respectively; and the rates of the two beacon based PNA probes were 91.7% and 90.5% respectively, which indicated that labeling the both ends of the PNA probe dose not decrease the hybridization rate with the target bacteria. The combination of liquid phase PNA-FISH and fluorescence scanning method, can significantly improve the detection efficiency.
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Paige F.B. Ferguson; Michael J. Conroy; Jeffrey Hepinstall-Cymerman; Nigel Yoccoz
2015-01-01
False positive detections, such as species misidentifications, occur in ecological data, although many models do not account for them. Consequently, these models are expected to generate biased inference.The main challenge in an analysis of data with false positives is to distinguish false positive and false negative...
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Sizikova, T E; Lebedev, V N; Pantyukhov, V B; Borisevich, S V; Merkulov, V A
2015-01-01
Experience of study and possible ways of elimination of false positive and false negative results during execution of polymerase chain reaction on an example of Junin virus RNA detection. MATERIALSS AND METHODS: Junin virus--causative agent of Argentine hemorrhagic fever (AHF) strain XJpR37/5787 was obtained from the State collection of pathogenicity group I causative agents of the 48th Central Research Institute. Reagent kit for detection of Junin virus RNA by RT-PCR was developed in the Institute and consists of 4 sets: for isolation of RNA, execution of reverse-transcription reaction, execution of PCR and electrophoretic detection of PCR products. RT-PCR was carried out by a standard technique. Continuous cell cultures of African green monkey Vero B, GMK-AH-1(D) were obtained from the museum of cell culture department of the Centre. An experimental study of the effect of various factors of impact on the sample under investigation ("thawing-freezing", presence of formaldehyde, heparin) on the obtaining of false negative results during Junin virus RNA detection by using RT-PCR was studied. Addition of 0.01% heparin to the samples was shown to completely inhibit PCR. Addition of 0.05% formaldehyde significantly reduces sensitivity of the method. A possibility of reduction of analysis timeframe from 15 to 5 days was shown during detection of the causative agent in samples with low concentration of the latter by growing the samples and subsequent analysis of the material obtained by using RT-PCR. During detection of causative agent by using RT-PCR false negative results could appear in the presence of formaldehyde and heparin in the sample. A possibility of elimination of false negative PCR results due to concentration of the causative agent in the sample under investigation at a level below sensitivity threshold was shown on the example of Junin virus RNA detection by using growing of the pathogen in appropriate accumulation system with subsequent analysis of the material obtained using PCR.
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Statistical approaches to account for false-positive errors in environmental DNA samples.
Lahoz-Monfort, José J; Guillera-Arroita, Gurutzeta; Tingley, Reid
2016-05-01
Environmental DNA (eDNA) sampling is prone to both false-positive and false-negative errors. We review statistical methods to account for such errors in the analysis of eDNA data and use simulations to compare the performance of different modelling approaches. Our simulations illustrate that even low false-positive rates can produce biased estimates of occupancy and detectability. We further show that removing or classifying single PCR detections in an ad hoc manner under the suspicion that such records represent false positives, as sometimes advocated in the eDNA literature, also results in biased estimation of occupancy, detectability and false-positive rates. We advocate alternative approaches to account for false-positive errors that rely on prior information, or the collection of ancillary detection data at a subset of sites using a sampling method that is not prone to false-positive errors. We illustrate the advantages of these approaches over ad hoc classifications of detections and provide practical advice and code for fitting these models in maximum likelihood and Bayesian frameworks. Given the severe bias induced by false-negative and false-positive errors, the methods presented here should be more routinely adopted in eDNA studies. © 2015 John Wiley & Sons Ltd.
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Generalized site occupancy models allowing for false positive and false negative errors
Royle, J. Andrew; Link, W.A.
2006-01-01
Site occupancy models have been developed that allow for imperfect species detection or ?false negative? observations. Such models have become widely adopted in surveys of many taxa. The most fundamental assumption underlying these models is that ?false positive? errors are not possible. That is, one cannot detect a species where it does not occur. However, such errors are possible in many sampling situations for a number of reasons, and even low false positive error rates can induce extreme bias in estimates of site occupancy when they are not accounted for. In this paper, we develop a model for site occupancy that allows for both false negative and false positive error rates. This model can be represented as a two-component finite mixture model and can be easily fitted using freely available software. We provide an analysis of avian survey data using the proposed model and present results of a brief simulation study evaluating the performance of the maximum-likelihood estimator and the naive estimator in the presence of false positive errors.
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Ferreira, Bruno G.; Falcioni, Renan; Guedes, Lubia M.; Avritzer, Sofia C.; Antunes, Werner C.; Souza, Luiz A.; Isaias, Rosy M.S.
2016-01-01
Polyethylene glycol (PEG) is a low-cost and advantageous embedding medium, which maintains the majority of cell contents unaltered during the embedding process. Some hard or complex plant materials are better embedded in PEG than in other usual embedding media. However, the histochemical tests for phenolics and lignins in PEG-embedded plant tissues commonly result in false negatives. We hypothesize that these false negatives should be prevented by the use of distinct fixatives, which should avoid the bonds between PEG and phenols. Novel protocols for phenolics and flavanols detection are efficiently tested, with fixation of the samples in ferrous sulfate and formalin or in caffeine and sodium benzoate, respectively. The differentiation of lignin types is possible in safranin-stained sections observed under fluorescence. The Maule’s test faultlessly distinguishes syringyl-rich from guaiacyl- and hydroxyphenyl-rich lignins in PEG-embedded material under light microscopy. Current hypothesis is corroborated, that is, the adequate fixation solves the false-negative results, and the new proposed protocols fill up some gaps on the detection of phenolics and lignins. PMID:28117630
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Rahal, M; Kervaire, B; Villard, J; Tiercy, J-M
2008-03-01
Human leukocyte antigen (HLA) typing by polymerase chain reaction-sequence-specific oligonucleotide (PCR-SSO) hybridization on solid phase (microbead assay) or polymerase chain reaction-sequence-specific primers (PCR-SSP) requires interpretation softwares to detect all possible allele combinations. These programs propose allele calls by taking into account false-positive or false-negative signal(s). The laboratory has the option to validate typing results in the presence of strongly cross-reacting or apparent false-negative signals. Alternatively, these seemingly aberrant signals may disclose novel variants. We report here four new HLA-B (B*5620 and B*5716) and HLA-DRB1 alleles (DRB1*110107 and DRB1*1474) that were detected by apparent false-negative or -positive hybridization or amplification patterns, and ultimately resolved by sequencing. To avoid allele misassignments, a comprehensive evaluation of acquired data as documented in a quality assurance system is therefore required to confirm unambiguous typing interpretation.
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Estimated number of infants detected and missed by critical congenital heart defect screening.
Ailes, Elizabeth C; Gilboa, Suzanne M; Honein, Margaret A; Oster, Matthew E
2015-06-01
In 2011, the US Secretary of Health and Human Services recommended universal screening of newborns for critical congenital heart defects (CCHDs), yet few estimates of the number of infants with CCHDs likely to be detected through universal screening exist. Our objective was to estimate the number of infants with nonsyndromic CCHDs in the United States likely to be detected (true positives) and missed (false negatives) through universal newborn CCHD screening. We developed a simulation model based on estimates of birth prevalence, prenatal diagnosis, late detection, and sensitivity of newborn CCHD screening through pulse oximetry to estimate the number of true-positive and false-negative nonsyndromic cases of the 7 primary and 5 secondary CCHD screening targets identified through screening. We estimated that 875 (95% uncertainty interval [UI]: 705-1060) US infants with nonsyndromic CCHDs, including 470 (95% UI: 360-585) infants with primary CCHD screening targets, will be detected annually through newborn CCHD screening. An additional 880 (UI: 700-1080) false-negative screenings, including 280 (95% UI: 195-385) among primary screening targets, are expected. We estimated that similar numbers of CCHDs would be detected under scenarios comparing "lower" (∼19%) and "higher" (∼41%) than current prenatal detection prevalences. A substantial number of nonsyndromic CCHD cases are likely to be detected through universal CCHD screening; however, an equal number of false-negative screenings, primarily among secondary targets of screening, are likely to occur. Future efforts should document the true impact of CCHD screening in practice. Copyright © 2015 by the American Academy of Pediatrics.
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Trinh, Tony W; Glazer, Daniel I; Sadow, Cheryl A; Sahni, V Anik; Geller, Nina L; Silverman, Stuart G
2018-03-01
To determine test characteristics of CT urography for detecting bladder cancer in patients with hematuria and those undergoing surveillance, and to analyze reasons for false-positive and false-negative results. A HIPAA-compliant, IRB-approved retrospective review of reports from 1623 CT urograms between 10/2010 and 12/31/2013 was performed. 710 examinations for hematuria or bladder cancer history were compared to cystoscopy performed within 6 months. Reference standard was surgical pathology or 1-year minimum clinical follow-up. False-positive and false-negative examinations were reviewed to determine reasons for errors. Ninety-five bladder cancers were detected. CT urography accuracy: was 91.5% (650/710), sensitivity 86.3% (82/95), specificity 92.4% (568/615), positive predictive value 63.6% (82/129), and negative predictive value was 97.8% (568/581). Of 43 false positives, the majority of interpretation errors were due to benign prostatic hyperplasia (n = 12), trabeculated bladder (n = 9), and treatment changes (n = 8). Other causes include blood clots, mistaken normal anatomy, infectious/inflammatory changes, or had no cystoscopic correlate. Of 13 false negatives, 11 were due to technique, one to a large urinary residual, one to artifact. There were no errors in perception. CT urography is an accurate test for diagnosing bladder cancer; however, in protocols relying predominantly on excretory phase images, overall sensitivity remains insufficient to obviate cystoscopy. Awareness of bladder cancer mimics may reduce false-positive results. Improvements in CTU technique may reduce false-negative results.
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Griffey, Richard T; Trent, Caleb J; Bavolek, Rebecca A; Keeperman, Jacob B; Sampson, Christopher; Poirier, Robert F
2013-01-01
Failure to detect pregnancy in the emergency department (ED) can have important consequences. Urine human chorionic gonadotropin (uhCG) point-of-care (POC) assays are valued for rapidly detecting early pregnancy with high sensitivity. However, under certain conditions, POC uhCG tests can fail to detect pregnancy. In investigating a series of late first-trimester false-negative pregnancy tests in our ED, a novel and distinct causative phenomenon was recently elucidated in our institution. We discuss uhCG POC tests, review our false-negative rate, and describe mechanisms for false negatives and potential remedies. The false-negative POC uhCG rate is very low, but in the setting of a large volume of tests, the numbers are worth consideration. In positive uhCG POC tests, free and fixed antibodies bind hCG to form a "sandwich"; hCG is present in several variant forms that change in their concentrations at different stages of pregnancy. When in excess, intact hCG can saturate the antibodies, preventing sandwich formation (hook effect phenomenon). Some assays may include an antibody that does not recognize certain variants present in later stages of pregnancy. When this variant is in excess, it can bind one antibody avidly and the other not at all, resulting in a false-negative test (hook-like phenomenon). In both situations, dilution is key to an accurate test. Manufacturers should consider that uhCG tests are routinely used at many stages of pregnancy. Characterizing uhCG variants recognized by their tests and eliminating lot-to-lot variability may help improve uhCG test performance. Clinicians need to be aware of and familiarize themselves with the limitations of the specific type of uhCG POC tests used in their practice, recognizing that under certain circumstances, false-negative tests can occur. Copyright © 2013 Elsevier Inc. All rights reserved.
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Matsuda, Chikashi; Moriyama, Hidehiko; Taketani, Takeshi; Shibata, Hiroshi; Nagai, Atsushi
2011-01-01
The presence in serum of the Hepatitis B surface antigen (HBsAg), the outer envelope of the hepatitis B virus (HBV), indicates viral infection, used in laboratory tests to confirm this. We report a case of discrepancy among HBsAg test results detected between measurements in a subject with HB infection. Gene analysis demonstrated several S region gene mutations, not detected previously. We tested 12 measurements e.g., EIA, CLIA, CLEIA, F-EIA, MAT, and IC for whether they could detect our subject's HBsAg and found that it was not recognized by a method using only a single monoclonal antibody to detect HBsAg in two detection processes, in contrast to the 11 other measurements, which used two different antibodies. This case shows that amino acid substitution may cause a false negative result for HBsAg. Gene mutations known to occur in HBV, should thus trigger an awareness of the need to keep in mind that false negative results can happen in case such as ours.
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Use of General-purpose Negation Detection to Augment Concept Indexing of Medical Documents
Mutalik, Pradeep G.; Deshpande, Aniruddha; Nadkarni, Prakash M.
2001-01-01
Objectives: To test the hypothesis that most instances of negated concepts in dictated medical documents can be detected by a strategy that relies on tools developed for the parsing of formal (computer) languages—specifically, a lexical scanner (“lexer”) that uses regular expressions to generate a finite state machine, and a parser that relies on a restricted subset of context-free grammars, known as LALR(1) grammars. Methods: A diverse training set of 40 medical documents from a variety of specialties was manually inspected and used to develop a program (Negfinder) that contained rules to recognize a large set of negated patterns occurring in the text. Negfinder's lexer and parser were developed using tools normally used to generate programming language compilers. The input to Negfinder consisted of medical narrative that was preprocessed to recognize UMLS concepts: the text of a recognized concept had been replaced with a coded representation that included its UMLS concept ID. The program generated an index with one entry per instance of a concept in the document, where the presence or absence of negation of that concept was recorded. This information was used to mark up the text of each document by color-coding it to make it easier to inspect. The parser was then evaluated in two ways: 1) a test set of 60 documents (30 discharge summaries, 30 surgical notes) marked-up by Negfinder was inspected visually to quantify false-positive and false-negative results; and 2) a different test set of 10 documents was independently examined for negatives by a human observer and by Negfinder, and the results were compared. Results: In the first evaluation using marked-up documents, 8,358 instances of UMLS concepts were detected in the 60 documents, of which 544 were negations detected by the program and verified by human observation (true-positive results, or TPs). Thirteen instances were wrongly flagged as negated (false-positive results, or FPs), and the program missed 27 instances of negation (false-negative results, or FNs), yielding a sensitivity of 95.3 percent and a specificity of 97.7 percent. In the second evaluation using independent negation detection, 1,869 concepts were detected in 10 documents, with 135 TPs, 12 FPs, and 6 FNs, yielding a sensitivity of 95.7 percent and a specificity of 91.8 percent. One of the words “no,” “denies/denied,” “not,” or “without” was present in 92.5 percent of all negations. Conclusions: Negation of most concepts in medical narrative can be reliably detected by a simple strategy. The reliability of detection depends on several factors, the most important being the accuracy of concept matching. PMID:11687566
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Hofvind, Solveig; Sagstad, Silje; Sebuødegård, Sofie; Chen, Ying; Roman, Marta; Lee, Christoph I
2018-04-01
Purpose To compare rates and tumor characteristics of interval breast cancers (IBCs) detected after a negative versus false-positive screening among women participating in the Norwegian Breast Cancer Screening Program. Materials and Methods The Cancer Registry Regulation approved this retrospective study. Information about 423 445 women aged 49-71 years who underwent 789 481 full-field digital mammographic screening examinations during 2004-2012 was extracted from the Cancer Registry of Norway. Rates and odds ratios of IBC among women with a negative (the reference group) versus a false-positive screening were estimated by using logistic regression models adjusted for age at diagnosis and county of residence. Results A total of 1302 IBCs were diagnosed after 789 481 screening examinations, of which 7.0% (91 of 1302) were detected among women with a false-positive screening as the most recent breast imaging examination before detection. By using negative screening as the reference, adjusted odds ratios of IBCs were 3.3 (95% confidence interval [CI]: 2.6, 4.2) and 2.8 (95% CI: 1.8, 4.4) for women with a false-positive screening without and with needle biopsy, respectively. Women with a previous negative screening had a significantly lower proportion of tumors that were 10 mm or less (14.3% [150 of 1049] vs 50.0% [seven of 14], respectively; P < .01) and grade I tumors (13.2% [147 of 1114] vs 42.9% [six of 14]; P < .01), but a higher proportion of cases with lymph nodes positive for cancer (40.9% [442 of 1080] vs 13.3% [two of 15], respectively; P = .03) compared with women with a previous false-positive screening with benign biopsy. A retrospective review of the screening mammographic examinations identified 42.9% (39 of 91) of the false-positive cases to be the same lesion as the IBC. Conclusion By using a negative screening as the reference, a false-positive screening examination increased the risk of an IBC three-fold. The tumor characteristics of IBC after a negative screening were less favorable compared with those detected after a previous false-positive screening. © RSNA, 2017 Online supplemental material is available for this article.
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Risk management and precaution: insights on the cautious use of evidence.
Hrudey, Steve E; Leiss, William
2003-01-01
Risk management, done well, should be inherently precautionary. Adopting an appropriate degree of precaution with respect to feared health and environmental hazards is fundamental to risk management. The real problem is in deciding how precautionary to be in the face of inevitable uncertainties, demanding that we understand the equally inevitable false positives and false negatives from screening evidence. We consider a framework for detection and judgment of evidence of well-characterized hazards, using the concepts of sensitivity, specificity, positive predictive value, and negative predictive value that are well established for medical diagnosis. Our confidence in predicting the likelihood of a true danger inevitably will be poor for rare hazards because of the predominance of false positives; failing to detect a true danger is less likely because false negatives must be rarer than the danger itself. Because most controversial environmental hazards arise infrequently, this truth poses a dilemma for risk management. PMID:14527835
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Miller, James Christopher; Rennie, John Alan; Toevs, James Waldo
The introduction points out that radiation backgrounds fluctuate across very short distances: factors include geology, soil composition, altitude, building structures, topography, and other manmade structures; and asphalt and concrete can vary significantly over short distances. Brief descriptions are given of the detection system, experimental setup, and background variation measurements. It is concluded that positive and negative gradients can greatly reduce the detection sensitivity of an MDS: negative gradients create opportunities for false negatives (nondetection), and positive gradients create a potentially unacceptable FAR (above 1%); the location of use for mobile detection is important to understand; spectroscopic systems provide more informationmore » for screening out false alarms and may be preferred for mobile use; and mobile monitor testing at LANL accounts for expected variations in the background.« less
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Lao, Annabelle Y; Sharma, Vijay K; Tsivgoulis, Georgios; Frey, James L; Malkoff, Marc D; Navarro, Jose C; Alexandrov, Andrei V
2008-10-01
International Consensus Criteria (ICC) consider right-to-left shunt (RLS) present when Transcranial Doppler (TCD) detects even one microbubble (microB). Spencer Logarithmic Scale (SLS) offers more grades of RLS with detection of >30 microB corresponding to a large shunt. We compared the yield of ICC and SLS in detection and quantification of a large RLS. We prospectively evaluated paradoxical embolism in consecutive patients with ischemic strokes or transient ischemic attack (TIA) using injections of 9 cc saline agitated with 1 cc of air. Results were classified according to ICC [negative (no microB), grade I (1-20 microB), grade II (>20 microB or "shower" appearance of microB), and grade III ("curtain" appearance of microB)] and SLS criteria [negative (no microB), grade I (1-10 microB), grade II (11-30 microB), grade III (31100 microB), grade IV (101300 microB), grade V (>300 microB)]. The RLS size was defined as large (>4 mm) using diameter measurement of the septal defects on transesophageal echocardiography (TEE). TCD comparison to TEE showed 24 true positive, 48 true negative, 4 false positive, and 2 false negative cases (sensitivity 92.3%, specificity 92.3%, positive predictive value (PPV) 85.7%, negative predictive value (NPV) 96%, and accuracy 92.3%) for any RLS presence. Both ICC and SLS were 100% sensitive for detection of large RLS. ICC and SLS criteria yielded a false positive rate of 24.4% and 7.7%, respectively when compared to TEE. Although both grading scales provide agreement as to any shunt presence, using the Spencer Scale grade III or higher can decrease by one-half the number of false positive TCD diagnoses to predict large RLS on TEE.
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Clinical significance of FDG-PET/CT at the postoperative surveillance in the breast cancer patients.
Jung, Na Young; Yoo, Ie Ryung; Kang, Bong Joo; Kim, Sung Hun; Chae, Byung Joo; Seo, Ye Young
2016-01-01
We evaluated the clinical role of [(18)F]-2-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG-PET/CT) compared with conventional imaging (CI) to detect locoregional recurrence or distant metastasis during postoperative surveillance of patients with breast cancer. We included 1,819 examinations of 1,161 patients, who underwent FDG-PET/CT and CI, including mammography, breast ultrasound, whole-body bone scintigraphy, and chest radiography for postoperative surveillance. All patients had a history of surgery with or without adjuvant treatment due to more than stage II breast cancer between November 2003 and November 2009. We evaluated the diagnostic performance of CI, FDG-PET/CT, and combined CI and FDG-PET/CT for detecting locoregional recurrence, distant metastasis, and incidental cancer. We also analyzed false-positive and false-negative results in both FDG-PET/CT and CI. Sensitivity, specificity, positive predictive value, and negative predictive value of CI were 75.4, 98.7, 93.4, and 94.3 %. Those of FDG-PET/CT were 97.5, 98.8, 95.4, and 99.4 %. Those of the combined results were 98.6, 98.2, 96.7, and 99.7 %. Sensitivity of FDG-PET/CT was significantly higher than that of CI (P < 0.05). Sensitivity of combined CI and FDG-PET/CT results improved, but they were not significantly different from those of FDG-PET/CT alone (P = 0.43). Seventeen false-positive and nine false-negative cases were detected with FDG-PET/CT, and 19 false-positive and 88 false-negative cases were detected with CI. FDG-PET/CT is considered as an acceptable diagnostic imaging modality for postoperative surveillance of patients with breast cancer.
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van der Meulen, Miriam P; Lansdorp-Vogelaar, Iris; van Heijningen, Else-Mariëtte B; Kuipers, Ernst J; van Ballegooijen, Marjolein
2016-06-01
If some adenomas do not bleed over several years, they will cause systematic false-negative fecal immunochemical test (FIT) results. The long-term effectiveness of FIT screening has been estimated without accounting for such systematic false-negativity. There are now data with which to evaluate this issue. The authors developed one microsimulation model (MISCAN [MIcrosimulation SCreening ANalysis]-Colon) without systematic false-negative FIT results and one model that allowed a percentage of adenomas to be systematically missed in successive FIT screening rounds. Both variants were adjusted to reproduce the first-round findings of the Dutch CORERO FIT screening trial. The authors then compared simulated detection rates in the second screening round with those observed, and adjusted the simulated percentage of systematically missed adenomas to those data. Finally, the authors calculated the impact of systematic false-negative FIT results on the effectiveness of repeated FIT screening. The model without systematic false-negativity simulated higher detection rates in the second screening round than observed. These observed rates could be reproduced when assuming that FIT systematically missed 26% of advanced and 73% of nonadvanced adenomas. To reduce the false-positive rate in the second round to the observed level, the authors also had to assume that 30% of false-positive findings were systematically false-positive. Systematic false-negative FIT testing limits the long-term reduction of biennial FIT screening in the incidence of colorectal cancer (35.6% vs 40.9%) and its mortality (55.2% vs 59.0%) in participants. The results of the current study provide convincing evidence based on the combination of real-life and modeling data that a percentage of adenomas are systematically missed by repeat FIT screening. This impairs the efficacy of FIT screening. Cancer 2016;122:1680-8. © 2016 American Cancer Society. © 2016 American Cancer Society.
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McClintock, Brett T.; Bailey, Larissa L.; Pollock, Kenneth H.; Simons, Theodore R.
2010-01-01
The recent surge in the development and application of species occurrence models has been associated with an acknowledgment among ecologists that species are detected imperfectly due to observation error. Standard models now allow unbiased estimation of occupancy probability when false negative detections occur, but this is conditional on no false positive detections and sufficient incorporation of explanatory variables for the false negative detection process. These assumptions are likely reasonable in many circumstances, but there is mounting evidence that false positive errors and detection probability heterogeneity may be much more prevalent in studies relying on auditory cues for species detection (e.g., songbird or calling amphibian surveys). We used field survey data from a simulated calling anuran system of known occupancy state to investigate the biases induced by these errors in dynamic models of species occurrence. Despite the participation of expert observers in simplified field conditions, both false positive errors and site detection probability heterogeneity were extensive for most species in the survey. We found that even low levels of false positive errors, constituting as little as 1% of all detections, can cause severe overestimation of site occupancy, colonization, and local extinction probabilities. Further, unmodeled detection probability heterogeneity induced substantial underestimation of occupancy and overestimation of colonization and local extinction probabilities. Completely spurious relationships between species occurrence and explanatory variables were also found. Such misleading inferences would likely have deleterious implications for conservation and management programs. We contend that all forms of observation error, including false positive errors and heterogeneous detection probabilities, must be incorporated into the estimation framework to facilitate reliable inferences about occupancy and its associated vital rate parameters.
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Sentinel Lymph Node Detection Using Carbon Nanoparticles in Patients with Early Breast Cancer
Lu, Jianping; Zeng, Yi; Chen, Xia; Yan, Jun
2015-01-01
Purpose Carbon nanoparticles have a strong affinity for the lymphatic system. The purpose of this study was to evaluate the feasibility of sentinel lymph node biopsy using carbon nanoparticles in early breast cancer and to optimize the application procedure. Methods Firstly, we performed a pilot study to demonstrate the optimized condition using carbon nanoparticles for sentinel lymph nodes (SLNs) detection by investigating 36 clinically node negative breast cancer patients. In subsequent prospective study, 83 patients with clinically node negative breast cancer were included to evaluate SLNs using carbon nanoparticles. Another 83 SLNs were detected by using blue dye. SLNs detection parameters were compared between the methods. All patients irrespective of the SLNs status underwent axillary lymph node dissection for verification of axillary node status after the SLN biopsy. Results In pilot study, a 1 ml carbon nanoparticles suspension used 10–15min before surgery was associated with the best detection rate. In subsequent prospective study, with carbon nanoparticles, the identification rate, accuracy, false negative rate was 100%, 96.4%, 11.1%, respectively. The identification rate and accuracy were 88% and 95.5% with 15.8% of false negative rate using blue dye technique. The use of carbon nanoparticles suspension showed significantly superior results in identification rate (p = 0.001) and reduced false-negative results compared with blue dye technique. Conclusion Our study demonstrated feasibility and accuracy of using carbon nanoparticles for SLNs mapping in breast cancer patients. Carbon nanoparticles are useful in SLNs detection in institutions without access to radioisotope. PMID:26296136
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Singh, Gurmukh
2017-01-01
Background Serum free light chain assay (SFLCA) and κ/λ ratio, and protein electrophoretic methods are used in the diagnosis and monitoring of monoclonal gammopathies. Methods Results for serum free light chains, serum and urine protein electrophoreses and immunofixation electrophoreses in 468 patients with a diagnosis of monoclonal gammopathy were compared. The results of the two methods were graded as concordant, non-concordant or discordant with the established diagnoses to assess the relative performance of the methods. Results of κ/λ ratio in samples with monoclonal protein detectable by electrophoretic methods were also analyzed. Results Protein electrophoreses results were concordant with the established diagnoses significantly more often than κ/λ ratio. The false negative rate for κ/λ ratio was higher than that for electrophoretic methods. κ/λ ratio was falsely negative in about 27% of the 1,860 samples with detectable monoclonal immunoglobulin. The false negative rate was higher in lesions with lambda chains (32%) than those with kappa chains (24%). The false negative rate for κ/λ ratio was over 55% in samples with monoclonal gammopathy of undetermined significance. Even at first encounter, the false negative rates for κ/λ ratios for monoclonal gammopathy of undetermined significance, smoldering myeloma and multiple myeloma were 66.98%, 23.08%, and 30.15%, respectively, with false negative rate for lambda chain lesions being higher. Conclusions Electrophoretic studies of serum and urine are superior to SFLCA and κ/λ ratio. Abnormal κ/λ ratio, per se, is not diagnostic of monoclonal gammopathy. A normal κ/λ ratio does not exclude monoclonal gammopathy. False negative rates for lesions with lambda chain are higher than those for lesions with kappa chains. Electrophoretic studies of urine are underutilized. Clinical usefulness and medical necessity of SFLCA and κ/λ ratio is of questionable value in routine clinical testing. PMID:27924175
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Singh, Gurmukh
2017-01-01
Serum free light chain assay (SFLCA) and κ/λ ratio, and protein electrophoretic methods are used in the diagnosis and monitoring of monoclonal gammopathies. Results for serum free light chains, serum and urine protein electrophoreses and immunofixation electrophoreses in 468 patients with a diagnosis of monoclonal gammopathy were compared. The results of the two methods were graded as concordant, non-concordant or discordant with the established diagnoses to assess the relative performance of the methods. Results of κ/λ ratio in samples with monoclonal protein detectable by electrophoretic methods were also analyzed. Protein electrophoreses results were concordant with the established diagnoses significantly more often than κ/λ ratio. The false negative rate for κ/λ ratio was higher than that for electrophoretic methods. κ/λ ratio was falsely negative in about 27% of the 1,860 samples with detectable monoclonal immunoglobulin. The false negative rate was higher in lesions with lambda chains (32%) than those with kappa chains (24%). The false negative rate for κ/λ ratio was over 55% in samples with monoclonal gammopathy of undetermined significance. Even at first encounter, the false negative rates for κ/λ ratios for monoclonal gammopathy of undetermined significance, smoldering myeloma and multiple myeloma were 66.98%, 23.08%, and 30.15%, respectively, with false negative rate for lambda chain lesions being higher. Electrophoretic studies of serum and urine are superior to SFLCA and κ/λ ratio. Abnormal κ/λ ratio, per se , is not diagnostic of monoclonal gammopathy. A normal κ/λ ratio does not exclude monoclonal gammopathy. False negative rates for lesions with lambda chain are higher than those for lesions with kappa chains. Electrophoretic studies of urine are underutilized. Clinical usefulness and medical necessity of SFLCA and κ/λ ratio is of questionable value in routine clinical testing.
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Can missed breast cancer be recognized by regular peer auditing on screening mammography?
Pan, Huay-Ben; Yang, Tsung-Lung; Hsu, Giu-Cheng; Chiang, Chia-Ling; Huang, Jer-Shyung; Chou, Chen-Pin; Wang, Yen-Chi; Liang, Huei-Lung; Lee, San-Kan; Chou, Yi-Hong; Wong, Kam-Fai
2012-09-01
This study was conducted to investigate whether detectable missed breast cancers could be distinguished from truly false negative images in a mammographic screening by a regular peer auditing. Between 2004 and 2007, a total of 311,193 free nationwide biennial mammographic screenings were performed for 50- to 69-year-old women in Taiwan. Retrospectively comparing the records in Taiwan's Cancer registry, 1283 cancers were detected (4.1 per 1000). Of the total, 176 (0.6 per 1000) initial mammographic negative assessments were reported to have cancers (128 traditional films and 48 laser-printed digital images). We selected 186 true negative films (138 traditional films and 48 laser-printed ones) as control group. These were seeded into 4815 films of 2008 images to be audited in 2009. Thirty-four auditors interpreted all the films in a single-blind, randomized, pair-control study. The performance of 34 auditors was analyzed by chi-square test. A p value of < 0.05 was considered significant. Eight (6 traditional and 2 digital films) of the 176 false negative films were not reported by the auditors (missing rate of 4.5%). Of this total, 87 false negatives were reassessed as positive, while 29 of the 186 true negatives were reassessed as positive, making the overall performance of the 34 auditors in interpreting the false negatives and true negatives a specificity of 84.4% and sensitivity of 51.8%. The specificity and sensitivity in traditional films and laser-printed films were 98.6% versus 43.8% and 41.8% versus 78.3%, respectively. Almost 42% of the traditional false negative films had positive reassessment by the auditors, showing a significant difference from the initial screeners (p < 0.001). The specificity of their reinterpretation of laser-printed films was obviously low. Almost 42% of the false negative traditional films were judged as missed cancers in this study. A peer auditing should reduce the probability of missed cancers. 2012 Published by Elsevier B.V
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Applying a CAD-generated imaging marker to assess short-term breast cancer risk
NASA Astrophysics Data System (ADS)
Mirniaharikandehei, Seyedehnafiseh; Zarafshani, Ali; Heidari, Morteza; Wang, Yunzhi; Aghaei, Faranak; Zheng, Bin
2018-02-01
Although whether using computer-aided detection (CAD) helps improve radiologists' performance in reading and interpreting mammograms is controversy due to higher false-positive detection rates, objective of this study is to investigate and test a new hypothesis that CAD-generated false-positives, in particular, the bilateral summation of false-positives, is a potential imaging marker associated with short-term breast cancer risk. An image dataset involving negative screening mammograms acquired from 1,044 women was retrospectively assembled. Each case involves 4 images of craniocaudal (CC) and mediolateral oblique (MLO) view of the left and right breasts. In the next subsequent mammography screening, 402 cases were positive for cancer detected and 642 remained negative. A CAD scheme was applied to process all "prior" negative mammograms. Some features from CAD scheme were extracted, which include detection seeds, the total number of false-positive regions, an average of detection scores and the sum of detection scores in CC and MLO view images. Then the features computed from two bilateral images of left and right breasts from either CC or MLO view were combined. In order to predict the likelihood of each testing case being positive in the next subsequent screening, two logistic regression models were trained and tested using a leave-one-case-out based cross-validation method. Data analysis demonstrated the maximum prediction accuracy with an area under a ROC curve of AUC=0.65+/-0.017 and the maximum adjusted odds ratio of 4.49 with a 95% confidence interval of [2.95, 6.83]. The results also illustrated an increasing trend in the adjusted odds ratio and risk prediction scores (p<0.01). Thus, the study showed that CAD-generated false-positives might provide a new quantitative imaging marker to help assess short-term breast cancer risk.
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Goldenberg, S D; Cliff, P R; Smith, S; Milner, M; French, G L
2010-01-01
Current diagnosis of Clostridium difficile infection (CDI) relies upon detection of toxins A/B in stool by enzyme immunoassay [EIA(A/B)]. This strategy is unsatisfactory because it has a low sensitivity resulting in significant false negatives. We investigated the performance of a two-step algorithm for diagnosis of CDI using detection of glutamate dehydrogenase (GDH). GDH-positive samples were tested for C. difficile toxin B gene (tcdB) by polymerase chain reaction (PCR). The performance of the two-step protocol was compared with toxin detection by the Meridian Premier EIA kit in 500 consecutive stool samples from patients with suspected CDI. The reference standard among samples that were positive by either EIA(A/B) or GDH testing was culture cytotoxin neutralisation (culture/CTN). Thirty-six (7%) of 500 samples were identified as true positives by culture/CTN. EIA(A/B) identified 14 of the positive specimens with 22 false negatives and two false positives. The two-step protocol identified 34 of the positive samples with two false positives and two false negatives. EIA(A/B) had a sensitivity of 39%, specificity of 99%, positive predictive value of 88% and negative predictive value of 95%. The two-step algorithm performed better, with corresponding values of 94%, 99%, 94% and 99% respectively. Screening for GDH before confirmation of positives by PCR is cheaper than screening all specimens by PCR and is an effective method for routine use. Current EIA(A/B) tests for CDI are of inadequate sensitivity and should be replaced; however, this may result in apparent changes in CDI rates that would need to be explained in national surveillance statistics. Copyright 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.
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A novel approach to describing and detecting performance anti-patterns
NASA Astrophysics Data System (ADS)
Sheng, Jinfang; Wang, Yihan; Hu, Peipei; Wang, Bin
2017-08-01
Anti-pattern, as an extension to pattern, describes a widely used poor solution which can bring negative influence to application systems. Aiming at the shortcomings of the existing anti-pattern descriptions, an anti-pattern description method based on first order predicate is proposed. This method synthesizes anti-pattern forms and symptoms, which makes the description more accurate and has good scalability and versatility as well. In order to improve the accuracy of anti-pattern detection, a Bayesian classification method is applied in validation for detection results, which can reduce false negatives and false positives of anti-pattern detection. Finally, the proposed approach in this paper is applied to a small e-commerce system, the feasibility and effectiveness of the approach is demonstrated further through experiments.
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Reducing false negatives in clinical practice: the role of neural network technology.
Mango, L J
1996-10-01
The fact that some cervical smears result in false-negative findings is an unavoidable and unpredictable consequence of the conventional (manual microscopic) method of screening. Errors in the detection and interpretation of abnormality are cited as leading causes of false-negative cytology findings; these are random errors that are not known to correlate with any patient risk factor, which makes the false-negative findings a "silent" threat that is difficult to prevent. Described by many as a labor-intensive procedure, the microscopic evaluation of a cervical smear involves a detailed search among hundreds of thousands of cells on each smear for a possible few that may indicate abnormality. Investigations into causes of false-negative findings preceding the discovery of high-grade lesions found that many smears had very few diagnostic cells that were often very small in size. These small cells were initially overlooked or misinterpreted and repeatedly missed on rescreening. PAPNET testing is designed to supplement conventional screening by detecting abnormal cells that initially may have been missed by microscopic examination. This interactive system uses neural networks, a type of artificial intelligence well suited for pattern recognition, to automate the arduous search for abnormality. The instrument focuses the review of suspicious cells by a trained cytologist. Clinical studies indicate that PAPNET testing is sensitive to abnormality typically missed by conventional screening and that its use as a supplemental test improves the accuracy of screening.
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USDA-ARS?s Scientific Manuscript database
Plant pathogen detection systems have been useful tools to monitor inoculum presence and initiate management schedules. More recently, a LAMP assay was successfully designed for field use in the grape powdery mildew pathosystem; however, false negatives or false positives were prevalent in grower-co...
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The value of a transformation zone component in anal cytology to detect HSIL.
Roberts, Jennifer M; Jin, Fengyi; Thurloe, Julia K; Ekman, Deborah; Adams, Marjorie K; McDonald, Ross L; Biro, Clare; Poynten, I Mary; Grulich, Andrew E; Farnsworth, Annabelle
2016-08-01
In a cytology-based screening program intended to prevent anal cancer, the anal transformation zone (TZ) should be adequately sampled because it is the site most susceptible to the development of the cancer precursor, high-grade squamous intraepithelial lesion (HSIL). An adequate TZ component is defined as comprising at least 10 rectal columnar or squamous metaplastic cells. In the current study, the authors examined whether the presence of a TZ component in anal cytology correlated with the detection of histological HSIL. In a natural history study of anal human papillomavirus infection in homosexual men, all participants underwent liquid-based cytology and high-resolution anoscopy (HRA) with or without biopsy at each visit. True-negative cytology (negative cytology with non-HSIL biopsy or negative HRA), false-negative cytology (negative cytology with HSIL biopsy), and true-positive cytology (abnormal cytology with HSIL biopsy) were compared with regard to the presence or absence of a TZ component. Of 617 participants, baseline results included 155 true-positive results, 191 true-negative results, and 31 false-negative results. The absence of an adequate TZ component was found to be significantly higher for false-negative (32.3%) than for either true-positive (11.0%; P = .0034) or true-negative (13.1%; P = .0089) results. Significantly more false-negative cases lacked a TZ component compared with either true-positive or true-negative cases. TZ cells may be an important indicator of sample quality for anal cytology because, unlike cervical sampling, the anal canal is not visualized during cytology sampling. Cancer Cytopathol 2016;124:596-601. © 2016 American Cancer Society. © 2016 American Cancer Society.
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Raza, Shaan M; Banu, Matei A; Donaldson, Angela; Patel, Kunal S; Anand, Vijay K; Schwartz, Theodore H
2016-03-01
The intraoperative detection of CSF leaks during endonasal endoscopic skull base surgery is critical to preventing postoperative CSF leaks. Intrathecal fluorescein (ITF) has been used at varying doses to aid in the detection of intraoperative CSF leaks. However, the sensitivity and specificity of ITF at certain dosages is unknown. A prospective database of all endoscopic endonasal procedures was reviewed. All patients received 25 mg ITF diluted in 10 ml CSF and were pretreated with dexamethasone and Benadryl. Immediately after surgery, the operating surgeon prospectively noted if there was an intraoperative CSF leak and fluorescein was identified. The sensitivity, specificity, and positive and negative predictive power of ITF for detecting intraoperative CSF leak were calculated. Factors correlating with postoperative CSF leak were determined. Of 419 patients, 35.8% of patients did not show a CSF leak. Fluorescein-tinted CSF (true positive) was noted in 59.7% of patients and 0 false positives were encountered. CSF without fluorescein staining (false negative) was noted in 4.5% of patients. The sensitivity and specificity of ITF were 92.9% and 100%, respectively. The negative and positive predictive values were 88.8% and 100%, respectively. Postoperative CSF leaks only occurred in true positives at a rate of 2.8%. ITF is extremely specific and very sensitive for detecting intraoperative CSF leaks. Although false negatives can occur, these patients do not appear to be at risk for postoperative CSF leak. The use of ITF may help surgeons prevent postoperative CSF leaks by intraoperatively detecting and confirming a watertight repair.
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NASA Astrophysics Data System (ADS)
de Oliveira, Helder C. R.; Mencattini, Arianna; Casti, Paola; Martinelli, Eugenio; di Natale, Corrado; Catani, Juliana H.; de Barros, Nestor; Melo, Carlos F. E.; Gonzaga, Adilson; Vieira, Marcelo A. C.
2018-02-01
This paper proposes a method to reduce the number of false-positives (FP) in a computer-aided detection (CAD) scheme for automated detection of architectural distortion (AD) in digital mammography. AD is a subtle contraction of breast parenchyma that may represent an early sign of breast cancer. Due to its subtlety and variability, AD is more difficult to detect compared to microcalcifications and masses, and is commonly found in retrospective evaluations of false-negative mammograms. Several computer-based systems have been proposed for automated detection of AD in breast images. The usual approach is automatically detect possible sites of AD in a mammographic image (segmentation step) and then use a classifier to eliminate the false-positives and identify the suspicious regions (classification step). This paper focus on the optimization of the segmentation step to reduce the number of FPs that is used as input to the classifier. The proposal is to use statistical measurements to score the segmented regions and then apply a threshold to select a small quantity of regions that should be submitted to the classification step, improving the detection performance of a CAD scheme. We evaluated 12 image features to score and select suspicious regions of 74 clinical Full-Field Digital Mammography (FFDM). All images in this dataset contained at least one region with AD previously marked by an expert radiologist. The results showed that the proposed method can reduce the false positives of the segmentation step of the CAD scheme from 43.4 false positives (FP) per image to 34.5 FP per image, without increasing the number of false negatives.
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Assessing environmental DNA detection in controlled lentic systems.
Moyer, Gregory R; Díaz-Ferguson, Edgardo; Hill, Jeffrey E; Shea, Colin
2014-01-01
Little consideration has been given to environmental DNA (eDNA) sampling strategies for rare species. The certainty of species detection relies on understanding false positive and false negative error rates. We used artificial ponds together with logistic regression models to assess the detection of African jewelfish eDNA at varying fish densities (0, 0.32, 1.75, and 5.25 fish/m3). Our objectives were to determine the most effective water stratum for eDNA detection, estimate true and false positive eDNA detection rates, and assess the number of water samples necessary to minimize the risk of false negatives. There were 28 eDNA detections in 324, 1-L, water samples collected from four experimental ponds. The best-approximating model indicated that the per-L-sample probability of eDNA detection was 4.86 times more likely for every 2.53 fish/m3 (1 SD) increase in fish density and 1.67 times less likely for every 1.02 C (1 SD) increase in water temperature. The best section of the water column to detect eDNA was the surface and to a lesser extent the bottom. Although no false positives were detected, the estimated likely number of false positives in samples from ponds that contained fish averaged 3.62. At high densities of African jewelfish, 3-5 L of water provided a >95% probability for the presence/absence of its eDNA. Conversely, at moderate and low densities, the number of water samples necessary to achieve a >95% probability of eDNA detection approximated 42-73 and >100 L, respectively. Potential biases associated with incomplete detection of eDNA could be alleviated via formal estimation of eDNA detection probabilities under an occupancy modeling framework; alternatively, the filtration of hundreds of liters of water may be required to achieve a high (e.g., 95%) level of certainty that African jewelfish eDNA will be detected at low densities (i.e., <0.32 fish/m3 or 1.75 g/m3).
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Breast cancers not detected at MRI: review of false-negative lesions.
Shimauchi, Akiko; Jansen, Sanaz A; Abe, Hiroyuki; Jaskowiak, Nora; Schmidt, Robert A; Newstead, Gillian M
2010-06-01
The objective of our study was to determine the sensitivity of cancer detection at breast MRI using current imaging techniques and to evaluate the characteristics of lesions with false-negative examinations. Two hundred seventeen patients with 222 newly diagnosed breast cancers or highly suspicious breast lesions that were subsequently shown to be malignant underwent breast MRI examinations for staging. Two breast imaging radiologists performed a consensus review of the breast MRI examinations. The absence of perceptible contrast enhancement at the expected site was considered to be a false-negative MRI. Histology of all lesions was reviewed by an experienced breast pathologist. Enhancement was observed in 213 (95.9%) of the 222 cancer lesions. Of the nine lesions without visible enhancement, two lesions were excluded because the entire tumor had been excised at percutaneous biopsy performed before the MRI examination and no residual tumor was noted on the final histology. The overall sensitivity of MRI for the known cancers was 96.8% (213/220); for invasive cancer, 98.3% (176/179); and for ductal carcinoma in situ, 90.2% (37/41). In a population of 220 sequentially diagnosed breast cancer lesions, we found seven (3.2%) MRI-occult cancers, fewer than seen in other published studies. Small tumor size and diffuse parenchymal enhancement were the principal reasons for these false-negative results. Although the overall sensitivity of cancer detection was high (96.8%), it should be emphasized that a negative MRI should not influence the management of a lesion that appears to be of concern on physical examination or on other imaging techniques.
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Simple immunoassay for detection of PCBs in transformer oil.
Glass, Thomas R; Ohmura, Naoya; Taemi, Yukihiro; Joh, Takashi
2005-07-01
A rapid and inexpensive procedure to detect polychlorinated biphenyls (PCBs) in transformer oil is needed to facilitate identification and removal of PCB contaminated transformers. Here we describe a simple two-step liquid-liquid extraction using acidic dimethyl sulfoxide in conjunction with an immunoassay for detecting PCBs in transformer oil. The process described is faster and simpler than any previous immunoassay while maintaining comparable detection limit and false negative rate. Cross reactivity data, characterizing the immunoassay response to the four Kanechlor technical mixtures of PCBs in oil, are presented. Forty-five used transformer oil samples were analyzed by gas chromatography-high-resolution mass spectrometry and were also evaluated using the immunoassay protocol developed. Results presented show zero false negatives at a 1.4 ppm nominal cutoff for the transformer oils analyzed.
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Iguchi, Hiroyoshi; Wada, Tadashi; Matsushita, Naoki; Oishi, Masahiro; Teranishi, Yuichi; Yamane, Hideo
2014-07-01
The accuracy and sensitivity of fine-needle aspiration cytology (FNAC) in this analysis were not satisfactory, and the false-negative rate seemed to be higher than for parotid tumours. The possibility of low-grade malignancy should be considered in the surgical treatment of accessory parotid gland (APG) tumours, even if the preoperative results of FNAC suggest that the tumour is benign. Little is known about the usefulness of FNAC in the preoperative evaluation of APG tumours, probably due to the paucity of APG tumour cases. We examined the usefulness of FNAC in the detection of malignant APG tumours. We conducted a retrospective analysis of 3 cases from our hospital, along with 18 previously reported Japanese cases. We compared the preoperative FNAC results with postoperative histopathological diagnoses of APG tumours and evaluated the accuracy, sensitivity, specificity and false-negative rates of FNAC in detecting malignant APG tumours. There were four false-negative cases (19.0%), three of mucoepidermoid carcinomas and one of malignant lymphoma. One false-positive result was noted in the case of a myoepithelioma, which was cytologically diagnosed as suspected adenoid cystic carcinoma. The accuracy, sensitivity and specificity of FNAC in detecting malignant tumours were 76.2%, 60.0% and 90.9%, respectively.
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Robust Detection of Rare Species Using Environmental DNA: The Importance of Primer Specificity
Wilcox, Taylor M.; McKelvey, Kevin S.; Young, Michael K.; Jane, Stephen F.; Lowe, Winsor H.; Whiteley, Andrew R.; Schwartz, Michael K.
2013-01-01
Environmental DNA (eDNA) is being rapidly adopted as a tool to detect rare animals. Quantitative PCR (qPCR) using probe-based chemistries may represent a particularly powerful tool because of the method’s sensitivity, specificity, and potential to quantify target DNA. However, there has been little work understanding the performance of these assays in the presence of closely related, sympatric taxa. If related species cause any cross-amplification or interference, false positives and negatives may be generated. These errors can be disastrous if false positives lead to overestimate the abundance of an endangered species or if false negatives prevent detection of an invasive species. In this study we test factors that influence the specificity and sensitivity of TaqMan MGB assays using co-occurring, closely related brook trout (Salvelinus fontinalis) and bull trout (S. confluentus) as a case study. We found qPCR to be substantially more sensitive than traditional PCR, with a high probability of detection at concentrations as low as 0.5 target copies/µl. We also found that number and placement of base pair mismatches between the Taqman MGB assay and non-target templates was important to target specificity, and that specificity was most influenced by base pair mismatches in the primers, rather than in the probe. We found that insufficient specificity can result in both false positive and false negative results, particularly in the presence of abundant related species. Our results highlight the utility of qPCR as a highly sensitive eDNA tool, and underscore the importance of careful assay design. PMID:23555689
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Robust detection of rare species using environmental DNA: the importance of primer specificity.
Wilcox, Taylor M; McKelvey, Kevin S; Young, Michael K; Jane, Stephen F; Lowe, Winsor H; Whiteley, Andrew R; Schwartz, Michael K
2013-01-01
Environmental DNA (eDNA) is being rapidly adopted as a tool to detect rare animals. Quantitative PCR (qPCR) using probe-based chemistries may represent a particularly powerful tool because of the method's sensitivity, specificity, and potential to quantify target DNA. However, there has been little work understanding the performance of these assays in the presence of closely related, sympatric taxa. If related species cause any cross-amplification or interference, false positives and negatives may be generated. These errors can be disastrous if false positives lead to overestimate the abundance of an endangered species or if false negatives prevent detection of an invasive species. In this study we test factors that influence the specificity and sensitivity of TaqMan MGB assays using co-occurring, closely related brook trout (Salvelinus fontinalis) and bull trout (S. confluentus) as a case study. We found qPCR to be substantially more sensitive than traditional PCR, with a high probability of detection at concentrations as low as 0.5 target copies/µl. We also found that number and placement of base pair mismatches between the Taqman MGB assay and non-target templates was important to target specificity, and that specificity was most influenced by base pair mismatches in the primers, rather than in the probe. We found that insufficient specificity can result in both false positive and false negative results, particularly in the presence of abundant related species. Our results highlight the utility of qPCR as a highly sensitive eDNA tool, and underscore the importance of careful assay design.
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Ibañez-Sanz, Gemma; Garcia, Montse; Milà, Núria; Rodríguez-Moranta, Francisco; Binefa, Gemma; Gómez-Matas, Javier; Benito, Llúcia; Padrol, Isabel; Barenys, Mercè; Moreno, Victor
2017-09-01
The aim of this study was to analyse false-negative (FN) results of the faecal immunochemical test (FIT) and its determinants in a colorectal cancer screening programme in Catalonia. We carried out a cross-sectional study among 218 screenees with a negative FIT result who agreed to undergo a colonoscopy. A false-negative result was defined as the detection, at colonoscopy, of intermediate/high-risk polyps or colorectal cancer in a patient with a previous negative FIT (<20 µgHb/g). Multivariate logistic regression models were constructed to identify sociodemographic (sex, age) and screening variables (quantitative faecal haemoglobin, colonoscopy findings) related to FN results. Adjusted odds ratios and their 95% confidence intervals were estimated. There were 15.6% FN FIT results. Faecal haemoglobin was undetected in 45.5% of these results and was below 4 µgHb/g in 94.0% of the individuals with a FN result. About 60% of the lesions were located in the proximal colon, whereas the expected percentage was 30%. Decreasing the positivity threshold of FIT does not increase the detection rate of advanced neoplasia, but may increase the costs and potential adverse effects.
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Risk of breast cancer after false-positive results in mammographic screening.
Román, Marta; Castells, Xavier; Hofvind, Solveig; von Euler-Chelpin, My
2016-06-01
Women with false-positive results are commonly referred back to routine screening. Questions remain regarding their long-term outcome of breast cancer. We assessed the risk of screen-detected breast cancer in women with false-positive results. We conducted a joint analysis using individual level data from the population-based screening programs in Copenhagen and Funen in Denmark, Norway, and Spain. Overall, 150,383 screened women from Denmark (1991-2008), 612,138 from Norway (1996-2010), and 1,172,572 from Spain (1990-2006) were included. Poisson regression was used to estimate the relative risk (RR) of screen-detected cancer for women with false-positive versus negative results. We analyzed information from 1,935,093 women 50-69 years who underwent 6,094,515 screening exams. During an average 5.8 years of follow-up, 230,609 (11.9%) women received a false-positive result and 27,849 (1.4%) were diagnosed with screen-detected cancer. The adjusted RR of screen-detected cancer after a false-positive result was 2.01 (95% CI: 1.93-2.09). Women who tested false-positive at first screen had a RR of 1.86 (95% CI: 1.77-1.96), whereas those who tested false-positive at third screening had a RR of 2.42 (95% CI: 2.21-2.64). The RR of breast cancer at the screening test after the false-positive result was 3.95 (95% CI: 3.71-4.21), whereas it decreased to 1.25 (95% CI: 1.17-1.34) three or more screens after the false-positive result. Women with false-positive results had a twofold risk of screen-detected breast cancer compared to women with negative tests. The risk remained significantly higher three or more screens after the false-positive result. The increased risk should be considered when discussing stratified screening strategies. © 2016 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.
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Taylor, Darlene; Durigon, Monica; Davis, Heather; Archibald, Chris; Konrad, Bernhard; Coombs, Daniel; Gilbert, Mark; Cook, Darrel; Krajden, Mel; Wong, Tom; Ogilvie, Gina
2015-03-01
Failure to understand the risk of false-negative HIV test results during the window period results in anxiety. Patients typically want accurate test results as soon as possible while clinicians prefer to wait until the probability of a false-negative is virtually nil. This review summarizes the median window periods for third-generation antibody and fourth-generation HIV tests and provides the probability of a false-negative result for various days post-exposure. Data were extracted from published seroconversion panels. A 10-day eclipse period was used to estimate days from infection to first detection of HIV RNA. Median (interquartile range) days to seroconversion were calculated and probabilities of a false-negative result at various time periods post-exposure are reported. The median (interquartile range) window period for third-generation tests was 22 days (19-25) and 18 days (16-24) for fourth-generation tests. The probability of a false-negative result is 0.01 at 80 days' post-exposure for third-generation tests and at 42 days for fourth-generation tests. The table of probabilities of falsely-negative HIV test results may be useful during pre- and post-test HIV counselling to inform co-decision making regarding the ideal time to test for HIV. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
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Gubern-Mérida, Albert; Vreemann, Suzan; Martí, Robert; Melendez, Jaime; Lardenoije, Susanne; Mann, Ritse M; Karssemeijer, Nico; Platel, Bram
2016-02-01
To evaluate the performance of an automated computer-aided detection (CAD) system to detect breast cancers that were overlooked or misinterpreted in a breast MRI screening program for women at increased risk. We identified 40 patients that were diagnosed with breast cancer in MRI and had a prior MRI examination reported as negative available. In these prior examinations, 24 lesions could retrospectively be identified by two breast radiologists in consensus: 11 were scored as visible and 13 as minimally visible. Additionally, 120 normal scans were collected from 120 women without history of breast cancer or breast surgery participating in the same MRI screening program. A fully automated CAD system was applied to this dataset to detect malignant lesions. At 4 false-positives per normal case, the sensitivity for the detection of cancer lesions that were visible or minimally visible in retrospect in prior-negative examinations was 0.71 (95% CI=0.38-1.00) and 0.31 (0.07-0.59), respectively. A substantial proportion of cancers that were misinterpreted or overlooked in an MRI screening program was detected by a CAD system in prior-negative examinations. It has to be clarified with further studies if such a CAD system has an influence on the number of misinterpreted and overlooked cancers in clinical practice when results are given to a radiologist. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
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Colonic polyps: application value of computer-aided detection in computed tomographic colonography.
Zhang, Hui-Mao; Guo, Wei; Liu, Gui-Feng; An, Dong-Hong; Gao, Shuo-Hui; Sun, Li-Bo; Yang, Hai-Shan
2011-02-01
Colonic polyps are frequently encountered in clinics. Computed tomographic colonography (CTC), as a painless and quick detection, has high values in clinics. In this study, we evaluated the application value of computer-aided detection (CAD) in CTC detection of colonic polyps in the Chinese population. CTC was performed with a GE 64-row multidetector computed tomography (MDCT) scanner. Data of 50 CTC patients (39 patients positive for at least one polyp of ≥ 0.5 cm in size and the other 11 patients negative by endoscopic detection) were retrospectively reviewed first without computer-aided detection (CAD) and then with CAD by four radiologists (two were experienced and another two inexperienced) blinded to colonoscopy findings. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of detected colonic polyps, as well as the areas under the ROC curves (Az value) with and without CAD were calculated. CAD increased the overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the colonic polyps detected by experienced and inexperienced readers. The sensitivity in detecting small polyps (5 - 9 mm) with CAD in experienced and inexperienced readers increased from 82% and 44% to 93% and 82%, respectively (P > 0.05 and P < 0.001). With the use of CAD, the overall false positive rate and false negative rate for the detection of polyps by experienced and inexperienced readers decreased in different degrees. Among 13 sessile polyps not detected by CAD, two were ≥ 1.0 cm, eleven were 5 - 9 mm in diameter, and nine were flat-shaped lesions. The application of CAD in combination with CTC can increase the ability to detect colonic polyps, particularly for inexperienced readers. However, CAD is of limited value for the detection of flat polyps.
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High false-negative rate of anti-HCV among Egyptian patients on regular hemodialysis.
El-Sherif, Assem; Elbahrawy, Ashraf; Aboelfotoh, Atef; Abdelkarim, Magdy; Saied Mohammad, Abdel-Gawad; Abdallah, Abdallah Mahmoud; Mostafa, Sadek; Elmestikawy, Amr; Elwassief, Ahmed; Salah, Mohamed; Abdelbaseer, Mohamed Ali; Abdelwahab, Kouka Saadeldin
2012-07-01
Routine serological testing for hepatitis C virus (HCV) infection among hemodialysis (HD) patients is currently recommended. A dilemma existed on the value of serology because some investigators reported a high rate of false-negative serologic testing. In this study, we aimed to detect the false-negative rate of anti-HCV among Egyptian HD patients. Seventy-eight HD patients, negative for anti-HCV, anti-HIV, and hepatitis B surface antigen, were tested for HCV RNA by reverse transcriptase polymerase chain reaction (RT-PCR). In the next step, the viral load was quantified by real-time PCR in RT-PCR-positive patients. Risk factors for HCV infection, as well as clinical and biochemical indicators of liver disease, were compared between false-negative and true-negative anti-HCV HD patients. The frequency of false-negative anti-HCV was 17.9%. Frequency of blood transfusion, duration of HD, dialysis at multiple centers, and diabetes mellitus were not identified as risk factors for HCV infection. The frequency of false-negative results had a linear relation to the prevalence of HCV infection in the HD units. Timely identification of HCV within dialysis units is needed in order to lower the risk of HCV spread within the HD units. The high false-negative rate of anti-HCV among HD patients in our study justifies testing of a large scale of patients for precious assessment of effectiveness of nucleic acid amplification technology testing in screening HD patient. © 2012 The Authors. Hemodialysis International © 2012 International Society for Hemodialysis.
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Noninvasive Electromagnetic Detection of Bladder Cancer
Cormio, Luigi; Vedruccio, Clarbruno; Leucci, Giorgio; Massenio, Paolo; Di Fino, Giuseppe; Cavaliere, Vincenzo; Carrieri, Giuseppe
2014-01-01
Objectives. Normal and neoplastic human tissues have different electromagnetic properties. This study aimed to determine the diagnostic accuracy of noninvasive electromagnetic detection of bladder cancer (BC) by the tissue-resonance interaction method (TRIM-prob). Patients and Methods. Consecutive patients were referred for cystoscopy because of (i) microscopic or gross hematuria and/or irritative voiding symptoms and (ii) bladder ultrasounds and urinary cytology findings negative or just suspicious of malignancy. Patients were first submitted to TRIM-prob bladder scanning by a single investigator and then to cystoscopy by another investigator blind to TRIM-prob data. Results. In 125 evaluated patients cystoscopy was positive for BC in 47 and negative in the remaining 78; conversely, TRIM-prob bladder scanning was positive for BC in 53 and negative in 72. In particular, TRIM-prob scanning yielded 7 false positives and only one false negative; therefore, its overall sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were 97.9%, 89.9%, 86.8%, 98.6%, and 93.6%, respectively. Conclusions. TRIM-prob bladder scanning was a simple and quite accurate method for non-invasive electromagnetic detection of BC. If the elevated positive and negative predictive values will be replicated in further well-designed studies, it could be used to screen asymptomatic patients at high risk of BC. PMID:24563795
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Experimental investigation of false positive errors in auditory species occurrence surveys
Miller, David A.W.; Weir, Linda A.; McClintock, Brett T.; Grant, Evan H. Campbell; Bailey, Larissa L.; Simons, Theodore R.
2012-01-01
False positive errors are a significant component of many ecological data sets, which in combination with false negative errors, can lead to severe biases in conclusions about ecological systems. We present results of a field experiment where observers recorded observations for known combinations of electronically broadcast calling anurans under conditions mimicking field surveys to determine species occurrence. Our objectives were to characterize false positive error probabilities for auditory methods based on a large number of observers, to determine if targeted instruction could be used to reduce false positive error rates, and to establish useful predictors of among-observer and among-species differences in error rates. We recruited 31 observers, ranging in abilities from novice to expert, that recorded detections for 12 species during 180 calling trials (66,960 total observations). All observers made multiple false positive errors and on average 8.1% of recorded detections in the experiment were false positive errors. Additional instruction had only minor effects on error rates. After instruction, false positive error probabilities decreased by 16% for treatment individuals compared to controls with broad confidence interval overlap of 0 (95% CI: -46 to 30%). This coincided with an increase in false negative errors due to the treatment (26%; -3 to 61%). Differences among observers in false positive and in false negative error rates were best predicted by scores from an online test and a self-assessment of observer ability completed prior to the field experiment. In contrast, years of experience conducting call surveys was a weak predictor of error rates. False positive errors were also more common for species that were played more frequently, but were not related to the dominant spectral frequency of the call. Our results corroborate other work that demonstrates false positives are a significant component of species occurrence data collected by auditory methods. Instructing observers to only report detections they are completely certain are correct is not sufficient to eliminate errors. As a result, analytical methods that account for false positive errors will be needed, and independent testing of observer ability is a useful predictor for among-observer variation in observation error rates.
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Application of Immunosignatures for Diagnosis of Valley Fever
Navalkar, Krupa Arun; Johnston, Stephen Albert; Woodbury, Neal; Galgiani, John N.; Magee, D. Mitchell; Chicacz, Zbigniew
2014-01-01
Valley fever (VF) is difficult to diagnose, partly because the symptoms of VF are confounded with those of other community-acquired pneumonias. Confirmatory diagnostics detect IgM and IgG antibodies against coccidioidal antigens via immunodiffusion (ID). The false-negative rate can be as high as 50% to 70%, with 5% of symptomatic patients never showing detectable antibody levels. In this study, we tested whether the immunosignature diagnostic can resolve VF false negatives. An immunosignature is the pattern of antibody binding to random-sequence peptides on a peptide microarray. A 10,000-peptide microarray was first used to determine whether valley fever patients can be distinguished from 3 other cohorts with similar infections. After determining the VF-specific peptides, a small 96-peptide diagnostic array was created and tested. The performances of the 10,000-peptide array and the 96-peptide diagnostic array were compared to that of the ID diagnostic standard. The 10,000-peptide microarray classified the VF samples from the other 3 infections with 98% accuracy. It also classified VF false-negative patients with 100% sensitivity in a blinded test set versus 28% sensitivity for ID. The immunosignature microarray has potential for simultaneously distinguishing valley fever patients from those with other fungal or bacterial infections. The same 10,000-peptide array can diagnose VF false-negative patients with 100% sensitivity. The smaller 96-peptide diagnostic array was less specific for diagnosing false negatives. We conclude that the performance of the immunosignature diagnostic exceeds that of the existing standard, and the immunosignature can distinguish related infections and might be used in lieu of existing diagnostics. PMID:24964807
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NASA Astrophysics Data System (ADS)
Pietrzyk, Mariusz W.; Donovan, Tim; Brennan, Patrick C.; Dix, Alan; Manning, David J.
2011-03-01
Aim: To optimize automated classification of radiological errors during lung nodule detection from chest radiographs (CxR) using a support vector machine (SVM) run on the spatial frequency features extracted from the local background of selected regions. Background: The majority of the unreported pulmonary nodules are visually detected but not recognized; shown by the prolonged dwell time values at false-negative regions. Similarly, overestimated nodule locations are capturing substantial amounts of foveal attention. Spatial frequency properties of selected local backgrounds are correlated with human observer responses either in terms of accuracy in indicating abnormality position or in the precision of visual sampling the medical images. Methods: Seven radiologists participated in the eye tracking experiments conducted under conditions of pulmonary nodule detection from a set of 20 postero-anterior CxR. The most dwelled locations have been identified and subjected to spatial frequency (SF) analysis. The image-based features of selected ROI were extracted with un-decimated Wavelet Packet Transform. An analysis of variance was run to select SF features and a SVM schema was implemented to classify False-Negative and False-Positive from all ROI. Results: A relative high overall accuracy was obtained for each individually developed Wavelet-SVM algorithm, with over 90% average correct ratio for errors recognition from all prolonged dwell locations. Conclusion: The preliminary results show that combined eye-tracking and image-based features can be used for automated detection of radiological error with SVM. The work is still in progress and not all analytical procedures have been completed, which might have an effect on the specificity of the algorithm.
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Renshaw, A A; Lezon, K M; Wilbur, D C
2001-04-25
Routine quality control rescreening often is used to calculate the false-negative rate (FNR) of gynecologic cytology. Theoretic analysis suggests that this is not appropriate, due to the high FNR of rescreening and the inability to actually measure it. The authors sought to determine the FNR of manual rescreening in a large, prospective, two-arm clinical trial using an analytic instrument in the evaluation. The results of the Autopap System Clinical Trial, encompassing 25,124 analyzed slides, were reviewed. The false-negative and false-positive rates at various thresholds were determined for routine primary screening, routine rescreening, Autopap primary screening, and Autopap rescreening by using a simple, standard methodology. The FNR of routine manual rescreening at the level of atypical squamous cells of undetermined significance (ASCUS) was 73%, more than 3 times the FNR of primary screening; 11 cases were detected. The FNR of Autopap rescreening was 34%; 80 cases were detected. Routine manual rescreening decreased the laboratory FNR by less than 1%; Autopap rescreening reduced the overall laboratory FNR by 5.7%. At the same time, the false-positive rate for Autopap screening was significantly less than that of routine manual screening at the ASCUS level (4.7% vs. 5.6%; P < 0.0001). Rescreening with the Autopap system remained more sensitive than manual rescreening at the low grade squamous intraepithelial lesions threshold (FNR of 58.8% vs. 100%, respectively), although the number of cases rescreened was low. Routine manual rescreening cannot be used to calculate the FNR of primary screening. Routine rescreening is an extremely ineffective method to detect error and thereby decrease a laboratory's FNR. The Autopap system is a much more effective way of detecting errors within a laboratory and reduces the laboratory's FNR by greater than 25%.
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Sentinel lymph node detection in patients with early cervical cancer.
Acharya, B C; Jihong, L
2009-01-01
Lymph node status is the most important independent prognostic factor in early stage cervical cancer. Intraoperative lymphatic mapping and sentinel lymph node detection have been increasingly evaluated in the treatment of a variety of solid tumors, particularly breast cancer and cutaneous melanoma. This study evaluated the feasibility of these procedures in patients undergoing radical hysterectomy with pelvic lymphadenectomy for early cervical cancer. A total of 30 patients with histologically diagnosed FIGO stage IA to IIA cervical cancer were enrolled to this study. They were scheduled to undergo radical abdominal hysterectomy and pelvic lymphadenectomy after injecting patent blue dye in cervix. A total of 60 SLNs (mean 2.5) were detected in 24 patients with detection rate of 80%. Bilateral SLNs were detected in 70.1% of cases. SLNs were identified in obturator and external iliac areas in 50% and 31.7%, respectively; no SLNs were discovered in the common iliac region. Seven patients (23.3%) had lymph node metastases; one of these had false negative SLN.The false negative rate and negative predictive value were 14.3% and 94.4%, respectively. SLN detection procedure with blue dye technique is a feasible procedure in cervical cancer. Patent blue dye is cheap, safe and effective tracer to detect sentinel node in carcinoma of cervix.
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Xu, Xiaodan; Li, Yingcong; Zhao, Heng; Wen, Si-yuan; Wang, Sheng-qi; Huang, Jian; Huang, Kun-lun; Luo, Yun-bo
2005-05-18
To devise a rapid and reliable method for the detection and identification of genetically modified (GM) events, we developed a multiplex polymerase chain reaction (PCR) coupled with a DNA microarray system simultaneously aiming at many targets in a single reaction. The system included probes for screening gene, species reference gene, specific gene, construct-specific gene, event-specific gene, and internal and negative control genes. 18S rRNA was combined with species reference genes as internal controls to assess the efficiency of all reactions and to eliminate false negatives. Two sets of the multiplex PCR system were used to amplify four and five targets, respectively. Eight different structure genes could be detected and identified simultaneously for Roundup Ready soybean in a single microarray. The microarray specificity was validated by its ability to discriminate two GM maizes Bt176 and Bt11. The advantages of this method are its high specificity and greatly reduced false-positives and -negatives. The multiplex PCR coupled with microarray technology presented here is a rapid and reliable tool for the simultaneous detection of GM organism ingredients.
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NASA Astrophysics Data System (ADS)
Wang, Jing; Feng, Shangyuan; Lin, Juqiang; Zeng, Yongyi; Li, Ling; Huang, Zufang; Li, Buhong; Zeng, Haishan; Chen, Rong
2013-11-01
Surface-enhanced Raman spectroscopy (SERS) of serum albumin and globulin were employed to detect hepatocellular carcinoma (HCC). Tentative assignments of SERS bands show specific biomolecular changes associated with cancer development. These changes include a decrease in relative amounts of tryptophan, glutamine, glycine, and serine, indicating excessive consumption of amino acids for protein duplication. Principal component analysis was also introduced to analyze the obtained spectra, resulting in both diagnostic sensitivity and specificity of 100%. More importantly, it reveals that this method can detect HCC patients with alpha-fetoprotein negative test results, suggesting its great potential as a new alternative to detect HCC.
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Jeremiah, S S; Balaji, V; Anandan, S; Sahni, R D
2014-01-01
The modified Hodge test (MHT) is widely used as a screening test for the detection of carbapenemases in Gram-negative bacteria. This test has several pitfalls in terms of validity and interpretation. Also the test has a very low sensitivity in detecting the New Delhi metallo-β-lactamase (NDM). Considering the degree of dissemination of the NDM and the growing pandemic of carbapenem resistance, a more accurate alternative test is needed at the earliest. The study intends to compare the performance of the MHT with the commercially available Neo-Sensitabs - Carbapenemases/Metallo-β-Lactamase (MBL) Confirmative Identification pack to find out whether the latter could be an efficient alternative to the former. A total of 105 isolates of Klebsiella pneumoniae resistant to imipenem and meropenem, collected prospectively over a period of 2 years were included in the study. The study isolates were tested with the MHT, the Neo-Sensitabs - Carbapenemases/MBL Confirmative Identification pack and polymerase chain reaction (PCR) for detecting the blaNDM-1 gene. Among the 105 isolates, the MHT identified 100 isolates as carbapenemase producers. In the five isolates negative for the MHT, four were found to produce MBLs by the Neo-Sensitabs. The Neo-Sensitabs did not have any false negatives when compared against the PCR. The MHT can give false negative results, which lead to failure in detecting the carbapenemase producers. Also considering the other pitfalls of the MHT, the Neo-Sensitabs--Carbapenemases/MBL Confirmative Identification pack could be a more efficient alternative for detection of carbapenemase production in Gram-negative bacteria.
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Robotic CCD microscope for enhanced crystal recognition
Segelke, Brent W.; Toppani, Dominique
2007-11-06
A robotic CCD microscope and procedures to automate crystal recognition. The robotic CCD microscope and procedures enables more accurate crystal recognition, leading to fewer false negative and fewer false positives, and enable detection of smaller crystals compared to other methods available today.
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Methods for threshold determination in multiplexed assays
Tammero, Lance F. Bentley; Dzenitis, John M; Hindson, Benjamin J
2014-06-24
Methods for determination of threshold values of signatures comprised in an assay are described. Each signature enables detection of a target. The methods determine a probability density function of negative samples and a corresponding false positive rate curve. A false positive criterion is established and a threshold for that signature is determined as a point at which the false positive rate curve intersects the false positive criterion. A method for quantitative analysis and interpretation of assay results together with a method for determination of a desired limit of detection of a signature in an assay are also described.
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Bartels, Mette Damkjaer; Boye, Kit; Rohde, Susanne Mie; Larsen, Anders Rhod; Torfs, Herbert; Bouchy, Peggy; Skov, Robert; Westh, Henrik
2009-05-01
Rapid tests for detection of methicillin-resistant Staphylococcus aureus (MRSA) carriage are important to limit the transmission of MRSA in the health care setting. We evaluated the performance of the BD GeneOhm MRSA real-time PCR assay using a diverse collection of MRSA isolates, mainly from Copenhagen, Denmark, but also including international isolates, e.g., USA100-1100. Pure cultures of 349 MRSA isolates representing variants of staphylococcal cassette chromosome mec (SCCmec) types I to V and 103 different staphylococcal protein A (spa) types were tested. In addition, 53 methicillin-susceptible Staphylococcus aureus isolates were included as negative controls. Forty-four MRSA isolates were undetectable; of these, 95% harbored SCCmec type IVa, and these included the most-common clone in Copenhagen, spa t024-sequence type 8-IVa. The false-negative MRSA isolates were tested with new primers (analyte-specific reagent [ASR] BD GeneOhm MRSA assay) supplied by Becton Dickinson (BD). The ASR BD GeneOhm MRSA assay detected 42 of the 44 isolates that were false negative in the BD GeneOhm MRSA assay. Combining the BD GeneOhm MRSA assay with the ASR BD GeneOhm MRSA assay greatly improved the results, with only two MRSA isolates being false negative. The BD GeneOhm MRSA assay alone is not adequate for MRSA detection in Copenhagen, Denmark, as more than one-third of our MRSA isolates would not be detected. We recommend that the BD GeneOhm MRSA assay be evaluated against the local MRSA diversity before being established as a standard assay, and due to the constant evolution of SCCmec cassettes, a continuous global surveillance is advisable in order to update the assay as necessary.
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Histoplasma Urinary Antigen Testing Obviates the Need for Coincident Serum Antigen Testing.
Libert, Diane; Procop, Gary W; Ansari, Mohammad Q
2018-03-07
Serum and urine antigen (SAg, UAg) detection are common tests for Histoplasma capsulatum. UAg detection is more widely used and reportedly has a higher sensitivity. We investigated whether SAg detection contributes meaningfully to the initial evaluation of patients with suspected histoplasmosis. We reviewed 20,285 UAg and 1,426 SAg tests ordered from 1997 to 2016 and analyzed paired UAg and SAg tests completed on the same patient within 1 week. We determined the positivity rate for each test. Of 601 paired specimens, 542 were concurrent negatives and 48 were concurrent positives (98% agreement). Medical records were available for eight of 11 pairs with discrepant results. UAg was falsely positive in six instances, truly positive once, and falsely negative once. These findings support using a single antigen detection test, rather than both UAg and SAg, as an initial screen for suspected histoplasmosis. This aligns with the current practice of most physicians.
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Park, So Yoon; Choi, Ji Soo; Han, Boo-Kyung; Ko, Eun Young; Ko, Eun Sook
2017-09-01
To investigate factors related to false shear wave elastography (SWE) results for breast non-mass lesions (NMLs) detected by B-mode US. This retrospective study enrolled 152 NMLs detected by B-mode US and later pathologically confirmed (79 malignant, 73 benign). All lesions underwent B-mode US and SWE. Quantitative (mean elasticity [E mean ]) and qualitative (maximum stiffness colour) SWE parameters were assessed, and 'E mean > 85.1 kPa' or 'stiff colour (green to red)' determined malignancy. Final SWE results were matched to pathology results. Multivariate logistic regression analysis identified factors associated with false SWE results for diagnosis of breast NMLs. Associated calcifications (E mean : odds ratio [OR] = 7.60, P < 0.01; maximum stiffness colour: OR = 6.30, P = 0.02), in situ cancer compared to invasive cancer (maximum stiffness colour: OR = 5.29, P = 0.02), and lesion size (E mean : OR = 0.90, P < 0.01; maximum stiffness colour: OR = 0.91, P = 0.01) were significantly associated with false negative SWE results for malignant NMLs. Distance from the nipple (E mean : OR = 0.84, P = 0.03; maximum stiffness colour: OR = 0.93, P = 0.04) was significantly associated with false positive SWE results for benign NMLs. Presence of associated calcifications, absence of the invasive component, and smaller lesion size for malignant NMLs and shorter distance from the nipple for benign NMLs are factors significantly associated with false SWE results. • Calcification and size are associated with false negative SWE in malignant NMLs. • In situ cancer is associated with false negative SWE in malignant NMLs. • Distance from the nipple is associated with false positive SWE in benign NMLs. • These factors need consideration when performing SWE on breast NMLs.
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Experimental investigation of observation error in anuran call surveys
McClintock, B.T.; Bailey, L.L.; Pollock, K.H.; Simons, T.R.
2010-01-01
Occupancy models that account for imperfect detection are often used to monitor anuran and songbird species occurrence. However, presenceabsence data arising from auditory detections may be more prone to observation error (e.g., false-positive detections) than are sampling approaches utilizing physical captures or sightings of individuals. We conducted realistic, replicated field experiments using a remote broadcasting system to simulate simple anuran call surveys and to investigate potential factors affecting observation error in these studies. Distance, time, ambient noise, and observer abilities were the most important factors explaining false-negative detections. Distance and observer ability were the best overall predictors of false-positive errors, but ambient noise and competing species also affected error rates for some species. False-positive errors made up 5 of all positive detections, with individual observers exhibiting false-positive rates between 0.5 and 14. Previous research suggests false-positive errors of these magnitudes would induce substantial positive biases in standard estimators of species occurrence, and we recommend practices to mitigate for false positives when developing occupancy monitoring protocols that rely on auditory detections. These recommendations include additional observer training, limiting the number of target species, and establishing distance and ambient noise thresholds during surveys. ?? 2010 The Wildlife Society.
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Sample Selection for Training Cascade Detectors.
Vállez, Noelia; Deniz, Oscar; Bueno, Gloria
2015-01-01
Automatic detection systems usually require large and representative training datasets in order to obtain good detection and false positive rates. Training datasets are such that the positive set has few samples and/or the negative set should represent anything except the object of interest. In this respect, the negative set typically contains orders of magnitude more images than the positive set. However, imbalanced training databases lead to biased classifiers. In this paper, we focus our attention on a negative sample selection method to properly balance the training data for cascade detectors. The method is based on the selection of the most informative false positive samples generated in one stage to feed the next stage. The results show that the proposed cascade detector with sample selection obtains on average better partial AUC and smaller standard deviation than the other compared cascade detectors.
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Is screening with digital imaging using one retinal view adequate?
Herbert, H M; Jordan, K; Flanagan, D W
2003-05-01
To compare the detection of diabetic retinopathy from digital images with slit-lamp biomicroscopy, and to determine whether British Diabetic Association (BDA) screening criteria are attained (>80% sensitivity, >95% specificity, &<5% technical failure). Diabetics referred for screening were studied in a prospective fashion. A single 45 degrees fundus image was obtained using the nonmydriatic digital camera. Each patient subsequently underwent slit-lamp biomicroscopy and diabetic retinopathy grading by a consultant ophthalmologist. Diabetic retinopathy and maculopathy was graded according to the Early Treatment of Diabetic Retinopathy Study. A total of 145 patients (288 eyes) were identified for screening. Of these, 26% of eyes had diabetic retinopathy, and eight eyes (3%) had sight-threatening diabetic retinopathy requiring treatment. The sensitivity for detection of any diabetic retinopathy was 38% and the specificity 95%. There was a 4% technical failure rate. There were 42/288 false negatives and 10/288 false positives. Of the 42 false negatives, 18 represented diabetic maculopathy, 20 represented peripheral diabetic retinopathy and four eyes had both macular and peripheral changes. Three eyes in the false-negative group (1% of total eyes) had sight-threatening retinopathy. There was good concordance between the two consultants (79% agreement on slit-lamp biomicroscopy and 84% on digital image interpretation). The specificity value and technical failure rate compare favourably with BDA guidelines. The low sensitivity for detection of any retinopathy reflects failure to detect minimal maculopathy and retinopathy outside the 45 degrees image. This could be improved by an additional nasal image and careful evaluation of macular images with a low threshold for slit-lamp biomicroscopy if image quality is poor.
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Crompot, Emerence; Van Damme, Michael; Duvillier, Hugues; Pieters, Karlien; Vermeesch, Marjorie; Perez-Morga, David; Meuleman, Nathalie; Mineur, Philippe; Bron, Dominique; Lagneaux, Laurence; Stamatopoulos, Basile
2015-01-01
Microparticles (MPs), also called microvesicles (MVs) are plasma membrane-derived fragments with sizes ranging from 0.1 to 1μm. Characterization of these MPs is often performed by flow cytometry but there is no consensus on the appropriate negative control to use that can lead to false positive results. We analyzed MPs from platelets, B-cells, T-cells, NK-cells, monocytes, and chronic lymphocytic leukemia (CLL) B-cells. Cells were purified by positive magnetic-separation and cultured for 48h. Cells and MPs were characterized using the following monoclonal antibodies (CD19,20 for B-cells, CD3,8,5,27 for T-cells, CD16,56 for NK-cells, CD14,11c for monocytes, CD41,61 for platelets). Isolated MPs were stained with annexin-V-FITC and gated between 300nm and 900nm. The latex bead technique was then performed for easy detection of MPs. Samples were analyzed by Transmission (TEM) and Scanning Electron microscopy (SEM). Annexin-V positive events within a gate of 300-900nm were detected and defined as MPs. Our results confirmed that the characteristic antigens CD41/CD61 were found on platelet-derived-MPs validating our technique. However, for MPs derived from other cell types, we were unable to detect any antigen, although they were clearly expressed on the MP-producing cells in the contrary of several data published in the literature. Using the latex bead technique, we confirmed detection of CD41,61. However, the apparent expression of other antigens (already deemed positive in several studies) was determined to be false positive, indicated by negative controls (same labeling was used on MPs from different origins). We observed that mother cell antigens were not always detected on corresponding MPs by direct flow cytometry or latex bead cytometry. Our data highlighted that false positive results could be generated due to antibody aspecificity and that phenotypic characterization of MPs is a difficult field requiring the use of several negative controls.
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Crompot, Emerence; Van Damme, Michael; Duvillier, Hugues; Pieters, Karlien; Vermeesch, Marjorie; Perez-Morga, David; Meuleman, Nathalie; Mineur, Philippe; Bron, Dominique; Lagneaux, Laurence; Stamatopoulos, Basile
2015-01-01
Background Microparticles (MPs), also called microvesicles (MVs) are plasma membrane-derived fragments with sizes ranging from 0.1 to 1μm. Characterization of these MPs is often performed by flow cytometry but there is no consensus on the appropriate negative control to use that can lead to false positive results. Materials and Methods We analyzed MPs from platelets, B-cells, T-cells, NK-cells, monocytes, and chronic lymphocytic leukemia (CLL) B-cells. Cells were purified by positive magnetic-separation and cultured for 48h. Cells and MPs were characterized using the following monoclonal antibodies (CD19,20 for B-cells, CD3,8,5,27 for T-cells, CD16,56 for NK-cells, CD14,11c for monocytes, CD41,61 for platelets). Isolated MPs were stained with annexin-V-FITC and gated between 300nm and 900nm. The latex bead technique was then performed for easy detection of MPs. Samples were analyzed by Transmission (TEM) and Scanning Electron microscopy (SEM). Results Annexin-V positive events within a gate of 300-900nm were detected and defined as MPs. Our results confirmed that the characteristic antigens CD41/CD61 were found on platelet-derived-MPs validating our technique. However, for MPs derived from other cell types, we were unable to detect any antigen, although they were clearly expressed on the MP-producing cells in the contrary of several data published in the literature. Using the latex bead technique, we confirmed detection of CD41,61. However, the apparent expression of other antigens (already deemed positive in several studies) was determined to be false positive, indicated by negative controls (same labeling was used on MPs from different origins). Conclusion We observed that mother cell antigens were not always detected on corresponding MPs by direct flow cytometry or latex bead cytometry. Our data highlighted that false positive results could be generated due to antibody aspecificity and that phenotypic characterization of MPs is a difficult field requiring the use of several negative controls. PMID:25978814
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Hocagil, Hilal; Hocagil, Abdullah Cüneyt; Karacabey, Sinan; Akkaya, Tuğba; Şimşek, Gözde; Sanrı, Erkman
2015-09-01
This study aimed to discuss the effectiveness of Pneumoscan working with micropower impulse radar (MIR) technology in diagnosing pneumothorax (PTX) in the emergency department. Patients with suspicion of PTX and indication for thorax tomography (CT) were included into the study. Findings of the Thorax CT were compared with the results of Pneumoscan. Chi-square and Fisher's exact tests were used in categorical variables. One hundred and fifteen patients were included into the study group; twelve patients presented with PTX diagnosed by CT, 10 of which were detected by Pneumoscan. Thirty-six true negative results, sixty-seven false positive results, and two false negative results were obtained, which resulted in an overall sensitivity of 83.3%, specificity of 35.0% for Pneumoscan. There was no statistically significant difference between the effectiveness of Pneumoscan and CT on the detection of PTX (p=0.33). There was no difference between the size of PTX diagnosed by CT and PTX diagnosed by Pneumoscan (p=0.47). There was no statistically significant difference between Pneumoscan and CT on detecting the localisation of the PTX (p=1.00). For the 10 cases diagnosed by Pneumoscan, mean chest wall thickness was determined as 50.3 mm while mean chest wall thickness for two false negatives diagnosed by Pneumoscan was 56.5 mm. However, no statistically significant difference was found between the chest wall thickness and the effectiveness of Pneumoscan on the detection of the PTX (p=0.77). Among sixty-seven false positives diagnosed by Pneumoscan, 46.3% had additional medical signs such as bronchiectasis, pulmonary consolidation, pulmonary edema or pulmonary tumor when they had a reading with CT. The relationship between having additional medical signs at the reading with CT and the effectiveness of Pneumoscan on the detection of the PTX was investigated and no significant difference was found (p=0.472). Using Pneumoscan to detect PTX is controversial since the device has a high false positive ratio. Wherein, false positive diagnosis can cause unjustifiable chest tube insertion. In addition, the device failed to show the size of the PTX, and therefore, it did not aid in determining the treatment and prognosis on contrary to traditional diagnostic methods. The findings could not demonstrate that the device was efficient in emergency care. Further studies and increasing experience may change this outcome in upcoming years.
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Small-target leak detection for a closed vessel via infrared image sequences
NASA Astrophysics Data System (ADS)
Zhao, Ling; Yang, Hongjiu
2017-03-01
This paper focus on a leak diagnosis and localization method based on infrared image sequences. Some problems on high probability of false warning and negative affect for marginal information are solved by leak detection. An experimental model is established for leak diagnosis and localization on infrared image sequences. The differential background prediction is presented to eliminate the negative affect of marginal information on test vessel based on a kernel regression method. A pipeline filter based on layering voting is designed to reduce probability of leak point false warning. A synthesize leak diagnosis and localization algorithm is proposed based on infrared image sequences. The effectiveness and potential are shown for developed techniques through experimental results.
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[Applying competitive polymerase chain reaction to the detection of hepatitis B virus DNA].
Wang, Ling; Yang, Peng; Li, Shuang-qing; Xu, Shu-hui; Cao, Gui-qun; Zhang, Fa-qiang; Zhang, Mei-xia; Chen, Qing-ying; Xia, Qing-jie; Liu, Kai; Tang, Fang; Zhang, Yuan-zheng
2004-11-01
To reduce the rate of accidental false negative result in the HBV DNA PCR test on clinical serum samples. A competitive polymerase chain reaction (C-PCR) was used to decrease the false negative ratio. In the C-PCR, a constructed inner control DNA was added for co-amplification with the HBV target DNA. In a 20 microl C-PCR system, about 60 to 200 copies of inner control DNA could give apparent co-amplification signal band after electrophoresis on a 2% agarose gel. Five of 120 samples of clinical serum (4.2%) could not be amplified. C-PCR has the advantage of yielding information on false negative in the HBV DNA PCR assay of clinical serum samples.
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Lantieri, Francesca; Malacarne, Michela; Gimelli, Stefania; Santamaria, Giuseppe; Coviello, Domenico; Ceccherini, Isabella
2017-01-01
The presence of false positive and false negative results in the Array Comparative Genomic Hybridization (aCGH) design is poorly addressed in literature reports. We took advantage of a custom aCGH recently carried out to analyze its design performance, the use of several Agilent aberrations detection algorithms, and the presence of false results. Our study provides a confirmation that the high density design does not generate more noise than standard designs and, might reach a good resolution. We noticed a not negligible presence of false negative and false positive results in the imbalances call performed by the Agilent software. The Aberration Detection Method 2 (ADM-2) algorithm with a threshold of 6 performed quite well, and the array design proved to be reliable, provided that some additional filters are applied, such as considering only intervals with average absolute log2ratio above 0.3. We also propose an additional filter that takes into account the proportion of probes with log2ratio exceeding suggestive values for gain or loss. In addition, the quality of samples was confirmed to be a crucial parameter. Finally, this work raises the importance of evaluating the samples profiles by eye and the necessity of validating the imbalances detected. PMID:28287439
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Spatial-Spectral Approaches to Edge Detection in Hyperspectral Remote Sensing
NASA Astrophysics Data System (ADS)
Cox, Cary M.
This dissertation advances geoinformation science at the intersection of hyperspectral remote sensing and edge detection methods. A relatively new phenomenology among its remote sensing peers, hyperspectral imagery (HSI) comprises only about 7% of all remote sensing research - there are five times as many radar-focused peer reviewed journal articles than hyperspectral-focused peer reviewed journal articles. Similarly, edge detection studies comprise only about 8% of image processing research, most of which is dedicated to image processing techniques most closely associated with end results, such as image classification and feature extraction. Given the centrality of edge detection to mapping, that most important of geographic functions, improving the collective understanding of hyperspectral imagery edge detection methods constitutes a research objective aligned to the heart of geoinformation sciences. Consequently, this dissertation endeavors to narrow the HSI edge detection research gap by advancing three HSI edge detection methods designed to leverage HSI's unique chemical identification capabilities in pursuit of generating accurate, high-quality edge planes. The Di Zenzo-based gradient edge detection algorithm, an innovative version of the Resmini HySPADE edge detection algorithm and a level set-based edge detection algorithm are tested against 15 traditional and non-traditional HSI datasets spanning a range of HSI data configurations, spectral resolutions, spatial resolutions, bandpasses and applications. This study empirically measures algorithm performance against Dr. John Canny's six criteria for a good edge operator: false positives, false negatives, localization, single-point response, robustness to noise and unbroken edges. The end state is a suite of spatial-spectral edge detection algorithms that produce satisfactory edge results against a range of hyperspectral data types applicable to a diverse set of earth remote sensing applications. This work also explores the concept of an edge within hyperspectral space, the relative importance of spatial and spectral resolutions as they pertain to HSI edge detection and how effectively compressed HSI data improves edge detection results. The HSI edge detection experiments yielded valuable insights into the algorithms' strengths, weaknesses and optimal alignment to remote sensing applications. The gradient-based edge operator produced strong edge planes across a range of evaluation measures and applications, particularly with respect to false negatives, unbroken edges, urban mapping, vegetation mapping and oil spill mapping applications. False positives and uncompressed HSI data presented occasional challenges to the algorithm. The HySPADE edge operator produced satisfactory results with respect to localization, single-point response, oil spill mapping and trace chemical detection, and was challenged by false positives, declining spectral resolution and vegetation mapping applications. The level set edge detector produced high-quality edge planes for most tests and demonstrated strong performance with respect to false positives, single-point response, oil spill mapping and mineral mapping. False negatives were a regular challenge for the level set edge detection algorithm. Finally, HSI data optimized for spectral information compression and noise was shown to improve edge detection performance across all three algorithms, while the gradient-based algorithm and HySPADE demonstrated significant robustness to declining spectral and spatial resolutions.
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Abràmoff, Michael D; Niemeijer, Meindert; Suttorp-Schulten, Maria S A; Viergever, Max A; Russell, Stephen R; van Ginneken, Bram
2008-02-01
To evaluate the performance of a system for automated detection of diabetic retinopathy in digital retinal photographs, built from published algorithms, in a large, representative, screening population. We conducted a retrospective analysis of 10,000 consecutive patient visits, specifically exams (four retinal photographs, two left and two right) from 5,692 unique patients from the EyeCheck diabetic retinopathy screening project imaged with three types of cameras at 10 centers. Inclusion criteria included no previous diagnosis of diabetic retinopathy, no previous visit to ophthalmologist for dilated eye exam, and both eyes photographed. One of three retinal specialists evaluated each exam as unacceptable quality, no referable retinopathy, or referable retinopathy. We then selected exams with sufficient image quality and determined presence or absence of referable retinopathy. Outcome measures included area under the receiver operating characteristic curve (number needed to miss one case [NNM]) and type of false negative. Total area under the receiver operating characteristic curve was 0.84, and NNM was 80 at a sensitivity of 0.84 and a specificity of 0.64. At this point, 7,689 of 10,000 exams had sufficient image quality, 4,648 of 7,689 (60%) were true negatives, 59 of 7,689 (0.8%) were false negatives, 319 of 7,689 (4%) were true positives, and 2,581 of 7,689 (33%) were false positives. Twenty-seven percent of false negatives contained large hemorrhages and/or neovascularizations. Automated detection of diabetic retinopathy using published algorithms cannot yet be recommended for clinical practice. However, performance is such that evaluation on validated, publicly available datasets should be pursued. If algorithms can be improved, such a system may in the future lead to improved prevention of blindness and vision loss in patients with diabetes.
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Abad-Franch, Fernando; Valença-Barbosa, Carolina; Sarquis, Otília; Lima, Marli M.
2014-01-01
Background Vector-borne diseases are major public health concerns worldwide. For many of them, vector control is still key to primary prevention, with control actions planned and evaluated using vector occurrence records. Yet vectors can be difficult to detect, and vector occurrence indices will be biased whenever spurious detection/non-detection records arise during surveys. Here, we investigate the process of Chagas disease vector detection, assessing the performance of the surveillance method used in most control programs – active triatomine-bug searches by trained health agents. Methodology/Principal Findings Control agents conducted triplicate vector searches in 414 man-made ecotopes of two rural localities. Ecotope-specific ‘detection histories’ (vectors or their traces detected or not in each individual search) were analyzed using ordinary methods that disregard detection failures and multiple detection-state site-occupancy models that accommodate false-negative and false-positive detections. Mean (±SE) vector-search sensitivity was ∼0.283±0.057. Vector-detection odds increased as bug colonies grew denser, and were lower in houses than in most peridomestic structures, particularly woodpiles. False-positive detections (non-vector fecal streaks misidentified as signs of vector presence) occurred with probability ∼0.011±0.008. The model-averaged estimate of infestation (44.5±6.4%) was ∼2.4–3.9 times higher than naïve indices computed assuming perfect detection after single vector searches (11.4–18.8%); about 106–137 infestation foci went undetected during such standard searches. Conclusions/Significance We illustrate a relatively straightforward approach to addressing vector detection uncertainty under realistic field survey conditions. Standard vector searches had low sensitivity except in certain singular circumstances. Our findings suggest that many infestation foci may go undetected during routine surveys, especially when vector density is low. Undetected foci can cause control failures and induce bias in entomological indices; this may confound disease risk assessment and mislead program managers into flawed decision making. By helping correct bias in naïve indices, the approach we illustrate has potential to critically strengthen vector-borne disease control-surveillance systems. PMID:25233352
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Multiratio fusion change detection with adaptive thresholding
NASA Astrophysics Data System (ADS)
Hytla, Patrick C.; Balster, Eric J.; Vasquez, Juan R.; Neuroth, Robert M.
2017-04-01
A ratio-based change detection method known as multiratio fusion (MRF) is proposed and tested. The MRF framework builds on other change detection components proposed in this work: dual ratio (DR) and multiratio (MR). The DR method involves two ratios coupled with adaptive thresholds to maximize detected changes and minimize false alarms. The use of two ratios is shown to outperform the single ratio case when the means of the image pairs are not equal. MR change detection builds on the DR method by including negative imagery to produce four total ratios with adaptive thresholds. Inclusion of negative imagery is shown to improve detection sensitivity and to boost detection performance in certain target and background cases. MRF further expands this concept by fusing together the ratio outputs using a routine in which detections must be verified by two or more ratios to be classified as a true changed pixel. The proposed method is tested with synthetically generated test imagery and real datasets with results compared to other methods found in the literature. DR is shown to significantly outperform the standard single ratio method. MRF produces excellent change detection results that exhibit up to a 22% performance improvement over other methods from the literature at low false-alarm rates.
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Blanch, Jordi; Sala, Maria; Ibáñez, Josefa; Domingo, Laia; Fernandez, Belén; Otegi, Arantza; Barata, Teresa; Zubizarreta, Raquel; Ferrer, Joana; Castells, Xavier; Rué, Montserrat; Salas, Dolores
2014-01-01
Background Interval cancers are primary breast cancers diagnosed in women after a negative screening test and before the next screening invitation. Our aim was to evaluate risk factors for interval cancer and their subtypes and to compare the risk factors identified with those associated with incident screen-detected cancers. Methods We analyzed data from 645,764 women participating in the Spanish breast cancer screening program from 2000–2006 and followed-up until 2009. A total of 5,309 screen-detected and 1,653 interval cancers were diagnosed. Among the latter, 1,012 could be classified on the basis of findings in screening and diagnostic mammograms, consisting of 489 true interval cancers (48.2%), 235 false-negatives (23.2%), 172 minimal-signs (17.2%) and 114 occult tumors (11.3%). Information on the screening protocol and women's characteristics were obtained from the screening program registry. Cause-specific Cox regression models were used to estimate the hazard ratios (HR) of risks factors for interval cancer and incident screen-detected cancer. A multinomial regression model, using screen-detected tumors as a reference group, was used to assess the effect of breast density and other factors on the occurrence of interval cancer subtypes. Results A previous false-positive was the main risk factor for interval cancer (HR = 2.71, 95%CI: 2.28–3.23); this risk was higher for false-negatives (HR = 8.79, 95%CI: 6.24–12.40) than for true interval cancer (HR = 2.26, 95%CI: 1.59–3.21). A family history of breast cancer was associated with true intervals (HR = 2.11, 95%CI: 1.60–2.78), previous benign biopsy with a false-negatives (HR = 1.83, 95%CI: 1.23–2.71). High breast density was mainly associated with occult tumors (RRR = 4.92, 95%CI: 2.58–9.38), followed by true intervals (RRR = 1.67, 95%CI: 1.18–2.36) and false-negatives (RRR = 1.58, 95%CI: 1.00–2.49). Conclusion The role of women's characteristics differs among interval cancer subtypes. This information could be useful to improve effectiveness of breast cancer screening programmes and to better classify subgroups of women with different risks of developing cancer. PMID:25333936
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Role of re-screening of cervical smears in internal quality control.
Baker, A; Melcher, D; Smith, R
1995-01-01
AIMS--To investigate the use of rapid re-screening as a quality control method for previously screened cervical slides; to compare this method with 10% random re-screening and clinically indicated double screening. METHODS--Between June 1990 and December 1994, 117,890 negative smears were subjected to rapid re-screening. RESULTS--This study shows that rapid re-screening detects far greater numbers of false negative cases when compared with both 10% random re-screening and clinically indicated double screening, with no additional demand on human resources. The technique also identifies variation in the performance of screening personnel as an additional benefit. CONCLUSION--Rapid re-screening is an effective method of quality control. Although less sensitive, rapid re-screening should replace 10% random re-screening and selected re-screening as greater numbers of false negative results are detected while consuming less resources. PMID:8543619
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Detection of CIN by naked eye visualization after application of acetic acid.
Londhe, M; George, S S; Seshadri, L
1997-06-01
A prospective study was undertaken to determine the sensitivity and specificity of acetic application to the cervix followed by naked eye visualization as a screening test for detection of cervical intraepithelial neoplasia. Three hundred and seventy two sexually active woman in the reproductive age group were studied. All the women underwent Papanicolaou test, acetic acid test and colposcopy. One hundred and seventy five woman were acetic acid test negative, 197 women were acetic acid test positive. The sensitivity of acetic acid test was 72.4%, specificity 54% and false negative rate 15.2%, as compared to papanicolaou test which had a sensitivity of 13.2%, specificity of 96.3% and false negative rate of 24.4%. The advantage of the acetic acid test lies in its easy technique, low cost and high sensitivity which are important factors for determining the efficacy of any screening programme in developing countries.
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Xu, Stanley; Newcomer, Sophia; Nelson, Jennifer; Qian, Lei; McClure, David; Pan, Yi; Zeng, Chan; Glanz, Jason
2014-05-01
The Vaccine Safety Datalink project captures electronic health record data including vaccinations and medically attended adverse events on 8.8 million enrollees annually from participating managed care organizations in the United States. While the automated vaccination data are generally of high quality, a presumptive adverse event based on diagnosis codes in automated health care data may not be true (misclassification). Consequently, analyses using automated health care data can generate false positive results, where an association between the vaccine and outcome is incorrectly identified, as well as false negative findings, where a true association or signal is missed. We developed novel conditional Poisson regression models and fixed effects models that accommodate misclassification of adverse event outcome for self-controlled case series design. We conducted simulation studies to evaluate their performance in signal detection in vaccine safety hypotheses generating (screening) studies. We also reanalyzed four previously identified signals in a recent vaccine safety study using the newly proposed models. Our simulation studies demonstrated that (i) outcome misclassification resulted in both false positive and false negative signals in screening studies; (ii) the newly proposed models reduced both the rates of false positive and false negative signals. In reanalyses of four previously identified signals using the novel statistical models, the incidence rate ratio estimates and statistical significances were similar to those using conventional models and including only medical record review confirmed cases. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Moesker, F M; van Kampen, J J A; Aron, G; Schutten, M; van de Vijver, D A M C; Koopmans, M P G; Osterhaus, A D M E; Fraaij, P L A
2016-06-01
Rapid antigen detection tests (RADTs) are increasingly used to detect influenza viruses and respiratory syncytial virus (RSV). However, their sensitivity and specificity are a matter of debate, challenging their clinical usefulness. Comparing diagnostic performances of BinaxNow Influenza AB(®) (BNI) and BinaxNow RSV(®) (BNR), to those of real-time reverse transcriptase PCR (RT-PCR), virus isolation and direct immunofluorescence (D-IF) in paediatric patients. Between November 2005 and September 2013, 521 nasal washings from symptomatic children (age <5 years) attending our tertiary care centre were tested, with a combination of the respective assays using RT-PCR as gold standard. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of BNI were 69% (confidence interval [CI] [51-83]), 96% [94-97], 55% [39-70] and 98% [96-99] respectively. Of eleven false-negative samples, RT-PCR Ct-values were higher than all RT-PCR positive test results (27 vs 22, p=0.012). Of twenty false-positive samples, none were culture positive and two tested positive in D-IF. Sensitivity, specificity, PPV and NPV for BNR were 79% [73-85], 98% [96-99], 97% [93-99] and 88% [84-91]. Of the 42 false-negative samples the median Ct-value was higher than that of all RT-PCR positive samples (31 vs 23, p<0.0001). Five false-positive samples were detected. Three of these tested positive for RSV in virus isolation and D-IF. RADTs have a high specificity with BNR being superior to BNI. However, their relative low sensitivity limits their usefulness for clinical decision making in a tertiary care paediatric hospital. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.
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Argani, Pedram; Zhang, Lei; Reuter, Victor E; Tickoo, Satish K; Antonescu, Cristina R
2017-05-01
Xp11 translocation renal cell carcinoma (RCC) are defined by chromosome translocations involving the Xp11 breakpoint which results in one of a variety of TFE3 gene fusions. TFE3 break-apart florescence in situ hybridization (FISH) assays are generally preferred to TFE3 immunohistochemistry (IHC) as a means of confirming the diagnosis in archival material, as FISH is less sensitive to the variable fixation which can result in false positive or false negative IHC. Prompted by a case report in the cytogenetics literature, we identify 3 cases of Xp11 translocation RCC characterized by a subtle chromosomal inversion involving the short arm of the X chromosome, resulting in an RBM10-TFE3 gene fusion. TFE3 rearrangement was not detected by conventional TFE3 break-apart FISH, but was suggested by strong diffuse TFE3 immunoreactivity in a clean background. We then developed novel fosmid probes to detect the RBM10-TFE3 gene fusion in archival material. These cases validate RBM10-TFE3 as a recurrent gene fusion in Xp11 translocation RCC, illustrate a source of false-negative TFE3 break-apart FISH, and highlight the complementary role of TFE3 IHC and TFE3 FISH.
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Padula, Francesco; Laganà, Antonio Simone; Vitale, Salvatore Giovanni; D'Emidio, Laura; Coco, Claudio; Giannarelli, Diana; Cariola, Maria; Favilli, Alessandro; Giorlandino, Claudio
2017-05-01
Maternal age is a crucial factor in fetal aneuploidy screening, resulting in an increased rate of false-positive cases in older women and false-negative cases in younger women. The absolute risk (AR) is the simplest way to eliminate the background maternal age risk, as it represents the amount of improvement of the combined risk from the maternal background risk. The aim of this work is to assess the performance of the AR in the combined first-trimester screening for aneuploidies. A retrospective validation of the AR in the combined first-trimester screening for fetal aneuploidies, in an unselected population at Altamedica Fetal-Maternal Medical Center in Rome, between March 2007 and December 2008. Of 3845 women included in the study, we had a complete follow-up on 2984. We evaluated that an AR < 3 would individuate 22 of 23 cases of aneuploidy with a detection rate of 95.7% (95%CI 87.3-100), a false-positive rate of 8.7% (95%CI 7.7-9.7) and a false-negative rate of 4.3% (95%CI 0-12.7). In our study, the AR ameliorates the detection rate for aneuploidy. Further research and a prospective study on a larger population would help us to improve the AR in detecting most cases of aneuploidy.
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Fehr, Mathias K
2011-10-01
Sentinel lymph node (SLN) dissections have been shown to be sensitive for the evaluation of nodal basins for metastatic disease and are associated with decreased short-term and long-term morbidity when compared with complete lymph node dissection. There has been increasing interest in the use of SLN technology in gynecologic cancers. This review assesses the current evidence-based literature for the use of SLN dissections in gynecologic malignancies. Recent literature continues to support the safety and feasibility of SLN biopsy for early stage vulvar cancer with negative predictive value approaching 100 % and low false negative rates. Alternatively, for endometrial cancer most studies have reported low false-negative rates, with variable sensitivities and have reported low detection rates of the sentinel node. Studies examining the utility of SLN biopsy in early-stage cervical cancer remain promising with detection rates, sensitivities, and false-negative rates greater than 90 % for stage 1B1 tumors. SLN dissections have been shown to be effective and safe in certain, select vulvar cancer patients and can be considered an alternative surgical approach for these patients. For endometrial and cervical cancer, SLN dissection continues to have encouraging results and however needs further investigation.
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[Echocardiographic diagnosis of atrial thrombosis].
Pinto Tortolero, R; Vargas Barrón, J; Rodas, M A; Díaz de la Vega, V; Horwitz, S
1982-01-01
Seventy patients with rheumatic mitral disease were studied by M-Mode and 2D echocardiography in order to detect left atrial thrombosis before surgery. Thrombosis were suspected by the observation of abnormal echoes in the left atrium. During surgery 17 (24%) patients had atrial thrombosis. It had been suspected by echocardiography in 12 (sensitivity 70%). In 53 patients thrombosis were not found during surgery; in 46 the echo had been also negative (specificity 86%). There was a false positive detection of thrombosis by echo in 7 patients (14%) and false negativity in 5 (30%). Patients with atrial thrombosis had atrial fibrilation in 91% of cases; and the most frequent valvular disease was mitral stenosis. There was not a direct relationship among existence of left atrial thrombosis and the anteroposterior diameter of the left atrium as measured by echo. We conclude that echocardiography has good specificity to rule out atrial thrombosis and moderate sensitivity to detect it in rheumatic mitral disease.
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Bartels, Stephan; Schipper, Elisa; Hasemeier, Britta; Kreipe, Hans; Lehmann, Ulrich
2018-05-27
The detection of hotspot mutations in key cancer genes is now an essential part of the diagnostic work-up in molecular pathology. Nearly all assays for mutation detection involve an amplification step. A second single nucleotide variant (SNV) on the same allele adjacent to a mutational hotspot can interfere with primer binding, leading to unnoticed allele-specific amplification of the wild type allele and thereby false-negative mutation testing. We present two diagnostic cases with false negative sequence results for JAK2 and SRSF2. In both cases mutations would have escaped detection if only one strand of DNA had been analysed. Because many commercially available diagnostic kits rely on the analysis of only one DNA strand they are prone to fail in cases like these. Detailed protocols and quality control measures to prevent corresponding pitfalls are presented. Copyright © 2017. Published by Elsevier Inc.
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Martínez-Pacheco, María C; Ferrán de la Cierva, Luis; García-Purriños, Francisco J
Despite its importance, the existence of false negatives (patients who are told they hear well, but they have some degree of hipacusia) is rarely evaluated in programs for early detection of hearing loss. The aim of this study is to determine the variables that can lead to a delayed diagnosis, especially the existence of false negatives and the lack of registration of risk factors. A retrospective study of prevalence has been carried out, in which the medical records of children diagnosed with sensorineural hearing loss born within 2005 and 2012 in the health centers of study have been analyzed. Of the 32 children with sensorineural hearing loss, 16 passed the OAE, 12 did not passed the OAE, and in four they were not carried out. Of the children who passed the OAE, 57% have severe hearing loss. 66% of children with hearing loss presented a risk factor for hearing loss at birth, being the most frecuent family history of hearing loss, but only 7% of those with family history of hearing loss were included in the risk group. The results of the study indicate that the late diagnosis of hearing loss is related to the presence of false negatives to the OAE and the non-registration of risk factors. Copyright © 2016 Elsevier España, S.L.U. and Sociedad Española de Otorrinolaringología y Cirugía de Cabeza y Cuello. All rights reserved.
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False-positive cryptococcal antigen latex agglutination caused by disinfectants and soaps.
Blevins, L B; Fenn, J; Segal, H; Newcomb-Gayman, P; Carroll, K C
1995-01-01
Five disinfectants or soaps were tested to determine if any could be responsible for false-positive results obtained with the Latex-Crypto Antigen Detection System kit (Immuno-Mycologics, Inc., Norman, Okla.). Three disinfectants or soaps (Derma soap, 7X, and Bacdown) produced false-positive agglutination after repeated washing of ring slides during testing of a known negative cerebrospinal fluid specimen. PMID:7650214
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Edwards, Jeffrey K; Kleine, Christian; Munster, Vincent; Giuliani, Ruggero; Massaquoi, Moses; Sprecher, Armand; Chertow, Daniel S
2015-12-01
Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) is the most sensitive quantitative diagnostic assay for detection of Ebola virus in multiple body fluids. Despite the strengths of this assay, we present 2 cases of Ebola virus disease (EVD) and highlight the potential for false-negative results during the early and late stages of EVD. The first case emphasizes the low negative-predictive value of qRT-PCR during incubation and the early febrile stage of EVD, and the second case emphasizes the potential for false-negative results during recovery and late neurologic complications of EVD. Careful interpretation of test results are needed to guide difficult admission and discharge decisions in suspected or confirmed EVD.
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Piwowar-Manning, Estelle; Fogel, Jessica M.; Richardson, Paul; Wolf, Shauna; Clarke, William; Marzinke, Mark A.; Fiamma, Agnès; Donnell, Deborah; Kulich, Michal; Mbwambo, Jessie K.K.; Richter, Linda; Gray, Glenda; Sweat, Michael; Coates, Thomas J.; Eshleman, Susan H.
2015-01-01
Background Fourth-generation HIV assays detect both antigen and antibody, facilitating detection of acute/early HIV infection. The Bio-Rad GS HIV Combo Ag/Ab assay (Bio-Rad Combo) is an enzyme immunoassay that simultaneously detects HIV p24 antigen and antibodies to HIV-1 and HIV-2 in serum or plasma. Objective To evaluate the performance of the Bio-Rad Combo assay for detection of HIV infection in adults from Southern Africa. Study design Samples were obtained from adults in Soweto and Vulindlela, South Africa and Dar es Salaam, Tanzania (300 HIV-positive samples; 300 HIV-negative samples; 12 samples from individuals previously classified as having acute/early HIV infection). The samples were tested with the Bio-Rad Combo assay. Additional testing was performed to characterize the 12 acute/early samples. Results All 300 HIV-positive samples were reactive using the Bio-Rad Combo assay; false positive test results were obtained for 10 (3.3%) of the HIV-negative samples (sensitivity: 100%, 95% confidence interval [CI]: 98.8–100%); specificity: 96.7%, 95% CI: 94.0–98.4%). The assay detected 10 of the 12 infections classified as acute/early. The two infections that were not detected had viral loads < 400 copies/mL; one of those samples contained antiretroviral drugs consistent with antiretroviral therapy. Conclusions The Bio-Rad Combo assay correctly classified the majority of study specimens. The specificity reported here may be higher than that seen in other settings, since HIV-negative samples were pre-screened using a different fourth-generation test. The assay also had high sensitivity for detection of acute/early infection. False-negative test results may be obtained in individuals who are virally suppressed. PMID:25542477
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Where Have All the Interactions Gone? Estimating the Coverage of Two-Hybrid Protein Interaction Maps
Huang, Hailiang; Jedynak, Bruno M; Bader, Joel S
2007-01-01
Yeast two-hybrid screens are an important method for mapping pairwise physical interactions between proteins. The fraction of interactions detected in independent screens can be very small, and an outstanding challenge is to determine the reason for the low overlap. Low overlap can arise from either a high false-discovery rate (interaction sets have low overlap because each set is contaminated by a large number of stochastic false-positive interactions) or a high false-negative rate (interaction sets have low overlap because each misses many true interactions). We extend capture–recapture theory to provide the first unified model for false-positive and false-negative rates for two-hybrid screens. Analysis of yeast, worm, and fly data indicates that 25% to 45% of the reported interactions are likely false positives. Membrane proteins have higher false-discovery rates on average, and signal transduction proteins have lower rates. The overall false-negative rate ranges from 75% for worm to 90% for fly, which arises from a roughly 50% false-negative rate due to statistical undersampling and a 55% to 85% false-negative rate due to proteins that appear to be systematically lost from the assays. Finally, statistical model selection conclusively rejects the Erdös-Rényi network model in favor of the power law model for yeast and the truncated power law for worm and fly degree distributions. Much as genome sequencing coverage estimates were essential for planning the human genome sequencing project, the coverage estimates developed here will be valuable for guiding future proteomic screens. All software and datasets are available in Datasets S1 and S2, Figures S1–S5, and Tables S1−S6, and are also available from our Web site, http://www.baderzone.org. PMID:18039026
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A critical reappraisal of false negative sentinel lymph node biopsy in melanoma.
Manca, G; Romanini, A; Rubello, D; Mazzarri, S; Boni, G; Chiacchio, S; Tredici, M; Duce, V; Tardelli, E; Volterrani, D; Mariani, G
2014-06-01
Lymphatic mapping and sentinel lymph node biopsy (SLNB) have completely changed the clinical management of cutaneous melanoma. This procedure has been accepted worldwide as a recognized method for nodal staging. SLNB is able to accurately determine nodal basin status, providing the most useful prognostic information. However, SLNB is not a perfect diagnostic test. Several large-scale studies have reported a relatively high false-negative rate (5.6-21%), correctly defined as the proportion of false-negative results with respect to the total number of "actual" positive lymph nodes. The main purpose of this review is to address the technical issues that nuclear physicians, surgeons, and pathologists should carefully consider to improve the accuracy of SLNB by minimizing its false-negative rate. In particular, SPECT/CT imaging has demonstrated to be able to identify a greater number of sentinel lymph nodes (SLNs) than those found by planar lymphoscintigraphy. Furthermore, a unique definition in the international guidelines is missing for the operational identification of SLNs, which may be partly responsible for this relatively high false-negative rate of SLNB. Therefore, it is recommended for the scientific community to agree on the radioactive counting rate threshold so that the surgeon can be better radioguided to detect all the lymph nodes which are most likely to harbor metastases. Another possible source of error may be linked to the examination of the harvested SLNs by conventional histopathological methods. A more careful and extensive SLN analysis (e.g. molecular analysis by RT-PCR) is able to find more positive nodes, so that the false-negative rate is reduced. Older age at diagnosis, deeper lesions, histologic ulceration, head-neck anatomical location of primary lesions are the clinical factors associated with false-negative SLNBs in melanoma patients. There is still much controversy about the clinical significance of a false-negative SLNB on the prognosis of melanoma patients. Indeed, most studies have failed to show that there is worse melanoma-specific survival for false-negative compared to true-positive SLNB patients.
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Automatic mouse ultrasound detector (A-MUD): A new tool for processing rodent vocalizations.
Zala, Sarah M; Reitschmidt, Doris; Noll, Anton; Balazs, Peter; Penn, Dustin J
2017-01-01
House mice (Mus musculus) emit complex ultrasonic vocalizations (USVs) during social and sexual interactions, which have features similar to bird song (i.e., they are composed of several different types of syllables, uttered in succession over time to form a pattern of sequences). Manually processing complex vocalization data is time-consuming and potentially subjective, and therefore, we developed an algorithm that automatically detects mouse ultrasonic vocalizations (Automatic Mouse Ultrasound Detector or A-MUD). A-MUD is a script that runs on STx acoustic software (S_TOOLS-STx version 4.2.2), which is free for scientific use. This algorithm improved the efficiency of processing USV files, as it was 4-12 times faster than manual segmentation, depending upon the size of the file. We evaluated A-MUD error rates using manually segmented sound files as a 'gold standard' reference, and compared them to a commercially available program. A-MUD had lower error rates than the commercial software, as it detected significantly more correct positives, and fewer false positives and false negatives. The errors generated by A-MUD were mainly false negatives, rather than false positives. This study is the first to systematically compare error rates for automatic ultrasonic vocalization detection methods, and A-MUD and subsequent versions will be made available for the scientific community.
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The efficacy of sentinel lymph node mapping with indocyanine green in cervical cancer.
Kim, Ju-Hyun; Kim, Dae-Yeon; Suh, Dae-Shik; Kim, Jong-Hyeok; Kim, Yong-Man; Kim, Young-Tak; Nam, Joo-Hyun
2018-03-09
Lymph node metastasis is a significant predictive factor for disease recurrence and survival in cervical cancer patients. Given the importance of lymph node metastasis, it is imperative that patients harboring metastasis are identified and can undergo appropriate treatment. Sentinel lymph node (SLN) mapping has drawn attention as a lymph node mapping technique. We evaluated the feasibility and efficacy of (SLN) mapping using indocyanine green (ICG) in cervical cancer. We performed a single-center, retrospective study of 103 surgically treated cervical cancer patients who underwent SLN mapping. After using ICG to detect SLN during surgery, we removed the SLNs followed by laparoscopic or robotic-assisted radical surgery and bilateral pelvic lymphadenectomy. Stage IB1 was the most common (61.17%). At least one SLN was detected in all cases. Eighty-eight patients (85.44%) had bilateral pelvic SLNs. The mean number of SLN per patient was 2.34. The side-specific sensitivity was 71.43%, the specificity was 100%, the negative predictive value (NPV) was 93.98%, and the false negative rate (FNR) was 28.57%. In cases of tumors smaller than 2 cm with negative lymph node metastasis on imaging, the study revealed a side-specific sensitivity of 100%, a specificity of 100%, a NPV of 100%, and a FNR of 0%. Large tumor size (≥ 4 cm), a previous history of a loop electrosurgical excision procedure (LEEP), depth of invasion (≥ 50%), the microscopic parametrial (PM) invasion, and vaginal extension were significantly associated with the false-negative detection of SLN. Moreover, the microscopic PM invasion was the only risk factor of the false-negative detection of SLN in multivariate analysis. SLN mapping with ICG in cervical cancer is feasible and has high detection rate. The sensitivity of 100% was high enough to perform SLN biopsy alone in an early stage in which the tumor is less than 2 cm, with no lymphadenopathy on image examination. However, for large or invasive tumors, we would have to be cautious about performing SLN biopsy alone. Retrospectively registered 2017-0600.
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ClubSub-P: Cluster-Based Subcellular Localization Prediction for Gram-Negative Bacteria and Archaea
Paramasivam, Nagarajan; Linke, Dirk
2011-01-01
The subcellular localization (SCL) of proteins provides important clues to their function in a cell. In our efforts to predict useful vaccine targets against Gram-negative bacteria, we noticed that misannotated start codons frequently lead to wrongly assigned SCLs. This and other problems in SCL prediction, such as the relatively high false-positive and false-negative rates of some tools, can be avoided by applying multiple prediction tools to groups of homologous proteins. Here we present ClubSub-P, an online database that combines existing SCL prediction tools into a consensus pipeline from more than 600 proteomes of fully sequenced microorganisms. On top of the consensus prediction at the level of single sequences, the tool uses clusters of homologous proteins from Gram-negative bacteria and from Archaea to eliminate false-positive and false-negative predictions. ClubSub-P can assign the SCL of proteins from Gram-negative bacteria and Archaea with high precision. The database is searchable, and can easily be expanded using either new bacterial genomes or new prediction tools as they become available. This will further improve the performance of the SCL prediction, as well as the detection of misannotated start codons and other annotation errors. ClubSub-P is available online at http://toolkit.tuebingen.mpg.de/clubsubp/ PMID:22073040
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A Region Tracking-Based Vehicle Detection Algorithm in Nighttime Traffic Scenes
Wang, Jianqiang; Sun, Xiaoyan; Guo, Junbin
2013-01-01
The preceding vehicles detection technique in nighttime traffic scenes is an important part of the advanced driver assistance system (ADAS). This paper proposes a region tracking-based vehicle detection algorithm via the image processing technique. First, the brightness of the taillights during nighttime is used as the typical feature, and we use the existing global detection algorithm to detect and pair the taillights. When the vehicle is detected, a time series analysis model is introduced to predict vehicle positions and the possible region (PR) of the vehicle in the next frame. Then, the vehicle is only detected in the PR. This could reduce the detection time and avoid the false pairing between the bright spots in the PR and the bright spots out of the PR. Additionally, we present a thresholds updating method to make the thresholds adaptive. Finally, experimental studies are provided to demonstrate the application and substantiate the superiority of the proposed algorithm. The results show that the proposed algorithm can simultaneously reduce both the false negative detection rate and the false positive detection rate.
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False Positive and False Negative Effects on Network Attacks
NASA Astrophysics Data System (ADS)
Shang, Yilun
2018-01-01
Robustness against attacks serves as evidence for complex network structures and failure mechanisms that lie behind them. Most often, due to detection capability limitation or good disguises, attacks on networks are subject to false positives and false negatives, meaning that functional nodes may be falsely regarded as compromised by the attacker and vice versa. In this work, we initiate a study of false positive/negative effects on network robustness against three fundamental types of attack strategies, namely, random attacks (RA), localized attacks (LA), and targeted attack (TA). By developing a general mathematical framework based upon the percolation model, we investigate analytically and by numerical simulations of attack robustness with false positive/negative rate (FPR/FNR) on three benchmark models including Erdős-Rényi (ER) networks, random regular (RR) networks, and scale-free (SF) networks. We show that ER networks are equivalently robust against RA and LA only when FPR equals zero or the initial network is intact. We find several interesting crossovers in RR and SF networks when FPR is taken into consideration. By defining the cost of attack, we observe diminishing marginal attack efficiency for RA, LA, and TA. Our finding highlights the potential risk of underestimating or ignoring FPR in understanding attack robustness. The results may provide insights into ways of enhancing robustness of network architecture and improve the level of protection of critical infrastructures.
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Ability of Ultrasonography in Detection of Different Extremity Bone Fractures; a Case Series Study
Bozorgi, Farzad; Shayesteh Azar, Massoud; Montazer, Seyed Hossein; Chabra, Aroona; Heidari, Seyed Farshad; Khalilian, Alireza
2017-01-01
Introduction: Despite radiography being the gold standard in evaluation of orthopedic injuries, using bedside ultrasonography has several potential supremacies such as avoiding exposure to ionizing radiation, availability in pre-hospital settings, being extensively accessible, and ability to be used on the bedside. The aim of the present study is to evaluate the diagnostic accuracy of ultrasonography in detection of extremity bone fractures. Methods: This study is a case series study, which was prospectively conducted on multiple blunt trauma patients, who were 18 years old or older, had stable hemodynamic, Glasgow coma scale 15, and signs or symptoms of a possible extremity bone fracture. After initial assessment, ultrasonography of suspected bones was performed by a trained emergency medicine resident and prevalence of true positive and false negative findings were calculated compared to plain radiology. Results: 108 patients with the mean age of 44.6 ± 20.4 years were studied (67.6% male). Analysis was done on 158 sites of fracture, which were confirmed with plain radiography. 91 (57.6%) cases were suspected to have upper extremity fracture(s) and 67 (42.4%) to have lower ones. The most frequent site of injuries were forearm (36.7%) in upper limbs and leg (27.8%) in lower limbs. Prevalence of true positive and false negative cases for fractures detected by ultrasonography were 59 (64.8%) and 32 (35.52%) for upper and 49 (73.1%) and 18 (26.9%) for lower extremities, respectively. In addition, prevalence of true positive and false negative detected cases for intra-articular fractures were 24 (48%) and 26 (52%), respectively. Conclusion The present study shows the moderate sensitivity (68.3%) of ultrasonography in detection of different extremity bone fractures. Ultrasonography showed the best sensitivity in detection of femur (100%) and humerus (76.2%) fractures, respectively. It had low sensitivity in detection of in intra-articular fractures. PMID:28286822
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Ability of Ultrasonography in Detection of Different Extremity Bone Fractures; a Case Series Study.
Bozorgi, Farzad; Shayesteh Azar, Massoud; Montazer, Seyed Hossein; Chabra, Aroona; Heidari, Seyed Farshad; Khalilian, Alireza
2017-01-01
Despite radiography being the gold standard in evaluation of orthopedic injuries, using bedside ultrasonography has several potential supremacies such as avoiding exposure to ionizing radiation, availability in pre-hospital settings, being extensively accessible, and ability to be used on the bedside. The aim of the present study is to evaluate the diagnostic accuracy of ultrasonography in detection of extremity bone fractures. This study is a case series study, which was prospectively conducted on multiple blunt trauma patients, who were 18 years old or older, had stable hemodynamic, Glasgow coma scale 15, and signs or symptoms of a possible extremity bone fracture. After initial assessment, ultrasonography of suspected bones was performed by a trained emergency medicine resident and prevalence of true positive and false negative findings were calculated compared to plain radiology. 108 patients with the mean age of 44.6 ± 20.4 years were studied (67.6% male). Analysis was done on 158 sites of fracture, which were confirmed with plain radiography. 91 (57.6%) cases were suspected to have upper extremity fracture(s) and 67 (42.4%) to have lower ones. The most frequent site of injuries were forearm (36.7%) in upper limbs and leg (27.8%) in lower limbs. Prevalence of true positive and false negative cases for fractures detected by ultrasonography were 59 (64.8%) and 32 (35.52%) for upper and 49 (73.1%) and 18 (26.9%) for lower extremities, respectively. In addition, prevalence of true positive and false negative detected cases for intra-articular fractures were 24 (48%) and 26 (52%), respectively. The present study shows the moderate sensitivity (68.3%) of ultrasonography in detection of different extremity bone fractures. Ultrasonography showed the best sensitivity in detection of femur (100%) and humerus (76.2%) fractures, respectively. It had low sensitivity in detection of in intra-articular fractures.
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Xie, Gui-lin; Yin, Jun-xia; Duan, Xin-yu; Feng, Xiao-hui; Wang, Yang; Jiang, Kai; Chen, Xin-mei
2015-06-01
One hundred and fifty-nine serum samples from hydatid disease patients and 80 serum samples from patients with other liver diseases were detected by gold-immunochromatographic assay, and read by naked eyes and the gold-immunochromatographic test strip reader. The sensitivity, specificity, and accuracy of eye-based method was 92.4% (147/159), 85.0% (68/80), and 89.9% (215/239), which was lower than that of the reader detection (95.6%, 93.7%, 95.0%, respectively). While, its false negative rate (7.5%, 12/159) and false positive rate (15.0%, 12/80) was higher than that of the reader detection (4.4% and 6.3%, respectively).
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Navabi, Nazlee; Montebatsi, Milton; Scott, Michelle; Gluckman, Stephen J; Reid, Michael J A
2015-01-01
A case of false-negative serum latex agglutination cryptococcal antigen (CRAG) test in a 45-year-old HIV-positive male with Cryptococcus-positive culture is described. The patient was presented to a hospital in Botswana, with breathlessness and a diffuse papular rash. His CD4 count was 25 cells/μL. Despite the suspicion for disseminated cryptococcal disease, an initial serum CRAG latex test was negative. Results of subsequent Indian ink staining, culture of cerebrospinal fluid and skin scrapings, and serum lateral flow immunoassay (LFA) were all positive for Cryptococcus neoformans. There are several possible explanations for the false-negative CRAG latex test. Given the positive LFA result, we speculate that disease may have been caused by Cryptococcus gattii, which is estimated to be responsible for between 15% and 30% of all cryptococcal diseases in Botswana. Reduced sensitivity of CRAG latex assays for detecting C gattii may lead to underdiagnosis of cryptococcal infection. © The Author(s) 2014.
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Sentinel lymph node mapping in melanoma: the issue of false-negative findings.
Manca, Gianpiero; Rubello, Domenico; Romanini, Antonella; Boni, Giuseppe; Chiacchio, Serena; Tredici, Manuel; Mazzarri, Sara; Duce, Valerio; Colletti, Patrick M; Volterrani, Duccio; Mariani, Giuliano
2014-07-01
Management of cutaneous melanoma has changed after introduction in the clinical routine of sentinel lymph node biopsy (SLNB) for nodal staging. By defining the nodal basin status, SLNB provides a powerful prognostic information. Nevertheless, some debate still surrounds the accuracy of this procedure in terms of false-negative rate. Several large-scale studies have reported a relatively high false-negative rate (5.6%-21%), correctly defined as the proportion of false-negative results with respect to the total number of "actual" positive lymph nodes. In this review, we identified all the technical aspects that the nuclear medicine physician, the surgeon, and the pathologist should take into account to improve accuracy of the procedure and minimize the false-negative rate. In particular, SPECT/CT imaging detects more SLNs than those found by planar lymphoscintigraphy. Furthermore, the nuclear medicine community should reach a consensus on the radioactive counting rate threshold to better guide the surgeon in identifying the lymph nodes with the highest likelihood of housing metastases ("true biologic SLNs"). Analysis of the harvested SLNs by conventional techniques is also a further potential source for error. More accurate SLN analysis (eg, molecular analysis by reverse transcriptase-polymerase chain reaction) and more extensive SLN sampling identify more positive nodes, thus reducing the false-negative rate.The clinical factors identifying patients at higher-risk local recurrence after a negative SLNB include older age at diagnosis, deeper lesions, histological ulceration, and head-neck anatomic location of the primary lesion.The clinical impact of a false-negative SLNB on the prognosis of melanoma patients remains controversial, because the majority of studies have failed to demonstrate overall statistically significant disadvantage in melanoma-specific survival for false-negative SLNB patients compared with true-positive SLNB patients.When new more effective drugs will be available in the adjuvant setting for stage III melanoma patients, the implication of an accurate staging procedure for the sentinel lymph nodes will be crucial for both patients and clinicians. Standardization and accuracy of SLN identification, removal, and analysis are required.
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Herbert, Cornelia; Kübler, Andrea
2011-01-01
The present study investigated event-related brain potentials elicited by true and false negated statements to evaluate if discrimination of the truth value of negated information relies on conscious processing and requires higher-order cognitive processing in healthy subjects across different levels of stimulus complexity. The stimulus material consisted of true and false negated sentences (sentence level) and prime-target expressions (word level). Stimuli were presented acoustically and no overt behavioral response of the participants was required. Event-related brain potentials to target words preceded by true and false negated expressions were analyzed both within group and at the single subject level. Across the different processing conditions (word pairs and sentences), target words elicited a frontal negativity and a late positivity in the time window from 600-1000 msec post target word onset. Amplitudes of both brain potentials varied as a function of the truth value of the negated expressions. Results were confirmed at the single-subject level. In sum, our results support recent suggestions according to which evaluation of the truth value of a negated expression is a time- and cognitively demanding process that cannot be solved automatically, and thus requires conscious processing. Our paradigm provides insight into higher-order processing related to language comprehension and reasoning in healthy subjects. Future studies are needed to evaluate if our paradigm also proves sensitive for the detection of consciousness in non-responsive patients.
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Assessing conservation lands for forest birds in an exurban landscape
Paige F.B. Ferguson; Michael J. Conroy; Jeffrey Hepinstall-Cymerman
2017-01-01
Exurban development is the fastest growing type of land use in the United States and is prominent in the southern Appalachian region. A potential consequence of exurban development is the loss and fragmentation of wildlife habitat. We used a Bayesian model that accounts for false positive and false negative detections to make inferences about how the occupancy...
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Smith, M A; Dyson, S J; Murray, R C
2012-11-01
To determine the reliability of 2 magnetic resonance imaging (MRI) systems for detection of cartilage and bone lesions of the equine fetlock. To test the hypotheses that lesions in cartilage, subchondral and trabecular bone of the equine fetlock verified using histopathology can be detected on high- and low-field MR images with a low incidence of false positive or negative results; that low-field images are less reliable than high-field images for detection of cartilage lesions; and that combining results of interpretation from different pulse sequences increases detection of cartilage lesions. High- and low-field MRI was performed on 19 limbs from horses identified with fetlock lameness prior to euthanasia. Grading systems were used to score cartilage, subchondral and trabecular bone on MR images and histopathology. Sensitivity and specificity were calculated for images. High-field T2*-weighted gradient echo (T2*W-GRE) and low-field T2-weighted fast spin echo (T2W-FSE) images had high sensitivity but low specificity for detection of cartilage lesions. All pulse sequences had high sensitivity and low-moderate specificity for detection of subchondral bone lesions and moderate sensitivity and moderate-high specificity for detection of trabecular bone lesions (histopathology as gold standard). For detection of lesions of trabecular bone low-field T2*W-GRE images had higher sensitivity and specificity than T2W-FSE images. There is high likelihood of false positive results using high- or low-field MRI for detection of cartilage lesions and moderate-high likelihood of false positive results for detection of subchondral bone lesions compared with histopathology. Combining results of interpretation from different pulse sequences did not increase detection of cartilage lesions. MRI interpretation of trabecular bone was more reliable than cartilage or subchondral bone in both MR systems. Independent interpretation of a variety of pulse sequences may maximise detection of cartilage and bone lesions in the fetlock. Clinicians should be aware of potential false positive and negative results. © 2012 EVJ Ltd.
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Petrillo, Antonella; Fusco, Roberta; Petrillo, Mario; Triunfo, Flavia; Filice, Salvatore; Vallone, Paolo; Setola, Sergio Venanzio; Rubulotta, Mariarosaria; Di Bonito, Maurizio; Rinaldo, Massimo; D'Aiuto, Massimiliano; Brunetti, Arturo
2017-06-01
The purpose of this study was to evaluate the added value of breast magnetic resonance imaging (MRI) in preoperative diagnosis of ductal carcinoma in situ (DCIS). We reviewed our institution database of 3499 consecutive patients treated for breast cancer. A total of 362 patients with histologically proven DCIS were selected from the institutional database. Of these, 245 (67.7%) preoperatively underwent conventional imaging (CI) (mammography/ultrasonography) (CI group), and 117 (32.3%) underwent CI and dynamic MRI (CI + MRI group). The pathology of surgical specimens served as a reference standard. The Mann-Whitney U, χ 2 test, and Spearman correlation coefficient were performed. The CI + MRI group showed a sensitivity of 98.5% with an increase of 10.1% compared with the CI group to detect pure DCIS. Dynamic MRI identified 19.7% (n = 13) additional pure DCIS compared with CI. In the CI + MRI group, a single (1.5%) false negative was reported, whereas in the CI group, 11 (11.6%) false negatives were reported. Moreover, the CI + MRI group showed a sensitivity of 98.0% to detect DCIS + small invasive component. In this group, dynamic MRI identified 21.6% (n = 11) additional DCIS and a single (2.0%) false negative compared with the CI group, whereas in the CI group, 7 (4.7%) false negatives were reported. MRI and histopathologically measured lesion sizes, Breast Imaging Reporting and Data System MRI assessment categories, and enhancement signal intensity curve types showed a significant correlation. The MRI detection rate of DCIS increased significantly with increasing nuclear grade. Preoperative breast MRI showed a better accuracy then CI in preoperative diagnosis for both pure DCIS and DCIS + small invasive component with a precise assessment of lesion size. This can provide a more appropriate management of DCIS patients. Copyright © 2016 Elsevier Inc. All rights reserved.
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Chakravorty, Soumitesh; Simmons, Ann Marie; Rowneki, Mazhgan; Parmar, Heta; Cao, Yuan; Ryan, Jamie; Banada, Padmapriya P; Deshpande, Srinidhi; Shenai, Shubhada; Gall, Alexander; Glass, Jennifer; Krieswirth, Barry; Schumacher, Samuel G; Nabeta, Pamela; Tukvadze, Nestani; Rodrigues, Camilla; Skrahina, Alena; Tagliani, Elisa; Cirillo, Daniela M; Davidow, Amy; Denkinger, Claudia M; Persing, David; Kwiatkowski, Robert; Jones, Martin; Alland, David
2017-08-29
The Xpert MTB/RIF assay (Xpert) is a rapid test for tuberculosis (TB) and rifampin resistance (RIF-R) suitable for point-of-care testing. However, it has decreased sensitivity in smear-negative sputum, and false identification of RIF-R occasionally occurs. We developed the Xpert MTB/RIF Ultra assay (Ultra) to improve performance. Ultra and Xpert limits of detection (LOD), dynamic ranges, and RIF-R rpoB mutation detection were tested on Mycobacterium tuberculosis DNA or sputum samples spiked with known numbers of M. tuberculosis H37Rv or Mycobacterium bovis BCG CFU. Frozen and prospectively collected clinical samples from patients suspected of having TB, with and without culture-confirmed TB, were also tested. For M. tuberculosis H37Rv, the LOD was 15.6 CFU/ml of sputum for Ultra versus 112.6 CFU/ml of sputum for Xpert, and for M. bovis BCG, it was 143.4 CFU/ml of sputum for Ultra versus 344 CFU/ml of sputum for Xpert. Ultra resulted in no false-positive RIF-R specimens, while Xpert resulted in two false-positive RIF-R specimens. All RIF-R-associated M. tuberculosis rpoB mutations tested were identified by Ultra. Testing on clinical sputum samples, Ultra versus Xpert, resulted in an overall sensitivity of 87.5% (95% confidence interval [CI], 82.1, 91.7) versus 81.0% (95% CI, 74.9, 86.2) and a sensitivity on sputum smear-negative samples of 78.9% (95% CI, 70.0, 86.1) versus 66.1% (95% CI, 56.4, 74.9). Both tests had a specificity of 98.7% (95% CI, 93.0, 100), and both had comparable accuracies for detection of RIF-R in these samples. Ultra should significantly improve TB detection, especially in patients with paucibacillary disease, and may provide more-reliable RIF-R detection. IMPORTANCE The Xpert MTB/RIF assay (Xpert), the first point-of-care assay for tuberculosis (TB), was endorsed by the World Health Organization in December 2010. Since then, 23 million Xpert tests have been procured in 130 countries. Although Xpert showed high overall sensitivity and specificity with pulmonary samples, its sensitivity has been lower with smear-negative pulmonary samples and extrapulmonary samples. In addition, the prediction of rifampin resistance (RIF-R) in paucibacillary samples and for a few rpoB mutations has resulted in both false-positive and false-negative results. The present study is the first demonstration of the design features and operational characteristics of an improved Xpert Ultra assay. This study also shows that the Ultra format overcomes many of the known shortcomings of Xpert. The new assay should significantly improve TB detection, especially in patients with paucibacillary disease, and provide more-reliable detection of RIF-R. Copyright © 2017 Chakravorty et al.
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Zheng, Shu-Guang; Xu, Hui-Xiong; Lu, Ming-De; Xie, Xiao-Yan; Xu, Zuo-Feng; Liu, Guang-Jian; Liu, Lin-Na
2013-01-01
AIM: To assess the usefulness of contrast-enhanced ultrasound (CEUS) during follow-up after percutaneous ablation therapy for hepatocellular carcinoma (HCC). METHODS: A total of 141 patients with HCCs who received percutaneous ablation therapy were assessed by paired follow-up CEUS and contrast-enhanced computed tomography (CECT). The follow-up scheme was designed prospectively and the intervals between CEUS and CECT examinations were less than 14 d. Both images of follow-up CEUS and CECT were reviewed by radiologists. The ablated lesions were evaluated and classified as local tumor progression (LTP) and LTP-free. LTP was defined as regrowth of tumor inside or adjacent to the successfully treated nodule. The detected new intrahepatic recurrences were also evaluated and defined as presence of intrahepatic new foci. On CEUS and CECT, LTP and new intrahepatic recurrence both were displayed as typical enhancement pattern of HCC (i.e., hyper-enhancing during the arterial phase and washout in the late phase). With CECT as the reference standard, the ability of CEUS in detecting LTP or new intrahepatic recurrence during follow-up was evaluated. RESULTS: During a follow-up period of 1-31 mo (median, 4 mo), 169 paired CEUS and CECT examinations were carried out for the 141 patients. For a total of 221 ablated lesions, 266 comparisons between CEUS and CECT findings were performed. Thirty-three LTPs were detected on CEUS whereas 40 LTPs were detected on CECT, there was significant difference (P < 0.001). In comparison with CECT, the numbers of false positive and false negative LTPs detected on CEUS were 6 and 13, respectively; the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and overall accuracy of CEUS in detecting LTPs were 67.5%, 97.4%, 81.8%, 94.4% and 92.3%, respectively. Meanwhile, 131 new intrahepatic recurrent foci were detected on CEUS whereas 183 were detected on CECT, there was also significant difference (P < 0.05). In comparison with CECT, the numbers of false positive and false negative intrahepatic recurrences detected on CEUS were 13 and 65, respectively; the sensitivity, specificity, PPV, NPV and overall accuracy of CEUS in detecting new intrahepatic recurrent foci were 77.7%, 92.0%, 92.4%, 76.7% and 84.0%, respectively. CONCLUSION: The sensitivity of CEUS in detecting LTP and new intrahepatic recurrence after percutaneous ablation therapy is relatively low in comparison with CECT. PMID:23430451
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Miller, David A W; Nichols, James D; Gude, Justin A; Rich, Lindsey N; Podruzny, Kevin M; Hines, James E; Mitchell, Michael S
2013-01-01
Large-scale presence-absence monitoring programs have great promise for many conservation applications. Their value can be limited by potential incorrect inferences owing to observational errors, especially when data are collected by the public. To combat this, previous analytical methods have focused on addressing non-detection from public survey data. Misclassification errors have received less attention but are also likely to be a common component of public surveys, as well as many other data types. We derive estimators for dynamic occupancy parameters (extinction and colonization), focusing on the case where certainty can be assumed for a subset of detections. We demonstrate how to simultaneously account for non-detection (false negatives) and misclassification (false positives) when estimating occurrence parameters for gray wolves in northern Montana from 2007-2010. Our primary data source for the analysis was observations by deer and elk hunters, reported as part of the state's annual hunter survey. This data was supplemented with data from known locations of radio-collared wolves. We found that occupancy was relatively stable during the years of the study and wolves were largely restricted to the highest quality habitats in the study area. Transitions in the occupancy status of sites were rare, as occupied sites almost always remained occupied and unoccupied sites remained unoccupied. Failing to account for false positives led to over estimation of both the area inhabited by wolves and the frequency of turnover. The ability to properly account for both false negatives and false positives is an important step to improve inferences for conservation from large-scale public surveys. The approach we propose will improve our understanding of the status of wolf populations and is relevant to many other data types where false positives are a component of observations.
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Evaluation of musculoskeletal sepsis with indium-111 white blood cell imaging
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ouzounian, T.J.; Thompson, L.; Grogan, T.J.
The detection of musculoskeletal sepsis, especially following joint replacement, continues to be a challenging problem. Often, even with invasive diagnostic evaluation, the diagnosis of infection remains uncertain. This is a report on the first 55 Indium-111 white blood cell (WBC) images performed in 39 patients for the evaluation of musculoskeletal sepsis. There were 40 negative and 15 positive Indium-111 WBC images. These were correlated with operative culture and tissue pathology, aspiration culture, and clinical findings. Thirty-eight images were performed for the evaluation of possible total joint sepsis (8 positive and 30 negative images); 17 for the evaluation of nonarthroplasty-related musculoskeletalmore » sepsis (7 positive and 10 negative images). Overall, there were 13 true-positive, 39 true-negative, two false-positive, and one false-negative images. Indium-111 WBC imaging is a sensitive and specific means of evaluating musculoskeletal sepsis, especially following total joint replacement.« less
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Parshionikar, Sandhya U; Cashdollar, Jennifer; Fout, G Shay
2004-10-01
Enteric viruses often contaminate water sources causing frequent outbreaks of gastroenteritis. Reverse transcription-polymerase chain reaction (RT-PCR) assays are commonly used for detection of human enteric viruses in environmental and drinking water samples. RT-PCR provides a means to rapidly detect low levels of these viruses, but it is sensitive to inhibitors that are present in water samples. Inhibitors of RT-PCR are concentrated along with viruses during sample processing. While procedures have been developed to remove inhibitors, none of them completely remove all inhibitors from all types of water matrices. This problem requires that adequate controls be used to distinguish true from potentially false-negative results. To address this problem, we have developed homologous viral internal controls for hepatitis A virus (HAV), poliovirus, Norwalk virus and rotavirus. These internal controls can be used in RT-PCR assays for the detection of the above viruses by competitive amplification, thereby allowing the detection of false negatives in processed water samples. The internal controls developed in this study were successfully tested with virus-seeded environmental water sample concentrates.
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[Exclusive use of blue dye to detect sentinel lymph nodes in breast cancer].
Bühler H, Simón; Rojas P, Hugo; Cayazzo M, Daniela; Cunill C, Eduardo; Vesperinas A, Gonzalo; Hamilton S, James
2008-08-01
The use of a dye and radiocolloid to detect sentinel lymph nodes in breast cancer increases the detection rates. However the use of either method alone does not modify the false negative rate. Therefore there is no formal contraindication for the exclusive use of dye to detect nodes. To report a prospective analysis of the exclusive blue dye technique for sentinel node biopsy in patients with early breast cancer. We analyzed the first 100 women with pathologically proven breast cancer who met the inclusion criteria. Patent blue dye was used as colorant. In the first 25 cases sentinel node was identified using radiocolloid and blue dye an then an axillary dissection performed. In the next 25 women, blue dye was used exclusively for detection and an axillary dissection was performed. In the next 50 cases, blue dye was used and only isolated sentinel node biopsy was performed. In 92 of the 100 women a sentinel node was successfully detected. In the first 50 women, the false negative rate of sentinel lymph node detection was 6.9%. No complications occurred. During follow-up, lasting three to 29 months, no axillary relapse was observed. Sentinel node biopsy in patients with early breast cancer using exclusively blue dye is feasible and safe.
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Evaluation of the LDBIO point of care test for the combined detection of toxoplasmic IgG and IgM.
Chapey, Emmanuelle; Wallon, Martine; Peyron, François
2017-01-01
The toxoplasma ICT IgG-IgM rapid diagnostic test for the simultaneous detection of specific toxoplasmic immunoglobulin (Ig) G and IgM was compared with the Architect fully automated chemiluminescence test. Four hundred sera were included, among which 248 scored negative in Architect. The cassettes were easily read with the naked eye. Diagnostic sensitivity and specificity were 97% and 96%, respectively. The test scored 8 false-positive IgG and yielded negative results in 3 sera displaying unspecific IgM in Architect. The LDBIO appears to be a reliable first line test, although the false-positive results for IgG deserve further investigation. Such an easily performed test could be used advantageously for screening for toxoplasmosis in pregnant women. Copyright © 2016 Elsevier B.V. All rights reserved.
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Wu, Zhijin; Liu, Dongmei; Sui, Yunxia
2008-02-01
The process of identifying active targets (hits) in high-throughput screening (HTS) usually involves 2 steps: first, removing or adjusting for systematic variation in the measurement process so that extreme values represent strong biological activity instead of systematic biases such as plate effect or edge effect and, second, choosing a meaningful cutoff on the calculated statistic to declare positive compounds. Both false-positive and false-negative errors are inevitable in this process. Common control or estimation of error rates is often based on an assumption of normal distribution of the noise. The error rates in hit detection, especially false-negative rates, are hard to verify because in most assays, only compounds selected in primary screening are followed up in confirmation experiments. In this article, the authors take advantage of a quantitative HTS experiment in which all compounds are tested 42 times over a wide range of 14 concentrations so true positives can be found through a dose-response curve. Using the activity status defined by dose curve, the authors analyzed the effect of various data-processing procedures on the sensitivity and specificity of hit detection, the control of error rate, and hit confirmation. A new summary score is proposed and demonstrated to perform well in hit detection and useful in confirmation rate estimation. In general, adjusting for positional effects is beneficial, but a robust test can prevent overadjustment. Error rates estimated based on normal assumption do not agree with actual error rates, for the tails of noise distribution deviate from normal distribution. However, false discovery rate based on empirically estimated null distribution is very close to observed false discovery proportion.
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Automatic mouse ultrasound detector (A-MUD): A new tool for processing rodent vocalizations
Reitschmidt, Doris; Noll, Anton; Balazs, Peter; Penn, Dustin J.
2017-01-01
House mice (Mus musculus) emit complex ultrasonic vocalizations (USVs) during social and sexual interactions, which have features similar to bird song (i.e., they are composed of several different types of syllables, uttered in succession over time to form a pattern of sequences). Manually processing complex vocalization data is time-consuming and potentially subjective, and therefore, we developed an algorithm that automatically detects mouse ultrasonic vocalizations (Automatic Mouse Ultrasound Detector or A-MUD). A-MUD is a script that runs on STx acoustic software (S_TOOLS-STx version 4.2.2), which is free for scientific use. This algorithm improved the efficiency of processing USV files, as it was 4–12 times faster than manual segmentation, depending upon the size of the file. We evaluated A-MUD error rates using manually segmented sound files as a ‘gold standard’ reference, and compared them to a commercially available program. A-MUD had lower error rates than the commercial software, as it detected significantly more correct positives, and fewer false positives and false negatives. The errors generated by A-MUD were mainly false negatives, rather than false positives. This study is the first to systematically compare error rates for automatic ultrasonic vocalization detection methods, and A-MUD and subsequent versions will be made available for the scientific community. PMID:28727808
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Ruiz-Gutierrez, Viviana; Hooten, Melvin B.; Campbell Grant, Evan H.
2016-01-01
Biological monitoring programmes are increasingly relying upon large volumes of citizen-science data to improve the scope and spatial coverage of information, challenging the scientific community to develop design and model-based approaches to improve inference.Recent statistical models in ecology have been developed to accommodate false-negative errors, although current work points to false-positive errors as equally important sources of bias. This is of particular concern for the success of any monitoring programme given that rates as small as 3% could lead to the overestimation of the occurrence of rare events by as much as 50%, and even small false-positive rates can severely bias estimates of occurrence dynamics.We present an integrated, computationally efficient Bayesian hierarchical model to correct for false-positive and false-negative errors in detection/non-detection data. Our model combines independent, auxiliary data sources with field observations to improve the estimation of false-positive rates, when a subset of field observations cannot be validated a posteriori or assumed as perfect. We evaluated the performance of the model across a range of occurrence rates, false-positive and false-negative errors, and quantity of auxiliary data.The model performed well under all simulated scenarios, and we were able to identify critical auxiliary data characteristics which resulted in improved inference. We applied our false-positive model to a large-scale, citizen-science monitoring programme for anurans in the north-eastern United States, using auxiliary data from an experiment designed to estimate false-positive error rates. Not correcting for false-positive rates resulted in biased estimates of occupancy in 4 of the 10 anuran species we analysed, leading to an overestimation of the average number of occupied survey routes by as much as 70%.The framework we present for data collection and analysis is able to efficiently provide reliable inference for occurrence patterns using data from a citizen-science monitoring programme. However, our approach is applicable to data generated by any type of research and monitoring programme, independent of skill level or scale, when effort is placed on obtaining auxiliary information on false-positive rates.
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Statistical behavior of ten million experimental detection limits
NASA Astrophysics Data System (ADS)
Voigtman, Edward; Abraham, Kevin T.
2011-02-01
Using a lab-constructed laser-excited fluorimeter, together with bootstrapping methodology, the authors have generated many millions of experimental linear calibration curves for the detection of rhodamine 6G tetrafluoroborate in ethanol solutions. The detection limits computed from them are in excellent agreement with both previously published theory and with comprehensive Monte Carlo computer simulations. Currie decision levels and Currie detection limits, each in the theoretical, chemical content domain, were found to be simply scaled reciprocals of the non-centrality parameter of the non-central t distribution that characterizes univariate linear calibration curves that have homoscedastic, additive Gaussian white noise. Accurate and precise estimates of the theoretical, content domain Currie detection limit for the experimental system, with 5% (each) probabilities of false positives and false negatives, are presented.
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Kermani, Bahram G
2016-07-01
Crystal Genetics, Inc. is an early-stage genetic test company, focused on achieving the highest possible clinical-grade accuracy and comprehensiveness for detecting germline (e.g., in hereditary cancer) and somatic (e.g., in early cancer detection) mutations. Crystal's mission is to significantly improve the health status of the population, by providing high accuracy, comprehensive, flexible and affordable genetic tests, primarily in cancer. Crystal's philosophy is that when it comes to detecting mutations that are strongly correlated with life-threatening diseases, the detection accuracy of every single mutation counts: a single false-positive error could cause severe anxiety for the patient. And, more importantly, a single false-negative error could potentially cost the patient's life. Crystal's objective is to eliminate both of these error types.
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A Method of Face Detection with Bayesian Probability
NASA Astrophysics Data System (ADS)
Sarker, Goutam
2010-10-01
The objective of face detection is to identify all images which contain a face, irrespective of its orientation, illumination conditions etc. This is a hard problem, because the faces are highly variable in size, shape lighting conditions etc. Many methods have been designed and developed to detect faces in a single image. The present paper is based on one `Appearance Based Method' which relies on learning the facial and non facial features from image examples. This in its turn is based on statistical analysis of examples and counter examples of facial images and employs Bayesian Conditional Classification Rule to detect the probability of belongingness of a face (or non-face) within an image frame. The detection rate of the present system is very high and thereby the number of false positive and false negative detection is substantially low.
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Zhou, Xiaodie; Song, Yong; Zhou, Xiaojun; Yu, Like; Wang, Jiandong
2015-01-01
Anaplastic lymphoma kinase (ALK) and echinoderm microtubule-associated protein-like 4 (EML4) gene rearrangements occur in approximately 5% of non-small-cell lung cancers (NSCLC), leading to the overexpression of anaplastic lymphoma kinase and predicting a response to the targeted inhibitor, crizotinib. Malignant pleural effusion occurs in most patients with advanced lung cancer, especially adenocarcinoma, and tissue samples are not always available from these patients. We attempted to clarify the feasibility of detecting the EML4-ALK fusion gene in pleural effusion cells using different methods. We obtained 66 samples of pleural effusion from NSCLC patients. The pleural effusion fluid was centrifuged, and the cellular components obtained were formalin fixed and paraffin embedded. The EML4-ALK fusion gene status was determined with fluorescent in situ hybridization (FISH), reverse transcription—polymerase chain reaction (RT-PCR), and immunohistochemistry (IHC). EML4-ALK was detected in three of 66 patient samples (4.5%) with RT-PCR. When the RT-PCR data were used as the standard, one false positive and one false negative samples were identified with IHC; and one false negative sample was identified with FISH. These results suggest that a block of pleural effusion cells can be used to detect the EML4-ALK fusion gene. IHC had good sensitivity, but low specificity. FISH had low sensitivity, but high specificity. RT-PCR is a good candidate method for detecting EML4-ALK in blocks of pleural effusion cells from lung cancer patients. PMID:25785456
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Liu, Leilei; Zhan, Ping; Zhou, Xiaodie; Song, Yong; Zhou, Xiaojun; Yu, Like; Wang, Jiandong
2015-01-01
Anaplastic lymphoma kinase (ALK) and echinoderm microtubule-associated protein-like 4 (EML4) gene rearrangements occur in approximately 5% of non-small-cell lung cancers (NSCLC), leading to the overexpression of anaplastic lymphoma kinase and predicting a response to the targeted inhibitor, crizotinib. Malignant pleural effusion occurs in most patients with advanced lung cancer, especially adenocarcinoma, and tissue samples are not always available from these patients. We attempted to clarify the feasibility of detecting the EML4-ALK fusion gene in pleural effusion cells using different methods. We obtained 66 samples of pleural effusion from NSCLC patients. The pleural effusion fluid was centrifuged, and the cellular components obtained were formalin fixed and paraffin embedded. The EML4-ALK fusion gene status was determined with fluorescent in situ hybridization (FISH), reverse transcription-polymerase chain reaction (RT-PCR), and immunohistochemistry (IHC). EML4-ALK was detected in three of 66 patient samples (4.5%) with RT-PCR. When the RT-PCR data were used as the standard, one false positive and one false negative samples were identified with IHC; and one false negative sample was identified with FISH. These results suggest that a block of pleural effusion cells can be used to detect the EML4-ALK fusion gene. IHC had good sensitivity, but low specificity. FISH had low sensitivity, but high specificity. RT-PCR is a good candidate method for detecting EML4-ALK in blocks of pleural effusion cells from lung cancer patients.
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Bion, Cindy; Beck Henzelin, Andrea; Qu, Yajuan; Pizzocri, Giuseppe; Bolzoni, Giuseppe; Buffoli, Elena
2016-01-01
Delvotest® T was evaluated for its capability at detecting residues of 27 antibiotics in raw cow's milk and in some dairy ingredients (skimmed and full-cream milk powders). The kit was used as a screening tool for the qualitative determination of antibiotics from different families in a single test. Results delivered by such a method are expressed as 'positive' or 'negative', referring to the claimed screening target concentration (STC). Validation was conducted according to the European Community Reference Laboratories' (CRLs) residues guidelines of 20 January 2010 and performed by two laboratories, one located in Europe and the other in Asia. Five criteria were evaluated including detection capability at STC, false-positive (FP) rate, false-negative (FN) rate, robustness and cross-reactivity using visual reading and Delvoscan®. STCs were set at or below the corresponding maximum residue limit (MRL), as fixed by European Regulation EC No. 37/2010. Four antibiotics (nafcillin, oxytetracycline, tetracycline and rifaximin) out of 27 had a false-negative rate ranging from 1.7% to 4.9%; however, it was still compliant with the CRLs' requirements. Globally, Delvotest T can be recommended for the analysis of the surveyed antibiotics in raw cow's milk, skimmed and full-cream milk powders. Additional compounds were tested such as sulfamethazine, spiramycin and erythromycin; however, detection at the corresponding MRL was not achievable and these compounds were removed from the validation. Other drugs from the sulfonamide, aminoglycoside or macrolide families not detected by the test at the MRL were not evaluated in this study. Regarding the reliability of this rapid test to milk-based preparations, additional experiments should be performed on a larger range of compounds and samples to validate the Delvotest T in such matrices.
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Is sequencing better than phenotypic tests for the detection of pyrazinamide resistance?
Bouzouita, I; Cabibbe, A M; Trovato, A; Draoui, H; Ghariani, A; Midouni, B; Essalah, L; Mehiri, E; Cirillo, D M; Slim-Saidi, L
2018-06-01
Phenotypic tests used to detect pyrazinamide (PZA) resistance are slow and have a high rate of false resistance. To evaluate the accuracy of pncA sequencing for the detection of PZA resistance in Mycobacterium tuberculosis strains isolated in Tunisia. A total of 82 isolates, 41 resistant and 41 susceptible to PZA on BACTEC™ MGIT™ 960, were sequenced for pncA. Whole genome sequencing was performed for strains that were phenotypically resistant and had wild-type pncA in addition to MGIT retesting with a modified protocol. Twenty-three strains resistant to PZA with negative pyrazinamidase (PZase) activity harboured a mutation in the promoter or coding region of pncA. However, 18 strains resistant to PZA did not present any mutation. Repeat MGIT 960 showed that 16 of 18 M. tuberculosis isolates were falsely resistant to PZA. Compared with MGIT, PZase activity assay and pncA sequencing both presented a sensitivity of 92.0% (95%CI 73.9-99.0) and a specificity of respectively 96.5% (positive predictive value [PPV] 92.0%, negative predictive value [NPV] 96.5%) and 100.0% (PPV 100.0%, NPV 96.6%). The standard MGIT assay showed a high rate of false resistance to PZA, and the PZase activity assay is slow. pncA sequencing could therefore represent a rapid, accurate, alternative test to detect PZA resistance.
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Beynon, C M; Sumnall, H R; McVeigh, J; Cole, J C; Bellis, M A
2006-10-01
Assessment of the sensitivity and specificity of two commercially available 'drug-facilitated sexual assault' drug detector kits, Drink Guard and Drink Detective. Experimental. Laboratory. Gamma hydroxybutyrate (GHB) sodium salt, ketamine hydrochloride, temazepam, flunitrazepam and diazepam were dissolved (Tween added to benzodiazepine solutions) as separate stock solutions and added to 330 ml samples of cola (Pepsi Max), beer (Stella Artois), 'alcopop' (Bacardi Breezer) and placebo (distilled water). The doses used are reported to be common in cases of intoxication. Each kit was tested 10 times for each drink/drug combination. Two blind, independent observers scored each test (presence/absence of drug) in accordance with kit instructions; chi 2 was used to compare the proportion of times raters scored tests correctly and incorrectly. Sensitivity and specificity were calculated overall, for each drink, and sensitivity was calculated for each drug. Inter-observer agreement was evaluated using the kappa statistic. While both raters were able to score significantly more tests correctly than incorrectly using Drink Detective, and one rater scored similarly using Drink Guard, the overall sensitivity of Drink Detective and Drink Guard was 69.0% (95% CI 64.2-73.5%) and 37.5% (95% CI 30.1-45.5%), respectively. Sensitivity was drink-dependent. Drink Detective was unable to detect our dose of GHB in water, with all tests scored negatively by both raters for this drink/drug combination (n = 20 negative scores). Overall, specificity was 76.6% (95% CI 71.5-81.0%) and 87.9% (95% CI 83.0-91.6%) for Drink Guard and Drink Detective, respectively, but was affected by the beverage. Inter-rater agreement was poor for Drink Guard (kappa = 0.278 +/- 0.069) but excellent for Drink Detective (kappa = 0.894 +/- 0.245). Inter-observer agreement was drug-dependent. Use of drug detector kits by the public in the night-time environment needs further investigation and may create a false sense of security (false negatives) and undue concern (false positives) among kit users.
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False Negatives for Remote Life Detection on Ocean-Bearing Planets: Lessons from the Early Earth
NASA Astrophysics Data System (ADS)
Reinhard, Christopher T.; Olson, Stephanie L.; Schwieterman, Edward W.; Lyons, Timothy W.
2017-04-01
Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes throughout its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal of work has centered on refining our understanding of false positives for remote life detection, much less attention has been paid to the possibility of false negatives, that is, cryptic biospheres that are widespread and active on a planet's surface but are ultimately undetectable or difficult to detect in the composition of a planet's atmosphere. Here, we summarize recent developments from geochemical proxy records and Earth system models that provide insight into the long-term evolution of the most readily detectable potential biosignature gases on Earth - oxygen (O2), ozone (O3), and methane (CH4). We suggest that the canonical O2-CH4 disequilibrium biosignature would perhaps have been challenging to detect remotely during Earth's ˜4.5-billion-year history and that in general atmospheric O2/O3 levels have been a poor proxy for the presence of Earth's biosphere for all but the last ˜500 million years. We further suggest that detecting atmospheric CH4 would have been problematic for most of the last ˜2.5 billion years of Earth's history. More broadly, we stress that internal oceanic recycling of biosignature gases will often render surface biospheres on ocean-bearing silicate worlds cryptic, with the implication that the planets most conducive to the development and maintenance of a pervasive biosphere will often be challenging to characterize via conventional atmospheric biosignatures.
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Díaz, Pedro Berzosa; Lozano, Patricia Mula; Rincón, Jose Manuel Ramos; García, Luz; Reyes, Francisco; Llanes, Agustín Benito
2015-09-18
Approximately 50 million people (60 %) live in malaria risk areas in Ethiopia, at altitudes below 2000 m. According to official data, 60-70 % of malaria cases are due to Plasmodium falciparum, and 40-30 % by Plasmodium vivax. The species Plasmodium ovale was detected in 2013 in the northwest of the country, being the first report of the presence of this species in Ethiopia since the 60 s. The aim of this study was to assess the diagnosis by microscopy and PCR, and demonstrate the presence of other Plasmodium species in the country. The survey was conducted in Bulbula, situated in the Rift Valley (West Arsi Province, Oromia Region). From December 2010 to October 2011, 3060 samples were collected from patients with symptoms of malaria; the diagnosis of malaria was done by microscopy and confirmation by PCR. 736 samples were positive for malaria by microscopy. After removing the 260 samples (109 positives and 151 negatives) for which it was not possible to do PCR, there were a total of 2800 samples, 1209 are used for its confirmation by PCR and quality control (627 are positives and 582 negatives by microscopy). From the 627 positive samples, 604 were confirmed as positive by PCR, 23 false positives were detected, and the group of 582 negative samples, 184 were positive by PCR (false negatives), which added to the previous positive samples is a total of 788, positive samples for some species of Plasmodium sp. 13.3 % more positives were detected with the PCR than the microscopy. Importantly, 23 samples were detected by PCR as P. ovale, after the sequencing of these samples was determined as P. ovale curtisi. The PCR detected more positive samples than the microscopy; in addition, P. ovale and P. ovale/P. vivax were detected that had not been detected by microscopy, which can affect in the infection control.
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Lavoie, S; Caswell, D; Gill, M J; Kadkhoda, K; Charlton, C L; Levett, P N; Hatchette, T; Garceau, R; Maregmen, J; Mazzulli, T; Needle, R; Kadivar, K; Kim, J
2018-07-01
False-reactivity in HIV-negative specimens has been detected in HIV fourth-generation antigen/antibody or 'combo' assays which are able to detect both anti-HIV-1/HIV-2 antibodies and HIV-1 antigen. We sought to characterize these specimens and determine the effect of heterophilic interference. Specimens previously testing as false-reactive on the Abbott ARCHITECT HIV Ag/Ab combo assay and re-tested on a different (Siemens ADVIA Centaur HIV Ag/Ab) assay. A subset of these specimens were also pre-treated with heterophilic blocking agents and re-tested on the Abbott assay. Here we report that 95% (252/264) of clinical specimens that were repeatedly reactive on the Abbott ARCHITECT HIV Ag/Ab combo assay (S/Co range, 0.94-678) were negative when re-tested on a different fourth generation HIV combo assay (Siemens ADVIA Centaur HIV Ag/Ab). All 264 samples were subsequently confirmed to be HIV negative. On a small subset (57) of specimens with available volume, pre-treatment with two different reagents (HBT; Heterophilic Blocking Tube, NABT; Non-Specific Blocking Tube) designed to block heterophilic antibody interference either eliminated (HBT) or reduced (NABT) the false reactivity when re-tested on the ARCHITECT HIV Ag/Ab combo assay. Our results suggest that the Abbott ARCHITECT HIV Ag/Ab combo assay can be prone to heterophilic antibody interference. Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.
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A case of placental trisomy 18 mosaicism causing a false negative NIPT result.
Yang, Jiexia; Qi, Yiming; Guo, Fangfang; Hou, Yaping; Peng, Haishan; Wang, Dongmei; Oy, Haoxin; Yin, Aihua
2017-01-01
The non-invasive prenatal testing that evaluates circulating cell free DNA, and has been established as an additional pregnancy test for detecting the common fetal trisomies 21, 18 and 13 is rapidly revolutionizing prenatal screening as a result of its increased sensitivity and specificity. However, false positive and false negative results still exist. We presented a case in which the non-invasive prenatal testing results were normal at 15 gestational age (GA), but an ultrasound examination at 30GA showed that the fetus had heart abnormalities, and the third trimester ultrasound at 33GA noted multiple anomalies including a 3.0 mm ventricular septal defect. Along with cordocentesis at 33GA, the cord blood sample cytogenetics analysis showed a mos 47,XN,+18[61]/46,XN[39] T18 karyotype. Six placental biopsies confirmed that the chromosome 18 placenta chimerism ratio had changed from 33% to 72%. Ultimately, the pregnancy was interrupted at 34GA. We presented this case to highlight the need to clearly explain false positive or false negative results to patients. We believe that this information will also influence the development of future diagnostic test methodologies.
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A Protocol Layer Trust-Based Intrusion Detection Scheme for Wireless Sensor Networks
Wang, Jian; Jiang, Shuai; Fapojuwo, Abraham O.
2017-01-01
This article proposes a protocol layer trust-based intrusion detection scheme for wireless sensor networks. Unlike existing work, the trust value of a sensor node is evaluated according to the deviations of key parameters at each protocol layer considering the attacks initiated at different protocol layers will inevitably have impacts on the parameters of the corresponding protocol layers. For simplicity, the paper mainly considers three aspects of trustworthiness, namely physical layer trust, media access control layer trust and network layer trust. The per-layer trust metrics are then combined to determine the overall trust metric of a sensor node. The performance of the proposed intrusion detection mechanism is then analyzed using the t-distribution to derive analytical results of false positive and false negative probabilities. Numerical analytical results, validated by simulation results, are presented in different attack scenarios. It is shown that the proposed protocol layer trust-based intrusion detection scheme outperforms a state-of-the-art scheme in terms of detection probability and false probability, demonstrating its usefulness for detecting cross-layer attacks. PMID:28555023
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A Protocol Layer Trust-Based Intrusion Detection Scheme for Wireless Sensor Networks.
Wang, Jian; Jiang, Shuai; Fapojuwo, Abraham O
2017-05-27
This article proposes a protocol layer trust-based intrusion detection scheme for wireless sensor networks. Unlike existing work, the trust value of a sensor node is evaluated according to the deviations of key parameters at each protocol layer considering the attacks initiated at different protocol layers will inevitably have impacts on the parameters of the corresponding protocol layers. For simplicity, the paper mainly considers three aspects of trustworthiness, namely physical layer trust, media access control layer trust and network layer trust. The per-layer trust metrics are then combined to determine the overall trust metric of a sensor node. The performance of the proposed intrusion detection mechanism is then analyzed using the t-distribution to derive analytical results of false positive and false negative probabilities. Numerical analytical results, validated by simulation results, are presented in different attack scenarios. It is shown that the proposed protocol layer trust-based intrusion detection scheme outperforms a state-of-the-art scheme in terms of detection probability and false probability, demonstrating its usefulness for detecting cross-layer attacks.
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Development of novel Alicyclobacillus spp. isolation medium.
Chang, S; Kang, D-H
2005-01-01
To develop a new isolation medium with higher recovery rates of Alicyclobacillus spp. SK agar was developed with optimized incubation temperature, pH, acidulant, Tween 80 concentration and divalent cation addition. Results indicate that detection of Alicyclobacillus spp. by SK agar was significantly higher (P > 0.05) than those obtained by K agar, orange serum agar, and potato dextrose agar. Current media used for Alicyclobacillus spp. isolation still resulted in high numbers of false negative products. The sensitivity of SK agar to Alicyclobacillus spp. allows detection of low numbers of Alicyclobacillus spp. and also provides a more higher isolation results compared with currently used media. SK agar will be useful to the fruit juice industry to obtain more accurate numbers of contaminant Alicyclobacillus spp. With this media, false negative samples can be reduced, and the likelihood of exported products being rejected can be greatly reduced.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Haase, G.M.; Sfakianakis, G.N.; Lobe, T.E.
1981-06-01
The ability of external imaging to demonstrate intestinal infarction in neonatal necrotizing enterocolitis (NEC) was prospectively evaluated. The radiopharmaceutical technetium--99m diphosphonate was injected intravenously and the patients subsequently underwent abdominal scanning. Clinical patient care and interpretation of the images were entirely independent throughout the study. Of 33 studies, 7 were positive, 4 were suspicious, and 22 were negative. One false positive study detected ischemia without transmural infarction. The second false positive scan occurred postoperatively and was due to misinterpretation of the hyperactivity along the surgical incision. None of the suspicious cases had damaged bowel. The two false negative studies clearlymore » failed to demonstrate frank intestinal necrosis. The presence of very small areas of infarction, errors in technical settings, subjective interpretation of scans and delayed clearance of the radionuclide in a critically ill neonate may all limit the accuracy of external abdominal scanning. However, in spite of an error rate of 12%, it is likely that this technique will enhance the present clinical, laboratory, and radiologic parameters of patient management in NEC.« less
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Whiley, Harriet
2016-12-24
Legionella is an opportunistic pathogen of public health significance. One of the main sources of Legionella is potable water systems. As a consequence of aging populations there is an increasing demographic considered at high risk for Legionellosis and, as such, a review of the guidelines is required. Worldwide, Legionella has been detected from many potable water sources, suggesting it is ubiquitous in this environment. Previous studies have identified the limitations of the current standard method for Legionella detection and the high possibility of it returning both false negative and false positive results. There is also huge variability in Legionella test results for the same water sample when conducted at different laboratories. However, many guidelines still recommend the testing of water systems. This commentary argues for the removal of routine Legionella monitoring from all water distribution guidelines. This procedure is financially consuming and false negatives may result in managers being over-confident with a system or a control mechanism. Instead, the presence of the pathogen should be assumed and focus spent on managing appropriate control measures and protecting high-risk population groups.
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Whiley, Harriet
2016-01-01
Legionella is an opportunistic pathogen of public health significance. One of the main sources of Legionella is potable water systems. As a consequence of aging populations there is an increasing demographic considered at high risk for Legionellosis and, as such, a review of the guidelines is required. Worldwide, Legionella has been detected from many potable water sources, suggesting it is ubiquitous in this environment. Previous studies have identified the limitations of the current standard method for Legionella detection and the high possibility of it returning both false negative and false positive results. There is also huge variability in Legionella test results for the same water sample when conducted at different laboratories. However, many guidelines still recommend the testing of water systems. This commentary argues for the removal of routine Legionella monitoring from all water distribution guidelines. This procedure is financially consuming and false negatives may result in managers being over-confident with a system or a control mechanism. Instead, the presence of the pathogen should be assumed and focus spent on managing appropriate control measures and protecting high-risk population groups. PMID:28029126
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Arthur, Terrance M; Bosilevac, Joseph M; Nou, Xiangwu; Koohmaraie, Mohammad
2005-08-01
Currently, several beef processors employ test-and-hold systems for increased quality control of ground beef. In such programs, each lot of product must be tested and found negative for Escherichia coli O157:H7 prior to release of the product into commerce. Optimization of three testing attributes (detection time, specificity, and sensitivity) is critical to the success of such strategies. Because ground beef is a highly perishable product, the testing methodology used must be as rapid as possible. The test also must have a low false-positive result rate so product is not needlessly discarded. False-negative results cannot be tolerated because they would allow contaminated product to be released and potentially cause disease. In this study, two culture-based and three PCR-based methods for detecting E. coli O157:H7 in ground beef were compared for their abilities to meet the above criteria. Ground beef samples were individually spiked with five genetically distinct strains of E. coli O157: H7 at concentrations of 17 and 1.7 CFU/65 g and then subjected to the various testing methodologies. There was no difference (P > 0.05) in the abilities of the PCR-based methods to detect E. coli O157:H7 inoculated in ground beef at 1.7 CFU/65 g. The culture-based systems detected more positive samples than did the PCR-based systems, but the detection times (21 to 48 h) were at least 9 h longer than those for the PCR-based methods (7.5 to 12 h). Ground beef samples were also spiked with potentially cross-reactive strains. The PCR-based systems that employed an immunomagnetic separation step prior to detection produced fewer false-positive results.
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Parallel evaluation of broad virus detection methods.
Modrof, Jens; Berting, Andreas; Kreil, Thomas R
2014-01-01
The testing for adventitious viruses is of critical importance during development and production of biological products. The recent emergence and ongoing development of broad virus detection methods calls for an evaluation of whether these methods can appropriately be implemented into current adventitious agent testing procedures. To assess the suitability of several broad virus detection methods, a comparative experimental study was conducted: four virus preparations, which were spiked at two different concentrations each into two different cell culture media, were sent to four investigators in a blinded fashion for analysis with broad virus detection methods such as polymerase chain reaction-electrospray ionization mass spectrometry (PCR-ESI/MS), microarray, and two approaches utilizing massively parallel sequencing. The results that were reported by the investigators revealed that all methods were able to identify the majority of samples correctly (mean 83%), with a surprisingly narrow range among the methods, that is, between 72% (PCR-ESI/MS) and 95% (microarray). In addition to the correct results, a variety of unexpected assignments were reported for a minority of samples, again with little variation regarding the methods used (range 20-45%), while false negatives were reported for 0-25% of the samples. Regarding assay sensitivity, the viruses were detected by all methods included in this study at concentrations of about 4-5 log10 quantitative PCR copies/mL, and probably with higher sensitivity in some cases. In summary, the broad virus detection methods investigated were shown to be suitable even for detection of relatively low virus concentrations. However, there is also some potential for the production of false-positive as well as false-negative assignments, which indicates the requirement for further improvements before these methods can be considered for routine use. © PDA, Inc. 2014.
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Gura, Sigalit; Guerra-Diaz, Patricia; Lai, Hanh; Almirall, José R
2009-07-01
Trace detection of illicit drugs challenges the scientific community to develop improved sensitivity and selectivity in sampling and detection techniques. Ion mobility spectrometry (IMS) is one of the prominent trace detectors for illicit drugs and explosives, mostly due to its portability, high sensitivity and fast analysis. Current sampling methods for IMS rely on wiping suspected surfaces or withdrawing air through filters to collect particulates. These methods depend greatly on the particulates being bound onto surfaces or having sufficient vapour pressure to be airborne. Many of these compounds are not readily available in the headspace due to their low vapour pressure. This research presents a novel SPME device for enhanced air sampling and shows the use of optimized IMS by genetic algorithms to target volatile markers and/or odour signatures of illicit substances. The sampling method was based on unique static samplers, planar substrates coated with sol-gel polydimethyl siloxane (PDMS) nanoparticles, also known as planar solid-phase microextraction (PSPME). Due to its surface chemistry, high surface area and capacity, PSPME provides significant increases in sensitivity over conventional fibre SPME. The results show a 50-400 times increase in the detection capacity for piperonal, the odour signature of 3,4-methylenedioxymethamphetamine (MDMA). The PSPME-IMS technique was able to detect 600 ng of piperonal in a 30 s extraction from a quart-sized can containing 5 MDMA tablets, while detection using fibre SPME-IMS was not attainable. In a blind study of six cases suspected to contain varying amounts of MDMA in the tablets, PSPME-IMS successfully detected five positive cases and also produced no false positives or false negatives. One positive case had minimal amounts of MDMA resulting in a false negative response for fibre SPME-IMS.
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Berhane, Araia; Anderson, Karen; Mihreteab, Selam; Gresty, Karryn; Rogier, Eric; Mohamed, Salih; Hagos, Filmon; Embaye, Ghirmay; Chinorumba, Anderson; Zehaie, Assefash; Dowd, Simone; Waters, Norman C.; Gatton, Michelle L.; Udhayakumar, Venkatachalam; Cunningham, Jane
2018-01-01
False-negative results for Plasmodium falciparum histidine-rich protein (HRP) 2–based rapid diagnostic tests (RDTs) are increasing in Eritrea. We investigated HRP gene 2/3 (pfhrp2/pfhrp3) status in 50 infected patients at 2 hospitals. We showed that 80.8% (21/26) of patients at Ghindae Hospital and 41.7% (10/24) at Massawa Hospital were infected with pfhrp2-negative parasites and 92.3% (24/26) of patients at Ghindae Hospital and 70.8% (17/24) at Massawa Hospital were infected with pfhrp3-negative parasites. Parasite densities between pfhrp2-positive and pfhrp2-negative patients were comparable. All pfhrp2-negative samples had no detectable HRP2/3 antigen and showed negative results for HRP2-based RDTs. pfhrp2-negative parasites were genetically less diverse and formed 2 clusters with no close relationships to parasites from Peru. These parasites probably emerged independently by selection in Eritrea. High prevalence of pfhrp2-negative parasites caused a high rate of false-negative results for RDTs. Determining prevalence of pfhrp2-negative parasites is urgently needed in neighboring countries to assist case management policies. PMID:29460730
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Berhane, Araia; Anderson, Karen; Mihreteab, Selam; Gresty, Karryn; Rogier, Eric; Mohamed, Salih; Hagos, Filmon; Embaye, Ghirmay; Chinorumba, Anderson; Zehaie, Assefash; Dowd, Simone; Waters, Norman C; Gatton, Michelle L; Udhayakumar, Venkatachalam; Cheng, Qin; Cunningham, Jane
2018-03-01
False-negative results for Plasmodium falciparum histidine-rich protein (HRP) 2-based rapid diagnostic tests (RDTs) are increasing in Eritrea. We investigated HRP gene 2/3 (pfhrp2/pfhrp3) status in 50 infected patients at 2 hospitals. We showed that 80.8% (21/26) of patients at Ghindae Hospital and 41.7% (10/24) at Massawa Hospital were infected with pfhrp2-negative parasites and 92.3% (24/26) of patients at Ghindae Hospital and 70.8% (17/24) at Massawa Hospital were infected with pfhrp3-negative parasites. Parasite densities between pfhrp2-positive and pfhrp2-negative patients were comparable. All pfhrp2-negative samples had no detectable HRP2/3 antigen and showed negative results for HRP2-based RDTs. pfhrp2-negative parasites were genetically less diverse and formed 2 clusters with no close relationships to parasites from Peru. These parasites probably emerged independently by selection in Eritrea. High prevalence of pfhrp2-negative parasites caused a high rate of false-negative results for RDTs. Determining prevalence of pfhrp2-negative parasites is urgently needed in neighboring countries to assist case management policies.
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Wang, Li-jun; Lu, Xin-xin; Wu, Wei; Sui, Wen-jun; Zhang, Gui
2014-01-01
In order to evaluate a rapid matrix-assisted laser desorption ionization-time of flight mass spectrometry (MAIDI-TOF MS) assay in screening vancomycin-resistant Enterococcus faecium, a total of 150 E. faecium clinical strains were studied, including 60 vancomycin-resistant E. faecium (VREF) isolates and 90 vancomycin-susceptible (VSEF) strains. Vancomycin resistance genes were detected by sequencing. E. faecium were identified by MALDI-TOF MS. A genetic algorithm model with ClinProTools software was generated using spectra of 30 VREF isolates and 30 VSEF isolates. Using this model, 90 test isolates were discriminated between VREF and VSEF. The results showed that all sixty VREF isolates carried the vanA gene. The performance of VREF detection by the genetic algorithm model of MALDI-TOF MS compared to the sequencing method was sensitivity = 80%, specificity = 90%, false positive rate =10%, false negative rate =10%, positive predictive value = 80%, negative predictive value= 90%. MALDI-TOF MS can be used as a screening test for discrimination between vanA-positive E. faecium and vanA-negative E. faecium.
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Childress, Carolyn J. Oblinger; Foreman, William T.; Connor, Brooke F.; Maloney, Thomas J.
1999-01-01
This report describes the U.S. Geological Survey National Water Quality Laboratory?s approach for determining long-term method detection levels and establishing reporting levels, details relevant new reporting conventions, and provides preliminary guidance on interpreting data reported with the new conventions. At the long-term method detection level concentration, the risk of a false positive detection (analyte reported present at the long-term method detection level when not in sample) is no more than 1 percent. However, at the long-term method detection level, the risk of a false negative occurrence (analyte reported not present when present at the long-term method detection level concentration) is up to 50 percent. Because this false negative rate is too high for use as a default 'less than' reporting level, a more reliable laboratory reporting level is set at twice the determined long-term method detection level. For all methods, concentrations measured between the laboratory reporting level and the long-term method detection level will be reported as estimated concentrations. Non-detections will be censored to the laboratory reporting level. Adoption of the new reporting conventions requires a full understanding of how low-concentration data can be used and interpreted and places responsibility for using and presenting final data with the user rather than with the laboratory. Users must consider that (1) new laboratory reporting levels may differ from previously established minimum reporting levels, (2) long-term method detection levels and laboratory reporting levels may change over time, and (3) estimated concentrations are less certain than concentrations reported above the laboratory reporting level. The availability of uncensored but qualified low-concentration data for interpretation and statistical analysis is a substantial benefit to the user. A decision to censor data after they are reported from the laboratory may still be made by the user, if merited, on the basis of the intended use of the data.
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Daxboeck, Florian; Dornbusch, Hans Jürgen; Krause, Robert; Assadian, Ojan; Wenisch, Christoph
2004-01-01
A small but significant proportion of blood cultures processed by the BACTEC 9000 series systems is signaled positive, while subsequent Gram's stain and culture on solid media yield no pathogens. In this study, 15 "false-positive" vials (7 aerobes, 8 anaerobes) from 15 patients were investigated for the presence of bacteria and fungi by eubacterial 16S rDNA and panfungal 18S rDNA amplification, respectively. All samples turned out negative by both methods. Most patients (7) had neutropenia, which does not support the theory that high leukocyte counts enhance the generation of false-positive results. In conclusion, the results of this study indicate that false-negative results generated by the BACTEC 9000 series are inherent to the automated detection and not due to the growth of fastidious organisms.
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Fusion of local and global detection systems to detect tuberculosis in chest radiographs.
Hogeweg, Laurens; Mol, Christian; de Jong, Pim A; Dawson, Rodney; Ayles, Helen; van Ginneken, Bramin
2010-01-01
Automatic detection of tuberculosis (TB) on chest radiographs is a difficult problem because of the diverse presentation of the disease. A combination of detection systems for abnormalities and normal anatomy is used to improve detection performance. A textural abnormality detection system operating at the pixel level is combined with a clavicle detection system to suppress false positive responses. The output of a shape abnormality detection system operating at the image level is combined in a next step to further improve performance by reducing false negatives. Strategies for combining systems based on serial and parallel configurations were evaluated using the minimum, maximum, product, and mean probability combination rules. The performance of TB detection increased, as measured using the area under the ROC curve, from 0.67 for the textural abnormality detection system alone to 0.86 when the three systems were combined. The best result was achieved using the sum and product rule in a parallel combination of outputs.
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Zhao, Bo; Wang, Yan-Yan; Cao, Yun; Zhang, Hui-Qin; Zhu, Xing-Quan; He, Yong-Kang; Xia, Chao-Ming
2015-01-01
Background Schistosomiasis has decreased significantly in prevalence and intensity of infection in China, thus more accurate and sensitive methods are desperately needed for the further control of schistosomiasis. The present work aimed to assess the utility of the loop-mediated isothermal amplification (LAMP) for detection of light intensity infection or false-negative patients and patients post-treatment, targeting the highly repetitive retrotransposon SjR2 of Schistosoma japonicum. Methodology/ Principal Findings LAMP was first assessed in rabbits with low intensity infection (EPG<10). Then 110 patient sera from Hunan Province, China, and 47 sera after treatment by praziquantel were used to evaluate the diagnostic validity of LAMP. Meanwhile, 42 sera from healthy individuals in a non-endemic area, and 60 sera from "healthy” residents who were identified as being negative for feces examination and immuno-methods in an endemic area were also examined. The results showed that LAMP could detect S. japonicum DNA in sera from rabbits at 3rd day post-infection. Following administration of praziquantel, the S. japonicum DNA in rabbit sera became negative at 10 weeks post-treatment. Of 110 sera from patients, LAMP showed 95.5% sensitivity, and even for 41 patients with less than 10 EPG, the sensitivity of LAMP still reached to 95.1%. For 47 patients after treatment, the negative conversion rate of S. japonicum DNA in patient sera increased from 23.4%, 61.7% to 83.0% at 3 months, 6 months and 9 months post-treatment, respectively. No false-positive result was obtained for 42 human sera from non-endemic area, while for the 60 “healthy” individuals from endemic area, 10 (16.7%) individuals were positive by LAMP, which suggested that these individuals might be false-negative patients. Conclusions/ Significance The present study demonstrated that the LAMP assay is sensitive, specific, and affordable, which would help reduce schistosomiasis transmission through targeted treatment of individuals, particularly for those with negative stool examinations who may yet remain infected. The LAMP assay may provide a potential tool to support schistosomiasis control and elimination strategies. PMID:25874964
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Xu, Jing; Guan, Zhi-Xun; Zhao, Bo; Wang, Yan-Yan; Cao, Yun; Zhang, Hui-Qin; Zhu, Xing-Quan; He, Yong-Kang; Xia, Chao-Ming
2015-04-01
Schistosomiasis has decreased significantly in prevalence and intensity of infection in China, thus more accurate and sensitive methods are desperately needed for the further control of schistosomiasis. The present work aimed to assess the utility of the loop-mediated isothermal amplification (LAMP) for detection of light intensity infection or false-negative patients and patients post-treatment, targeting the highly repetitive retrotransposon SjR2 of Schistosoma japonicum. LAMP was first assessed in rabbits with low intensity infection (EPG<10). Then 110 patient sera from Hunan Province, China, and 47 sera after treatment by praziquantel were used to evaluate the diagnostic validity of LAMP. Meanwhile, 42 sera from healthy individuals in a non-endemic area, and 60 sera from "healthy" residents who were identified as being negative for feces examination and immuno-methods in an endemic area were also examined. The results showed that LAMP could detect S. japonicum DNA in sera from rabbits at 3rd day post-infection. Following administration of praziquantel, the S. japonicum DNA in rabbit sera became negative at 10 weeks post-treatment. Of 110 sera from patients, LAMP showed 95.5% sensitivity, and even for 41 patients with less than 10 EPG, the sensitivity of LAMP still reached to 95.1%. For 47 patients after treatment, the negative conversion rate of S. japonicum DNA in patient sera increased from 23.4%, 61.7% to 83.0% at 3 months, 6 months and 9 months post-treatment, respectively. No false-positive result was obtained for 42 human sera from non-endemic area, while for the 60 "healthy" individuals from endemic area, 10 (16.7%) individuals were positive by LAMP, which suggested that these individuals might be false-negative patients. The present study demonstrated that the LAMP assay is sensitive, specific, and affordable, which would help reduce schistosomiasis transmission through targeted treatment of individuals, particularly for those with negative stool examinations who may yet remain infected. The LAMP assay may provide a potential tool to support schistosomiasis control and elimination strategies.
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Imperfect pathogen detection from non-invasive skin swabs biases disease inference
DiRenzo, Graziella V.; Grant, Evan H. Campbell; Longo, Ana; Che-Castaldo, Christian; Zamudio, Kelly R.; Lips, Karen
2018-01-01
1. Conservation managers rely on accurate estimates of disease parameters, such as pathogen prevalence and infection intensity, to assess disease status of a host population. However, these disease metrics may be biased if low-level infection intensities are missed by sampling methods or laboratory diagnostic tests. These false negatives underestimate pathogen prevalence and overestimate mean infection intensity of infected individuals. 2. Our objectives were two-fold. First, we quantified false negative error rates of Batrachochytrium dendrobatidis on non-invasive skin swabs collected from an amphibian community in El Copé, Panama. We swabbed amphibians twice in sequence, and we used a recently developed hierarchical Bayesian estimator to assess disease status of the population. Second, we developed a novel hierarchical Bayesian model to simultaneously account for imperfect pathogen detection from field sampling and laboratory diagnostic testing. We evaluated the performance of the model using simulations and varying sampling design to quantify the magnitude of bias in estimates of pathogen prevalence and infection intensity. 3. We show that Bd detection probability from skin swabs was related to host infection intensity, where Bd infections < 10 zoospores have < 95% probability of being detected. If imperfect Bd detection was not considered, then Bd prevalence was underestimated by as much as 16%. In the Bd-amphibian system, this indicates a need to correct for imperfect pathogen detection caused by skin swabs in persisting host communities with low-level infections. More generally, our results have implications for study designs in other disease systems, particularly those with similar objectives, biology, and sampling decisions. 4. Uncertainty in pathogen detection is an inherent property of most sampling protocols and diagnostic tests, where the magnitude of bias depends on the study system, type of infection, and false negative error rates. Given that it may be difficult to know this information in advance, we advocate that the most cautious approach is to assume all errors are possible and to accommodate them by adjusting sampling designs. The modeling framework presented here improves the accuracy in estimating pathogen prevalence and infection intensity.
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NASA Astrophysics Data System (ADS)
Zhang, Dongbo; Peng, Yinghui; Yi, Yao; Shang, Xingyu
2013-10-01
Detection of red lesions [hemorrhages (HRs) and microaneurysms (MAs)] is crucial for the diagnosis of early diabetic retinopathy. A method based on background estimation and adapted to specific characteristics of HRs and MAs is proposed. Candidate red lesions are located by background estimation and Mahalanobis distance measure and then some adaptive postprocessing techniques, which include vessel detection, nonvessel exclusion based on shape analysis, and noise points exclusion by double-ring filter (only used for MAs detection), are conducted to remove nonlesion pixels. The method is evaluated on our collected image dataset, and experimental results show that it is better than or approximate to other previous approaches. It is effective to reduce the false-positive and false-negative results that arise from incomplete and inaccurate vessel structure.
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Salter, Robert; Holmes, Steven; Legg, David; Coble, Joel; George, Bruce
2012-02-01
Pork tissue samples that tested positive and negative by the Charm II tetracycline test screening method in the slaughter plant laboratory were tested with the modified AOAC International liquid chromatography tandem mass spectrometry (LC-MS-MS) method 995.09 to determine the predictive value of the screening method at detecting total tetracyclines at 10 μg/kg of tissue, in compliance with Russian import regulations. There were 218 presumptive-positive tetracycline samples of 4,195 randomly tested hogs. Of these screening test positive samples, 83% (182) were positive, >10 μg/kg by LC-MS-MS; 12.8% (28) were false violative, greater than limit of detection (LOD) but <10 μg/kg; and 4.2% (8) were not detected at the LC-MS-MS LOD. The 36 false-violative and not-detected samples represent 1% of the total samples screened. Twenty-seven of 30 randomly selected tetracycline screening negative samples tested below the LC-MS-MS LOD, and 3 samples tested <3 μg/kg chlortetracycline. Results indicate that the Charm II tetracycline test is effective at predicting hogs containing >10 μg/kg total tetracyclines in compliance with Russian import regulations.
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Dasgupta, Amitava; Wahed, Amer; Wells, Alice
2002-02-01
Several adulterants are used to mask tests for abused drugs in urine. Adulterants such as "Klear" and "Whizzies" contain potassium nitrite, and "Urine Luck" contains pyridinium chlorochromate (PCC). The presence of these adulterants cannot be detected by routine specimen integrity checks (pH, specific gravity, and temperature). We developed rapid spot tests for detecting these adulterants in urine. Addition of 3% hydrogen peroxide in urine adulterated with PCC caused rapid formation of a dark brown color. In contrast, unadulterated urine turned colorless when hydrogen peroxide was added. When urine contaminated with nitrite and 2 to 3 drops of 2N hydrochloric acid were added to 2% aqueous potassium permanganate solution, the dark pink permanganate solution turned colorless immediately with effervescence. Urine contaminated with nitrite liberated iodine from potassium iodide solution in the presence of 2N hydrochloric acid. Urine adulterated with PCC also liberated iodine from potassium iodide in acid medium but did not turn potassium permanganate solution colorless. Urine specimens from volunteers and random urine samples that tested negative for drugs did not cause false-positive results. These rapid spot tests are useful for detecting adulterated urine to avoid false-negative drug tests.
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A soft kinetic data structure for lesion border detection.
Kockara, Sinan; Mete, Mutlu; Yip, Vincent; Lee, Brendan; Aydin, Kemal
2010-06-15
The medical imaging and image processing techniques, ranging from microscopic to macroscopic, has become one of the main components of diagnostic procedures to assist dermatologists in their medical decision-making processes. Computer-aided segmentation and border detection on dermoscopic images is one of the core components of diagnostic procedures and therapeutic interventions for skin cancer. Automated assessment tools for dermoscopic images have become an important research field mainly because of inter- and intra-observer variations in human interpretations. In this study, a novel approach-graph spanner-for automatic border detection in dermoscopic images is proposed. In this approach, a proximity graph representation of dermoscopic images in order to detect regions and borders in skin lesion is presented. Graph spanner approach is examined on a set of 100 dermoscopic images whose manually drawn borders by a dermatologist are used as the ground truth. Error rates, false positives and false negatives along with true positives and true negatives are quantified by digitally comparing results with manually determined borders from a dermatologist. The results show that the highest precision and recall rates obtained to determine lesion boundaries are 100%. However, accuracy of assessment averages out at 97.72% and borders errors' mean is 2.28% for whole dataset.
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NASA Technical Reports Server (NTRS)
Melcher, Kevin J.; Cruz, Jose A.; Johnson Stephen B.; Lo, Yunnhon
2015-01-01
This paper describes a quantitative methodology for bounding the false positive (FP) and false negative (FN) probabilities associated with a human-rated launch vehicle abort trigger (AT) that includes sensor data qualification (SDQ). In this context, an AT is a hardware and software mechanism designed to detect the existence of a specific abort condition. Also, SDQ is an algorithmic approach used to identify sensor data suspected of being corrupt so that suspect data does not adversely affect an AT's detection capability. The FP and FN methodologies presented here were developed to support estimation of the probabilities of loss of crew and loss of mission for the Space Launch System (SLS) which is being developed by the National Aeronautics and Space Administration (NASA). The paper provides a brief overview of system health management as being an extension of control theory; and describes how ATs and the calculation of FP and FN probabilities relate to this theory. The discussion leads to a detailed presentation of the FP and FN methodology and an example showing how the FP and FN calculations are performed. This detailed presentation includes a methodology for calculating the change in FP and FN probabilities that result from including SDQ in the AT architecture. To avoid proprietary and sensitive data issues, the example incorporates a mixture of open literature and fictitious reliability data. Results presented in the paper demonstrate the effectiveness of the approach in providing quantitative estimates that bound the probability of a FP or FN abort determination.
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Myers, Owen D; Sumner, Susan J; Li, Shuzhao; Barnes, Stephen; Du, Xiuxia
2017-09-05
XCMS and MZmine 2 are two widely used software packages for preprocessing untargeted LC/MS metabolomics data. Both construct extracted ion chromatograms (EICs) and detect peaks from the EICs, the first two steps in the data preprocessing workflow. While both packages have performed admirably in peak picking, they also detect a problematic number of false positive EIC peaks and can also fail to detect real EIC peaks. The former and latter translate downstream into spurious and missing compounds and present significant limitations with most existing software packages that preprocess untargeted mass spectrometry metabolomics data. We seek to understand the specific reasons why XCMS and MZmine 2 find the false positive EIC peaks that they do and in what ways they fail to detect real compounds. We investigate differences of EIC construction methods in XCMS and MZmine 2 and find several problems in the XCMS centWave peak detection algorithm which we show are partly responsible for the false positive and false negative compound identifications. In addition, we find a problem with MZmine 2's use of centWave. We hope that a detailed understanding of the XCMS and MZmine 2 algorithms will allow users to work with them more effectively and will also help with future algorithmic development.
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Larsen, C P; Ezligini, F; Hermansen, N O; Kjeldsen-Kragh, J
2005-02-01
Approximately 1 in every 2000 units of platelets is contaminated with bacteria. The BacT/ALERT automated blood culture system can be used to screen platelet concentrates (PCs) for bacterial contamination. Data were collected from May 1998 until May 2004. The number of PCs tested during this period was 36 896, most of which were produced from pools of four buffy-coats. On the day following blood collection or platelet apheresis, a 5-10 ml sample of the PC was aseptically transferred to a BacT/ALERT culture bottle for detection of aerobic bacteria. The sample was monitored for bacterial growth during the entire storage period of the PC (6.5 days). When a positive signal was generated, the culture bottle, the PC and the erythrocyte concentrates were tested for bacterial growth. In order to determine the frequency of false-negative BacT/ALERT signals, 1061 outdated PCs were tested during the period from May 2002 to May 2004. Eighty-eight positive signals were detected by the BacT/ALERT system, of which 12 were interpreted as truly positive. Fourteen signals were interpreted as truly false positive. Thirty-three signals were interpreted to be probably false positive. Two of 1061 outdated units tested positive, and Bacillus spp. and Staphylococcus epidermidis, respectively, were isolated from these PCs. Between 0.03% and 0.12% of the PCs were contaminated with bacteria. BacT/ALERT is an efficient tool for monitoring PCs for bacterial contamination; however, it is important to realize that false-negative results may occur.
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Detection of epileptic seizure in EEG signals using linear least squares preprocessing.
Roshan Zamir, Z
2016-09-01
An epileptic seizure is a transient event of abnormal excessive neuronal discharge in the brain. This unwanted event can be obstructed by detection of electrical changes in the brain that happen before the seizure takes place. The automatic detection of seizures is necessary since the visual screening of EEG recordings is a time consuming task and requires experts to improve the diagnosis. Much of the prior research in detection of seizures has been developed based on artificial neural network, genetic programming, and wavelet transforms. Although the highest achieved accuracy for classification is 100%, there are drawbacks, such as the existence of unbalanced datasets and the lack of investigations in performances consistency. To address these, four linear least squares-based preprocessing models are proposed to extract key features of an EEG signal in order to detect seizures. The first two models are newly developed. The original signal (EEG) is approximated by a sinusoidal curve. Its amplitude is formed by a polynomial function and compared with the predeveloped spline function. Different statistical measures, namely classification accuracy, true positive and negative rates, false positive and negative rates and precision, are utilised to assess the performance of the proposed models. These metrics are derived from confusion matrices obtained from classifiers. Different classifiers are used over the original dataset and the set of extracted features. The proposed models significantly reduce the dimension of the classification problem and the computational time while the classification accuracy is improved in most cases. The first and third models are promising feature extraction methods with the classification accuracy of 100%. Logistic, LazyIB1, LazyIB5, and J48 are the best classifiers. Their true positive and negative rates are 1 while false positive and negative rates are 0 and the corresponding precision values are 1. Numerical results suggest that these models are robust and efficient for detecting epileptic seizure. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
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Automated detection of tuberculosis on sputum smeared slides using stepwise classification
NASA Astrophysics Data System (ADS)
Divekar, Ajay; Pangilinan, Corina; Coetzee, Gerrit; Sondh, Tarlochan; Lure, Fleming Y. M.; Kennedy, Sean
2012-03-01
Routine visual slide screening for identification of tuberculosis (TB) bacilli in stained sputum slides under microscope system is a tedious labor-intensive task and can miss up to 50% of TB. Based on the Shannon cofactor expansion on Boolean function for classification, a stepwise classification (SWC) algorithm is developed to remove different types of false positives, one type at a time, and to increase the detection of TB bacilli at different concentrations. Both bacilli and non-bacilli objects are first analyzed and classified into several different categories including scanty positive, high concentration positive, and several non-bacilli categories: small bright objects, beaded, dim elongated objects, etc. The morphological and contrast features are extracted based on aprior clinical knowledge. The SWC is composed of several individual classifiers. Individual classifier to increase the bacilli counts utilizes an adaptive algorithm based on a microbiologist's statistical heuristic decision process. Individual classifier to reduce false positive is developed through minimization from a binary decision tree to classify different types of true and false positive based on feature vectors. Finally, the detection algorithm is was tested on 102 independent confirmed negative and 74 positive cases. A multi-class task analysis shows high accordance rate for negative, scanty, and high-concentration as 88.24%, 56.00%, and 97.96%, respectively. A binary-class task analysis using a receiver operating characteristics method with the area under the curve (Az) is also utilized to analyze the performance of this detection algorithm, showing the superior detection performance on the high-concentration cases (Az=0.913) and cases mixed with high-concentration and scanty cases (Az=0.878).
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Lucas, Rita; Lopes Dias, João; Cunha, Teresa Margarida
2015-01-01
We aimed to evaluate the added value of diffusion-weighted imaging (DWI) to standard magnetic resonance imaging (MRI) for detecting post-treatment cervical cancer recurrence. The detection accuracy of T2-weighted (T2W) images was compared with that of T2W MRI combined with either dynamic contrast-enhanced (DCE) MRI or DWI. Thirty-eight women with clinically suspected uterine cervical cancer recurrence more than six months after treatment completion were examined with 1.5 Tesla MRI including T2W, DCE, and DWI sequences. Disease was confirmed histologically and correlated with MRI findings. The diagnostic performance of T2W imaging and its combination with either DCE or DWI were analyzed. Sensitivity, positive predictive value, and accuracy were calculated. Thirty-six women had histologically proven recurrence. The accuracy for recurrence detection was 80% with T2W/DCE MRI and 92.1% with T2W/DWI. The addition of DCE sequences did not significantly improve the diagnostic ability of T2W imaging, and this sequence combination misclassified two patients as falsely positive and seven as falsely negative. The T2W/DWI combination revealed a positive predictive value of 100% and only three false negatives. The addition of DWI to T2W sequences considerably improved the diagnostic ability of MRI. Our results support the inclusion of DWI in the initial MRI protocol for the detection of cervical cancer recurrence, leaving DCE sequences as an option for uncertain cases.
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Le, Yali; Chen, Yu; Zhou, Fan; Liu, Guangfu; Huang, Zhanwen; Chen, Yue
2016-10-01
This study compared the diagnostic value of F-fluoride PET-computed tomography (PET-CT) and MRI in skull-base bone erosion in nasopharyngeal carcinoma (NPC) patients. A total of 93 patients with biopsy-confirmed NPC were enrolled, including 68 men and 25 women between 23 and 74 years of age. All patients were evaluated by both F-fluoride PET-CT and MRI, and the interval between the two imaging examinations was less than 20 days. The patients received no treatment either before or between scans. The studies were interpreted by two nuclear medicine physicians or two radiologists with more than 10 years of professional experience who were blinded to both the diagnosis and the results of the other imaging studies. The reference standard was skull-base bone erosion at a 20-week follow-up imaging study. On the basis of the results of the follow-up imaging studies, 52 patients showed skull-base bone erosion. The numbers of true positives, false positives, true negatives, and false negatives with F-fluoride PET-CT were 49, 4, 37, and 3, respectively. The numbers of true positives, false positives, true negatives, and false negatives with MRI were 46, 5, 36, and 6, respectively. The sensitivity, specificity, and crude accuracy of F-fluoride PET-CT were 94.23, 90.24, and 92.47%, respectively; for MRI, these values were 88.46, 87.80, and 88.17%. Of the 52 patients, 43 showed positive findings both on F-fluoride PET-CT and on MRI. Within the patient cohort, F-fluoride PET-CT and MRI detected 178 and 135 bone lesions, respectively. Both F-fluoride PET-CT and MRI have high sensitivity, specificity, and crude accuracy for detecting skull-base bone invasion in patients with NPC. F-fluoride PET-CT detected more lesions than did MRI in the skull-base bone. This suggests that F-fluoride PET-CT has a certain advantage in evaluating the skull-base bone of NPC patients. Combining the two methods could improve the diagnostic accuracy of skull-base bone invasion for NPC.
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Jing, Chang-Wen; Wang, Zhuo; Cao, Hai-Xia; Ma, Rong; Wu, Jian-Zhong
2014-01-01
The aim of the research was to explore a cost effective, fast, easy to perform, and sensitive method for epidermal growth factor receptor (EGFR) mutation testing. High resolution melting analysis (HRM) was introduced to evaluate the efficacy of the analysis for dectecting EGFR mutations in exons 18 to 21 using formalin-fixed paraffin-embedded (FFPE) tissues and plasma free DNA from 120 patients. The total EGFR mutation rate was 37.5% (45/120) detected by direct sequencing. There were 48 mutations in 120 FFPE tissues assessed by HRM. For plasma free DNA, the EGFR mutation rate was 25.8% (31/120). The sensitivity of HRM assays in FFPE samples was 100% by HRM. There was a low false-positive mutation rate but a high false-negative rate in plasma free DNA detected by HRM. Our results show that HRM analysis has the advantage of small tumor sample need. HRM applied with plasma free DNA showed a high false-negative rate but a low false-positive rate. Further research into appropriate methods and analysis needs to be performed before HRM for plasma free DNA could be accepted as an option in diagnostic or screening settings.
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Kielar, Ania Z; Shabana, Wael; Vakili, Maryam; Rubin, Jonathan
2012-10-01
The twinkling artifact is an emerging tool for identifying urinary tract calculi. The purpose of this prospective study was to evaluate the diagnostic accuracy of the twinkling artifact compared to unenhanced computed tomography in detecting urolithasis. After Research Ethics Board approval, 51 patients with flank pain from the emergency department were enrolled between November 2009 and September 2010. Patients received an unenhanced computed tomographic scan with 1.25-mm raw data and reformatted 5-mm axial and 2-mm coronal images. Blinded assessment of the urinary tract was performed with gray-scale and color Doppler interrogation. The number of calculi, location, size, kidney distance from the skin, body mass index of the patient, and sonographic image parameters were recorded. There were 35 right-sided and 38 left-sided renal calculi, 14 right-sided and 21 left-sided ureteric calculi, and 6 bladder calculi (total, 114 calculi). Thirteen patients had no calculi. The average calculus size was 2.6 mm (range, 1-9 mm). There were 6 false-positive and 22 false-negative instances of twinkling artifacts. On gray-scale evaluation looking for an echogenic focus with shadowing, there were 8 false-positive and 40 false-negative findings. The positive predictive value (PPV) of the twinkling artifact for identifying calculi was 94%, and the sensitivity was 83%. The PPV of gray-scale sonographic shadowing was only 64.9%, and the sensitivity was 80.2%. The twinkling artifact has a high PPV for detecting renal and urinary tract calculi. Evaluation for the twinkling artifact is a complementary technique to standard gray-scale shadowing of calculi and improves detection of urolithiasis on sonography.
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Paley, Pamela J; Veljovich, Dan S; Press, Joshua Z; Isacson, Christina; Pizer, Ellen; Shah, Chirag
2016-07-01
The accuracy of sentinel lymph node mapping has been shown in endometrial cancer, but studies to date have primarily focused on cohorts at low risk for nodal involvement. In our practice, we acknowledge the lack of benefit of lymphadenectomy in the low-risk subgroup and omit lymph node removal in these patients. Thus, our aim was to evaluate the feasibility and accuracy of sentinel node mapping in women at sufficient risk for nodal metastasis warranting lymphadenectomy and in whom the potential benefit of avoiding nodal procurement could be realized. To evaluate the detection rate and accuracy of fluorescence-guided sentinel lymph node mapping in endometrial cancer patients undergoing robotic-assisted staging. One hundred twenty-three endometrial cancer patients undergoing sentinel lymph node sentinel node mapping using indocyanine green were prospectively evaluated. Two mL (1.0 mg/mL) of dye were injected into the cervical stroma divided between the 2-3 and 9-10 o'clock positions at the time of uterine manipulator placement. Before hysterectomy, the retroperitoneal spaces were developed and fluorescence imaging was used for sentinel node detection. Identified sentinel nodes were removed and submitted for touch prep intraoperatively, followed by permanent assessment with routine hematoxylin and eosin levels. Patients then underwent hysterectomy, bilateral salpingo-oophorectomy, and completion bilateral pelvic and periaortic lymphadenectomy based on intrauterine risk factors determined intraoperatively (tumor size >2 cm, >50% myometrial invasion, and grade 3 histology). Of 123 patients enrolled, at least 1 sentinel node was detected in 119 (96.7%). Ninety-nine patients (80%) had bilateral pelvic or periaortic sentinel nodes detected. A total of 85 patients met criteria warranting completion lymphadenectomy. In 14 patients (16%) periaortic lymphadenectomy was not feasible, and the mean number of pelvic nodes procured was 13 (6-22). Of the 71 patients undergoing pelvic and periaortic lymphadenectomy, the mean nodal count was 23.2 (8-51). Of patients undergoing lymphadenectomy, 10.6% had lymph node metastasis on final hematoxylin and eosin evaluation. Notably, the sentinel node was the only positive node in 44% of cases. There were no cases in which final pathology of the sentinel node was negative and metastatic disease was detected upon completion lymphadenectomy in the non-sentinel nodes (no false negatives), yielding a sensitivity of 100%. Of the 14 sentinel nodes ultimately found to harbor metastases, 3 were negative on touch prep, yielding a sensitivity of 78.6% for intraoperative detection of sentinel node involvement. In all 3 of the false-negative touch preps, final pathology detected a single micrometastasis (0.24 mm, 1.4 mm, 1.5 mm). As expected, there were no false-positive results, yielding a specificity of 100%. No complications related to sentinel node mapping or allergic reactions to the dye were encountered. Intraoperative sentinel node mapping using fluorescence imaging with indocyanine green in endometrial cancer patients is feasible and yields high detection rates. In our pilot study, sentinel node mapping identified all women with Stage IIIC disease. Low false-negative rates are encouraging, and if confirmed in multi-institutional trials, this approach would be anticipated to reduce the morbidity, operative times, and costs associated with complete pelvic and periaortic lymphadenectomy. Copyright © 2015 Elsevier Inc. All rights reserved.
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Assessment of error rates in acoustic monitoring with the R package monitoR
Katz, Jonathan; Hafner, Sasha D.; Donovan, Therese
2016-01-01
Detecting population-scale reactions to climate change and land-use change may require monitoring many sites for many years, a process that is suited for an automated system. We developed and tested monitoR, an R package for long-term, multi-taxa acoustic monitoring programs. We tested monitoR with two northeastern songbird species: black-throated green warbler (Setophaga virens) and ovenbird (Seiurus aurocapilla). We compared detection results from monitoR in 52 10-minute surveys recorded at 10 sites in Vermont and New York, USA to a subset of songs identified by a human that were of a single song type and had visually identifiable spectrograms (e.g. a signal:noise ratio of at least 10 dB: 166 out of 439 total songs for black-throated green warbler, 502 out of 990 total songs for ovenbird). monitoR’s automated detection process uses a ‘score cutoff’, which is the minimum match needed for an unknown event to be considered a detection and results in a true positive, true negative, false positive or false negative detection. At the chosen score cut-offs, monitoR correctly identified presence for black-throated green warbler and ovenbird in 64% and 72% of the 52 surveys using binary point matching, respectively, and 73% and 72% of the 52 surveys using spectrogram cross-correlation, respectively. Of individual songs, 72% of black-throated green warbler songs and 62% of ovenbird songs were identified by binary point matching. Spectrogram cross-correlation identified 83% of black-throated green warbler songs and 66% of ovenbird songs. False positive rates were for song event detection.
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NASA Astrophysics Data System (ADS)
Mirniaharikandehei, Seyedehnafiseh; Hollingsworth, Alan B.; Patel, Bhavika; Heidari, Morteza; Liu, Hong; Zheng, Bin
2018-05-01
This study aims to investigate the feasibility of identifying a new quantitative imaging marker based on false-positives generated by a computer-aided detection (CAD) scheme to help predict short-term breast cancer risk. An image dataset including four view mammograms acquired from 1044 women was retrospectively assembled. All mammograms were originally interpreted as negative by radiologists. In the next subsequent mammography screening, 402 women were diagnosed with breast cancer and 642 remained negative. An existing CAD scheme was applied ‘as is’ to process each image. From CAD-generated results, four detection features including the total number of (1) initial detection seeds and (2) the final detected false-positive regions, (3) average and (4) sum of detection scores, were computed from each image. Then, by combining the features computed from two bilateral images of left and right breasts from either craniocaudal or mediolateral oblique view, two logistic regression models were trained and tested using a leave-one-case-out cross-validation method to predict the likelihood of each testing case being positive in the next subsequent screening. The new prediction model yielded the maximum prediction accuracy with an area under a ROC curve of AUC = 0.65 ± 0.017 and the maximum adjusted odds ratio of 4.49 with a 95% confidence interval of (2.95, 6.83). The results also showed an increasing trend in the adjusted odds ratio and risk prediction scores (p < 0.01). Thus, this study demonstrated that CAD-generated false-positives might include valuable information, which needs to be further explored for identifying and/or developing more effective imaging markers for predicting short-term breast cancer risk.
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False Negatives for Remote Life Detection on Ocean-Bearing Planets: Lessons from the Early Earth.
Reinhard, Christopher T; Olson, Stephanie L; Schwieterman, Edward W; Lyons, Timothy W
2017-04-01
Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes throughout its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal of work has centered on refining our understanding of false positives for remote life detection, much less attention has been paid to the possibility of false negatives, that is, cryptic biospheres that are widespread and active on a planet's surface but are ultimately undetectable or difficult to detect in the composition of a planet's atmosphere. Here, we summarize recent developments from geochemical proxy records and Earth system models that provide insight into the long-term evolution of the most readily detectable potential biosignature gases on Earth-oxygen (O 2 ), ozone (O 3 ), and methane (CH 4 ). We suggest that the canonical O 2 -CH 4 disequilibrium biosignature would perhaps have been challenging to detect remotely during Earth's ∼4.5-billion-year history and that in general atmospheric O 2 /O 3 levels have been a poor proxy for the presence of Earth's biosphere for all but the last ∼500 million years. We further suggest that detecting atmospheric CH 4 would have been problematic for most of the last ∼2.5 billion years of Earth's history. More broadly, we stress that internal oceanic recycling of biosignature gases will often render surface biospheres on ocean-bearing silicate worlds cryptic, with the implication that the planets most conducive to the development and maintenance of a pervasive biosphere will often be challenging to characterize via conventional atmospheric biosignatures. Key Words: Biosignatures-Oxygen-Methane-Ozone-Exoplanets-Planetary habitability. Astrobiology 17, 287-297.
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False Negatives for Remote Life Detection on Ocean-Bearing Planets: Lessons from the Early Earth
Olson, Stephanie L.; Schwieterman, Edward W.; Lyons, Timothy W.
2017-01-01
Abstract Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes throughout its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal of work has centered on refining our understanding of false positives for remote life detection, much less attention has been paid to the possibility of false negatives, that is, cryptic biospheres that are widespread and active on a planet's surface but are ultimately undetectable or difficult to detect in the composition of a planet's atmosphere. Here, we summarize recent developments from geochemical proxy records and Earth system models that provide insight into the long-term evolution of the most readily detectable potential biosignature gases on Earth—oxygen (O2), ozone (O3), and methane (CH4). We suggest that the canonical O2-CH4 disequilibrium biosignature would perhaps have been challenging to detect remotely during Earth's ∼4.5-billion-year history and that in general atmospheric O2/O3 levels have been a poor proxy for the presence of Earth's biosphere for all but the last ∼500 million years. We further suggest that detecting atmospheric CH4 would have been problematic for most of the last ∼2.5 billion years of Earth's history. More broadly, we stress that internal oceanic recycling of biosignature gases will often render surface biospheres on ocean-bearing silicate worlds cryptic, with the implication that the planets most conducive to the development and maintenance of a pervasive biosphere will often be challenging to characterize via conventional atmospheric biosignatures. Key Words: Biosignatures—Oxygen—Methane—Ozone—Exoplanets—Planetary habitability. Astrobiology 17, 287–297. PMID:28418704
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Amplification of Mitochondrial DNA for detection of Plasmodiumvivax in Balochistan.
Shahwani, Muhammad Naeem; Nisar, Samia; Aleem, Abdul; Panezai, Marina; Afridi, Sarwat; Malik, Shaukat Iqbal
2017-05-01
To access a new step using PCR to amplify the targeted mtDNA sequence for detecting specifically Plasmodium vivax and its co-infections, false positive and false negative results with Plasmodium falciparum. In this study we have standardized a new technical approach in which the target mitochondrial DNA sequence (mtDNA) was amplified by using a PCR technique as a tool to detect Plasmodium spp. Species specific primers were designed to hybridize with cytochrome c oxidase gene of P. vivax (cox I) and P. falciparum (cox III). Two hundred blood samples were collected on the basis of clinical symptoms which were initially examined through microscopic analysis after preparing Giemsa stained thick and thin blood smears. Afterwards genomic DNA was extracted from all samples and was then subjected to PCR amplification by using species specific primers and amplified segments were sequenced for confirmation of results. One-hundred and thirty-two blood samples were detected as positive for malaria by PCR, out of which 64 were found to be positive by PCR and 53 by both microscopy and PCR for P.vivax infection. Nine samples were found to be false negative, one P.vivax mono infection was declared as co infection by PCR and 3 samples identified as having P.falciparum gametes were confirmed as P.vivax by PCR amplification. Sensitivity and specificity were found to be 85% and 92% respectively. Results obtained through PCR method were comparatively better and reliable than microscopy.
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Emergency ultrasound in the acute assessment of haemothorax
Brooks, A; Davies, B; Smethhurst, M; Connolly, J
2004-01-01
Aims: To evaluate thoracic ultrasound for the detection of haemothorax in patients with thoracic trauma against established investigations. Methods: Thoracic ultrasound was performed as an extension of the standard focused assessment with sonography for trauma (FAST) protocol used at the Queen's Medical Centre for the assessment of adult patients with torso trauma. Fluid was sought in both pleural cavities using a hand portable ultrasound system by one of two non-radiologists trained in FAST. Findings were compared against subsequent investigations/procedures performed at the discretion of the attending emergency physician—supine chest radiography, intercostal drain, computed tomography, or thoracotomy. The sensitivity of the technique and the time taken to diagnosis for each investigation were recorded. Results: Sixty one patients, 54 (89%) after blunt trauma, underwent thoracic ultrasound evaluation during the study. Twelve patients had a haemothorax detected by ultrasound and confirmed by computed tomography or by tube thoracostomy. Four haemothoraces detected on ultrasound were not apparent on trauma chest radiography. There were 12 true positives, 48 true negatives, no false positives, and one false negative scan. The sensitivity of ultrasound was 92% and specificity 100% with a positive predictive value of 100% and negative predictive value 98% for the detection of haemothorax after trauma. Conclusions: Emergency ultrasound of the chest performed as part of the primary survey of the traumatised patient can rapidly and accurately diagnose haemothorax and is a valuable tool to augment the immediate clinical assessment of these patients. PMID:14734374
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Use of the Abbott Architect HIV antigen/antibody assay in a low incidence population.
Dubravac, Terry; Gahan, Thomas F; Pentella, Michael A
2013-12-01
With the availability of 4th generation HIV diagnostic tests which are capable of detecting acute infection, Iowa evaluated the 3rd and 4th generation HIV test and compared the performance of these products in a low incidence population. This study was conducted to evaluate the performance of an HIV antigen/antibody combination (4th generation) assay compared to an EIA 3rd generation assay. Over a 4 month period, 2037 specimens submitted for HIV screening were tested by Bio-Rad GS HIV-1/HIV-2 Plus O EIA and the Abbott Architect i1000SR HIV Ag/Ab Combo. The performance characteristics of sensitivity, specificity, positive predictive value and negative predictive value were determined. Of the 2037 specimens tested, there were 13 (0.64%) true positives detected. None of the positive specimens were from patients in the acute phase of infection. The Abbott antigen/antibody combo assay had a sensitivity, specificity, positive-predictive value and negative predictive value of 100%, 99.85%, 81.25%, and 100% respectively. The Bio-Rad EIA assay had a sensitivity, specificity, positive-predictive value and negative predictive value of 100%, 99.80%, 76.47% and 100%, respectively. The EIA had four false positive results which tested negative by the antigen/antibody assay and western blot. In a low-incidence state where early infections are less commonly encountered, the EIA assay and the antigen/antibody assay performed with near equivalency. The antigen/antibody assay had one less false positive result. While no patients were detected in the acute stage of infection, the use of the antigen/antibody assay presents the opportunity to detect an infected patient sooner and prevent transmission to others. Copyright © 2013 Elsevier B.V. All rights reserved.
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McCusker, J J; McCoy, E L; Young, C L; Alamares, R; Hirsch, L S
1984-01-01
The Directigen Group A Strep Test (DGAST), a new rapid method of detecting group A beta-hemolytic streptococci directly from throat swabs, was compared with a traditional culture technique for the detection of group A beta-hemolytic streptococci. Five hundred oropharyngeal swabs from pediatric and adult patients were cultured and then processed by using the DGAST. Of the 144 specimens positive by culture, 131 were DGAST positive (sensitivity, 90.9%). Of the 356 specimens negative by culture, 353 were DGAST negative (specificity, 99.2%). Twelve of the 13 false-negative DGAST results were from pediatric patients. One hundred isolates of non-group A beta-hemolytic streptococci were recovered, primarily groups C, F, and G. The DGAST is easy to perform, rapid, sensitive, and very specific for detection of group A beta-hemolytic streptococci directly from swabs. Supplementing the DGAST with a culture on a 5% sheep blood agar plate would enhance detection of group A beta-hemolytic streptococci, especially in pediatric patients. PMID:6386884
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Role of Urine Drug Testing in the Current Opioid Epidemic.
Mahajan, Gagan
2017-12-01
While the evidence for urine drug testing for patients on chronic opioid therapy is weak, the guidelines created by numerous medical societies and state and federal regulatory agencies recommend that it be included as one of the tools used to monitor patients for compliance with chronic opioid therapy. To get the most comprehensive results, clinicians should order both an immunoassay screen and confirmatory urine drug test. The immunoassay screen, which can be performed as an in-office point-of-care test or as a laboratory-based test, is a cheap and convenient study to order. Limitations of an immunoassay screen, however, include having a high threshold of detectability and only providing qualitative information about a select number of drug classes. Because of these restrictions, clinicians should understand that immunoassay screens have high false-positive and false-negative rates. Despite these limitations, though, the results can assist the clinician with making preliminary treatment decisions. In comparison, a confirmatory urine drug test, which can only be performed as a laboratory-based test, has a lower threshold of detectability and provides both qualitative and quantitative information. A urine drug test's greater degree of specificity allows for a relatively low false-negative and false-positive rate in contrast to an immunoassay screen. Like any other diagnostic test, an immunoassay screen and a confirmatory urine drug test both possess limitations. Clinicians must keep this in mind when interpreting an unexpected test result and consult with their laboratory when in doubt about the meaning of the test result to avoid making erroneous decisions that negatively impact both the patient and clinician.
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Koizumi, Mitsuru; Motegi, Kazuki; Koyama, Masamichi; Terauchi, Takashi; Yuasa, Takeshi; Yonese, Junji
2017-08-01
The computer-assisted diagnostic system for bone scintigraphy (BS) BONENAVI is used to evaluate skeletal metastasis. We investigated its diagnostic performance in prostate cancer patients with and without skeletal metastasis and searched for the problems. An artificial neural network (ANN) value was calculated in 226 prostate cancer patients (124 with skeletal metastasis and 101 without) using BS. Receiver operating characteristic curve analysis was performed and the sensitivity and specificity determined (cutoff ANN = 0.5). Patient's situation at the time of diagnosis of skeletal metastasis, computed tomography (CT) type, extent of disease (EOD), and BS uptake grade were analyzed. False-negative and false-positive results were recorded. BONENAVI showed 82% (102/124) of sensitivity and 83% (84/101) specificity for metastasis detection. There were no significant differences among CT types, although low EOD and faint BS uptake were associated with low ANN values and low sensitivity. Patients showed lower sensitivity during the follow-up period than staging work-up. False-negative lesions were often located in the pelvis or adjacent to it. They comprised not only solitary, faint BS lesions but also overlaying to urinary excretion. BONENAVI with BS has good sensitivity and specificity for detecting prostate cancer's osseous metastasis. Low EOD and faint BS uptake are associated with low sensitivity but not the CT type. Prostate cancer patients likely to have false-negative results during the follow-up period had a solitary lesion in the pelvis with faint BS uptake or lesions overlaying to urinary excretion.
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Follow-up of negative MRI-targeted prostate biopsies: when are we missing cancer?
Gold, Samuel A; Hale, Graham R; Bloom, Jonathan B; Smith, Clayton P; Rayn, Kareem N; Valera, Vladimir; Wood, Bradford J; Choyke, Peter L; Turkbey, Baris; Pinto, Peter A
2018-05-21
Multiparametric magnetic resonance imaging (mpMRI) has improved clinicians' ability to detect clinically significant prostate cancer (csPCa). Combining or fusing these images with the real-time imaging of transrectal ultrasound (TRUS) allows urologists to better sample lesions with a targeted biopsy (Tbx) leading to the detection of greater rates of csPCa and decreased rates of low-risk PCa. In this review, we evaluate the technical aspects of the mpMRI-guided Tbx procedure to identify possible sources of error and provide clinical context to a negative Tbx. A literature search was conducted of possible reasons for false-negative TBx. This includes discussion on false-positive mpMRI findings, termed "PCa mimics," that may incorrectly suggest high likelihood of csPCa as well as errors during Tbx resulting in inexact image fusion or biopsy needle placement. Despite the strong negative predictive value associated with Tbx, concerns of missed disease often remain, especially with MR-visible lesions. This raises questions about what to do next after a negative Tbx result. Potential sources of error can arise from each step in the targeted biopsy process ranging from "PCa mimics" or technical errors during mpMRI acquisition to failure to properly register MRI and TRUS images on a fusion biopsy platform to technical or anatomic limits on needle placement accuracy. A better understanding of these potential pitfalls in the mpMRI-guided Tbx procedure will aid interpretation of a negative Tbx, identify areas for improving technical proficiency, and improve both physician understanding of negative Tbx and patient-management options.
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Antituberculosis IgG Antibodies as a Marker of Active Mycobacterium tuberculosis Disease
Welch, Ryan J.; Lawless, Kathleen M.
2012-01-01
Anti-Mycobacterium tuberculosis IgG antibodies may aid in the diagnosis of active M. tuberculosis disease. We studied whether anti-M. tuberculosis IgG antibodies are elevated in active M. tuberculosis disease and assessed factors contributing to false-positive and -negative results. A retrospective study of 2,150 individuals tested by the QuantiFERON-TB Gold In-Tube (QFT-GIT) assay was conducted at the University of Utah, ARUP Laboratories, November 2008 to December 2010. All samples were tested with the InBios Active TbDetect antituberculosis (anti-TB) IgG antibody assay. Of 1,044 patients with a positive QFT-GIT, 59 (5.7%) were positive for M. tuberculosis antibodies. Fourteen of 1,106 (1.3%) with a negative or indeterminate QFT-GIT were positive for M. tuberculosis antibodies. M. tuberculosis antibody tests were positive in 61.5% with confirmed active M. tuberculosis disease and other mycobacterial infections. Over half of the false-negative M. tuberculosis antibody tests occurred in patients ≥90 years of age. False positives were seen in 12.9% of autoimmune patients. The odds ratio of being positive by the QFT-GIT and the InBios TB IgG assay increased with confirmed M. tuberculosis disease or highly suspected M. tuberculosis disease and was 86.7 (95% confidence interval [CI], 34.4 to 218.5) in these two groups compared to patients negative by both tests. Although anti-M. tuberculosis antibodies can be detected in patients with active M. tuberculosis disease, caution should be used with patients where immunoglobulin levels may be decreased or patients with autoantibodies. PMID:22301692
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Cadieux, Brigitte; Blanchfield, Burke; Smith, James P; Austin, John W
2005-05-01
A simple, rapid, cost-effective in vitro slot blot immunoassay was developed for the detection and quantification of botulinum neurotoxin type E (BoNT/E) in cultures. Culture supernatants of 36 strains of clostridia, including 12 strains of Clostridium botulinum type E, 12 strains of other C. botulinum neurotoxin serotypes, and 12 strains of other clostridial species were tested. Samples containing BoNT/E were detected using affinity-purified polyclonal rabbit antisera prepared against BoNT/E with subsequent detection of secondary antibodies using chemiluminescence. All strains of C. botulinum type E tested positive, while all non C. botulinum type E strains tested negative. The sensitivity of the slot blot immunoassay for detection of BoNT/E was approximately four mouse lethal doses (MLD). The intensity of chemiluminescence was directly correlated with the concentration of BoNT/E up to 128 MLD, allowing quantification of BoNT/E between 4 and 128 MLD. The slot blot immunoassay was compared to the mouse bioassay for detection of BoNT/E using cultures derived from fish samples inoculated with C. botulinum type E, and cultures derived from naturally contaminated environmental samples. A total of 120 primary enrichment cultures derived from fish samples, of which 103 were inoculated with C. botulinum type E, and 17 were uninoculated controls, were assayed. Of the 103 primary enrichment cultures derived from inoculated fish samples, all were positive by mouse bioassay, while 94 were also positive by slot blot immunoassay, resulting in a 7.5% false-negative rate. All 17 primary enrichment cultures derived from the uninoculated fish samples were negative by both mouse bioassay and slot blot immunoassay. A total of twenty-six primary enrichment cultures derived from environmental samples were tested by mouse bioassay and slot blot immunoassay. Of 13 primary enrichment cultures positive by mouse bioassay, 12 were also positive by slot blot immunoassay, resulting in a 3.8% false-negative rate. All 13 primary enrichment cultures that tested negative by mouse bioassay also tested negative by slot blot immunoassay. The slot blot immunoassay could be used routinely as a positive screen for BoNT/E in primary enrichment cultures, and could be used as a replacement for the mouse bioassay for pure cultures.
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Scott, T.W.; Olson, J.G.; Lewis, T.E.; Carpenter, J.W.; Lorenz, L.H.; Lembeck, L.A.; Joseph, S.R.; Pagac, B.B.
1987-01-01
A prospective field study was conducted to determine the sensitivity and specificity of an enzyme immunoassay (EIA) compared to virus isolation in cell culture for the detection of eastern equine encephalomyelitis (EEE) virus in naturally infected mosquitoes. A total of 10,811 adult female Culiseta melanura were collected in light traps during 1985 from four locations in Maryland. Eastern equine encephalomyelitis virus was isolated from 5 of 495 mosquito pools in African green monkey kidney and baby hamster kidney cell cultures. All five virus-infected pools were detected by the EIA, and all 490 uninfected pools were correctly scored as not containing virus. The EIA did not produce false positive or false negative results. Results support the assertion of previous researchers that the antigen detection EIA is a rapid, sensitive, specific, and simple alternative to traditional bioassays for the detection of EEE virus in mosquitoes.
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Underpowered samples, false negatives, and unconscious learning.
Vadillo, Miguel A; Konstantinidis, Emmanouil; Shanks, David R
2016-02-01
The scientific community has witnessed growing concern about the high rate of false positives and unreliable results within the psychological literature, but the harmful impact of false negatives has been largely ignored. False negatives are particularly concerning in research areas where demonstrating the absence of an effect is crucial, such as studies of unconscious or implicit processing. Research on implicit processes seeks evidence of above-chance performance on some implicit behavioral measure at the same time as chance-level performance (that is, a null result) on an explicit measure of awareness. A systematic review of 73 studies of contextual cuing, a popular implicit learning paradigm, involving 181 statistical analyses of awareness tests, reveals how underpowered studies can lead to failure to reject a false null hypothesis. Among the studies that reported sufficient information, the meta-analytic effect size across awareness tests was d z = 0.31 (95 % CI 0.24-0.37), showing that participants' learning in these experiments was conscious. The unusually large number of positive results in this literature cannot be explained by selective publication. Instead, our analyses demonstrate that these tests are typically insensitive and underpowered to detect medium to small, but true, effects in awareness tests. These findings challenge a widespread and theoretically important claim about the extent of unconscious human cognition.
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Li, Zhixi; He, Yifan; Keel, Stuart; Meng, Wei; Chang, Robert T; He, Mingguang
2018-03-02
To assess the performance of a deep learning algorithm for detecting referable glaucomatous optic neuropathy (GON) based on color fundus photographs. A deep learning system for the classification of GON was developed for automated classification of GON on color fundus photographs. We retrospectively included 48 116 fundus photographs for the development and validation of a deep learning algorithm. This study recruited 21 trained ophthalmologists to classify the photographs. Referable GON was defined as vertical cup-to-disc ratio of 0.7 or more and other typical changes of GON. The reference standard was made until 3 graders achieved agreement. A separate validation dataset of 8000 fully gradable fundus photographs was used to assess the performance of this algorithm. The area under receiver operator characteristic curve (AUC) with sensitivity and specificity was applied to evaluate the efficacy of the deep learning algorithm detecting referable GON. In the validation dataset, this deep learning system achieved an AUC of 0.986 with sensitivity of 95.6% and specificity of 92.0%. The most common reasons for false-negative grading (n = 87) were GON with coexisting eye conditions (n = 44 [50.6%]), including pathologic or high myopia (n = 37 [42.6%]), diabetic retinopathy (n = 4 [4.6%]), and age-related macular degeneration (n = 3 [3.4%]). The leading reason for false-positive results (n = 480) was having other eye conditions (n = 458 [95.4%]), mainly including physiologic cupping (n = 267 [55.6%]). Misclassification as false-positive results amidst a normal-appearing fundus occurred in only 22 eyes (4.6%). A deep learning system can detect referable GON with high sensitivity and specificity. Coexistence of high or pathologic myopia is the most common cause resulting in false-negative results. Physiologic cupping and pathologic myopia were the most common reasons for false-positive results. Copyright © 2018 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.
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Bruno, Thiers; Abrahão, Julia
2012-01-01
This study examines the actions taken by operators aimed at preventing and combating information security incidents at a banking organization. The work utilizes the theoretical framework of ergonomics and cognitive psychology. The method is workplace ergonomic analysis. Its focus is directed towards examining the cognitive dimension of the work environment with special attention to the occurrence of correlations between variability in incident frequency and the results of sign detection actions. It categorizes 45,142 operator decisions according to the theory of signal detection (Sternberg, 2000). It analyzes the correlation between incident proportions (indirectly associated with the cognitive efforts demanded from the operator) and operator decisions. The study demonstrated the existence of a positive correlation between incident proportions and false positive decisions (false alarms). However, this correlation could not be observed in relation to decisions of the false-negative type (incorrect rejection).
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Can integrated 18F-FDG PET/MR replace sentinel lymph node resection in malignant melanoma?
Schaarschmidt, Benedikt Michael; Grueneisen, Johannes; Stebner, Vanessa; Klode, Joachim; Stoffels, Ingo; Umutlu, Lale; Schadendorf, Dirk; Heusch, Philipp; Antoch, Gerald; Pöppel, Thorsten Dirk
2018-06-06
To compare the sensitivity and specificity of 18F-fluordesoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT), 18F-FDG PET/magnetic resonance (18F-FDG PET/MR) and 18F-FDG PET/MR including diffusion weighted imaging (DWI) in the detection of sentinel lymph node metastases in patients suffering from malignant melanoma. Fifty-two patients with malignant melanoma (female: n = 30, male: n = 22, mean age 50.5 ± 16.0 years, mean tumor thickness 2.28 ± 1.97 mm) who underwent 18F-FDG PET/CT and subsequent PET/MR & DWI for distant metastasis staging were included in this retrospective study. After hybrid imaging, lymphoscintigraphy including single photon emission computed tomography/CT (SPECT/CT) was performed to identify the sentinel lymph node prior to sentinel lymph node biopsy (SLNB). In a total of 87 sentinel lymph nodes in 64 lymph node basins visible on SPECT/CT, 17 lymph node metastases were detected by histopathology. In separate sessions PET/CT, PET/MR, and PET/MR & DWI were assessed for sentinel lymph node metastases by two independent readers. Discrepant results were resolved in a consensus reading. Sensitivities, specificities, positive predictive values and negative predictive values were calculated with histopathology following SPECT/CT guided SLNB as a reference standard. Compared with histopathology, lymph nodes were true positive in three cases, true negative in 65 cases, false positive in three cases and false negative in 14 cases in PET/CT. PET/MR was true positive in four cases, true negative in 63 cases, false positive in two cases and false negative in 13 cases. Hence, we observed a sensitivity, specificity, positive predictive value and negative predictive value of 17.7, 95.6, 50.0 and 82.3% for PET/CT and 23.5, 96.9, 66.7 and 82.3% for PET/MR. In DWI, 56 sentinel lymph node basins could be analyzed. Here, the additional analysis of DWI led to two additional false positive findings, while the number of true positive findings could not be increased. In conclusion, integrated 18F-FDG PET/MR does not reliably differentiate N-positive from N-negative melanoma patients. Additional DWI does not increase the sensitivity of 18F-FDG PET/MR. Hence, sentinel lymph node biopsy cannot be replaced by 18F-FDG-PE/MR or 18F-FDG-PET/CT.
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Aly, Ibrahim; Taher, Eman E; El Nain, Gehan; El Sayed, Hoda; Mohammed, Faten A; Hamad, Rabab S; Bayoumy, Elsayed M
2018-01-01
Nanotechnology is a promising arena for generating new applications in Medicine. To successfully functionalised nanoparticles for a given biomedical application, a wide range of chemical, physical and biological factors have to be taken into account. Silica-coated nanoparticles, (SiO2NP) exhibit substantial diagnostic activity owing to their large surface to volume ratios and crystallographic surface structure. This work aimed to evaluate the advantage of bioconjugation of SiO2NP with PAb against Toxoplasma lyzate antigen (TLA) as an innovative diagnostic method for human toxoplasmosis. This cross-sectional study included 120 individuals, divided into Group I: 70 patients suspected for Toxoplasma gondii based on the presence of clinical manifestation. Group II: 30 patients harboring other parasites than T. gondii Group III: 20 apparently healthy individuals free from toxoplasmosis and other parasitic infections served as negative control. Detection of circulating Toxoplasma antigen was performed by Sandwich ELISA and Nano-sandwich ELISA on sera and pooled urine of human samples. Using Sandwich ELISA, 10 out of 70 suspected Toxoplasma-infected human serum samples showed false negative and 8 out of 30 of other parasites groups were false positive giving 85.7% sensitivity and 84.0% specificity, while the sensitivity and specificity were 78.6% and 70% respectively in urine samples. Using Nano-Sandwich ELISA, 7 out of 70 suspected Toxoplasma-infected human samples showed false negative results and the sensitivity of the assay was 90.0%, while 4 out of 30 of other parasites groups were false positive giving 92.0% specificity, while the sensitivity and specificity were 82.6% and 80% respectively in urine samples. In conclusion, our data demonstrated that loading SiO2 nanoparticles with pAb increased the sensitivity and specificity of Nano-sandwich ELISA for detection of T.gondii antigens in serum and urine samples, thus active (early) and light infections could be easily detected. Copyright © 2017 Elsevier B.V. All rights reserved.
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Stanzel, Susanne; Pernthaler, Birgit; Schwarz, Thomas; Bjelic-Radisic, Vesna; Kerschbaumer, Stefan; Aigner, Reingard M
2018-06-01
of the study was to demonstrate the diagnostic and prognostic value of SPECT/CT in sentinel lymph node mapping (SLNM) in patients with invasive breast cancer. 114 patients with invasive breast cancer with clinically negative lymph nodes were included in this retrospective study as they were referred for SLNM with 99m Tc-nanocolloid. Planar image acquisition was accomplished in a one-day or two-day protocol depending on the schedule of the surgical procedure. Low dose SPECT/CT was performed after the planar images. The sentinel lymph node biopsy (SLNB) was considered false negative if a primary recurrence developed within 12 months after SLNB in the axilla from which a tumor-free SLN had been removed. Between December 2009 and December 2011, 114 patients (pts.) underwent SLNM with additional SPECT/CT. Planar imaging identified in 109 pts. 139 SLNs, which were tumor-positive in 42 nodes (n = 41 pts.). SPECT/CT identified in 81 pts. 151 additional SLNs, of which 19 were tumor-positive and led to therapy change (axillary lymph node dissection) in 11 pts. (9.6 %). Of overall 61 tumor-positive SLNs (n = 52 pts.) SPECT/CT detected all, whereas planar imaging detected only 42 of 61 ( P < 0.0001). No patient had lymph node metastasis within 12 months after SLNB in the axilla from which a tumor-free SLN had been removed resulting in a false-negative rate of 0 %. The local relapse rate was 1.8 % leading to a 4-year disease-free survival rate of 90 %. Among patients with breast cancer, the use of SPECT/CT-aided SLNM correlated due to a better anatomical localization and identification of planar not visible SLNs with a higher detection rate of SLNs. This led to therapeutic consequences and an excellent false-negative and 4-year disease-free survival rate. Schattauer GmbH.
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Application of data fusion technology based on D-S evidence theory in fire detection
NASA Astrophysics Data System (ADS)
Cai, Zhishan; Chen, Musheng
2015-12-01
Judgment and identification based on single fire characteristic parameter information in fire detection is subject to environmental disturbances, and accordingly its detection performance is limited with the increase of false positive rate and false negative rate. The compound fire detector employs information fusion technology to judge and identify multiple fire characteristic parameters in order to improve the reliability and accuracy of fire detection. The D-S evidence theory is applied to the multi-sensor data-fusion: first normalize the data from all sensors to obtain the normalized basic probability function of the fire occurrence; then conduct the fusion processing using the D-S evidence theory; finally give the judgment results. The results show that the method meets the goal of accurate fire signal identification and increases the accuracy of fire alarm, and therefore is simple and effective.
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E-commerce Review System to Detect False Reviews.
Kolhar, Manjur
2017-08-15
E-commerce sites have been doing profitable business since their induction in high-speed and secured networks. Moreover, they continue to influence consumers through various methods. One of the most effective methods is the e-commerce review rating system, in which consumers provide review ratings for the products used. However, almost all e-commerce review rating systems are unable to provide cumulative review ratings. Furthermore, review ratings are influenced by positive and negative malicious feedback ratings, collectively called false reviews. In this paper, we proposed an e-commerce review system framework developed using the cumulative sum method to detect and remove malicious review ratings.
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Galkin, O Yu; Besarab, A B; Lutsenko, T N
2017-01-01
The goal of this work was to study sensitivity and specificity of the developed ELISA set for the identification of IgG antibodies against Chlamydia trachomatis HSP-60 (using biotinylated tyramine-based signal amplification system). The study was conducted using a panel of characterized sera, as well as two reference ELISA sets of similar purpose. According to the results of ELISA informative value parameters, the ELISA we have developed showed the highest specificity and sensitivity parameters (no false negative or false positive results were registered). In 4 out of 15 intralaboratory panel serum samples initially identified as negative, anti-HSP-60 IgG-antibodies test result in reference ELISA sets upon dilution changed from negative to positive. The nature of titration curves of false negative sera and commercial monoclonal antibodies А57-В9 against C. trachomatis HSP-60 after incubation for 24 h was indicative of the presence of anti-idiotypic antibodies in these samples. Upon sera dilution, idiotypic-anti-idiotypic complexes dissociated, which caused the change of test result. High informative value of the developed ELISA set for identification of IgG antibodies against C. trachomatis HSP-60 has been proven. Anti-idiotypic antibodies possessing C. trachomatis anti-HSP-60 activity and being one of the causes of false negative results of the relevant ELISA-based tests have been identified in blood sera of individuals infected with chlamydial genitourinary infection agents.
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Performance of Momguard, a new non-invasive prenatal testing protocol developed in Korea.
Lee, Mi-Young; Cho, Dae-Yeon; Won, Hye-Sung; Hwang, Ah Reum; Jeong, Bada; Kim, Jihun; Oh, Mijin
2015-09-01
To evaluate the performance of Momguard, non-invasive prenatal test (NIPT) for detecting trisomy (T) 21, T18, T13, and sex-chromosome abnormalities recently developed in Korea. This preliminary study formed part of a large prospective cohort study conducted at Asan Medical Center, Seoul, Korea. Only pregnant women who underwent both NIPT and confirmatory karyotyping were included in this study. NIPT results were compared with those of karyotype analyses. Among 93 eligible cases, NIPT results could not be obtained in one case due to a low fetal cell-free DNA fraction. Based on NIPT, eight cases of fetal aneuploidies, including T21 (n=5), T18 (n=2), and T13 (n=1), were identified. For T21 and T18, the sensitivity and specificity of NIPT were both 100%, with a false-positive and false-negative rate of 0% and a positive-predictive value of 100%. One patient classified as having intermediate risk for T13 by NIPT was confirmed to have T13 by karyotyping, and there were no false-negative cases. No cases of sex-chromosome anomalies were detected by NIPT or karyotyping during the study period. Momguard is a reliable screening tool for detecting T21 and T18. For T13 and sex-chromosome anomalies, further prospective studies are necessary to confirm its utility.
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Zhang, He; Hou, Chang; Zhou, Zhi; Zhang, Hao; Zhou, Gen; Zhang, Gui
2014-01-01
The diagnostic performance of 64-detector computed tomographic angiography (CTA) for detection of small intracranial aneurysms (SIAs) was evaluated. In this prospective study, 112 consecutive patients underwent 64-detector CTA before volume-rendering rotation digital subtraction angiography (VR-RDSA) or surgery. VR-RDSA or intraoperative findings or both were used as the gold standards. The accuracy, sensitivity, specificity, and positive predictive values (PPV) and negative predictive values (NPV), as measures to detect or rule out SIAs, were determined by patient-based and aneurysm size-based evaluations. The reference standard methods revealed 84 small aneurysms in 71 patients. The results of patient-based 64-detector CTA evaluation for SIAs were: accuracy, 98.2%; sensitivity, 98.6%; specificity, 97.6%; PPV, 98.6%; and NPV, 97.6%. The aneurysm-based evaluation results were: accuracy, 96.8%; sensitivity, 97.6%; specificity, 95.1%; PPV, 97.6%; and NPV, 95.1%. Two false-positive and two false-negative findings for aneurysms <3 mm in size occurred in the 64-detector CTA analysis. The diagnostic performance of 64-detector CTA did not improve much compared with 16-detector CTA for detecting SIAs, especially for very small aneurysms. VR-RDSA is still necessary for patients with a history of subarachnoid hemorrhage if the CTA findings are negative. Copyright © 2012 by the American Society of Neuroimaging.
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Savant, Deepika; Bajaj, Jaya; Gimenez, Cecilia; Rafael, Oana C; Mirzamani, Neda; Chau, Karen; Klein, Melissa; Das, Kasturi
2017-01-01
Urine cytology is the most frequently utilized test to detect urothelial cancer. Secondary bladder neoplasms need to be recognized as this impacts patient management. We report our experience on nonurothelial malignancies (NUM) detected in urine cytology over a 10-year period. A 10-year retrospective search for patients with biopsy-proven NUM to the urothelial tract yielded 25 urine samples from 14 patients. Two cytopathologists blinded to the original cytology diagnosis reviewed the cytology and histology slides. The incidence, cytomorphologic features, diagnostic accuracy, factors influencing the diagnostic accuracy, and clinical impact of the cytology result were studied. The incidence of NUM was <1%. The male:female ratio was 1.3. An abnormality was detected in 60% of the cases; however, in only 4% of the cases, a primary site was identified accurately. Of the false negatives, 96% was deemed as sampling errors and 4% was interpretational. Patient management was not impacted in any of the false-negative cases due to concurrent or past tissue diagnosis. Colon cancer was the most frequent secondary tumor. Sampling error attributed to the false-negative results. Necrosis and dirty background was often associated with metastatic lesions from colon. Obtaining history of a primary tumor elsewhere was a key factor in diagnosis of a metastatic lesion. Hematopoietic malignancies remain to be a diagnostic challenge. Cytospin preparations were superior for evaluating nuclear detail and background material as opposed to monolayer (Thinprep) technology. Diagnostic accuracy was improved by obtaining immunohistochemistry. Diagn. Cytopathol. 2016. © 2016 Wiley Periodicals, Inc. Diagn. Cytopathol. 2017;45:22-28. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
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Tousseyn, Simon; Dupont, Patrick; Goffin, Karolien; Sunaert, Stefan; Van Paesschen, Wim
2014-01-01
There is currently a lack of knowledge about electroencephalography (EEG)-functional magnetic resonance imaging (fMRI) specificity. Our aim was to define sensitivity and specificity of blood oxygen level dependent (BOLD) responses to interictal epileptic spikes during EEG-fMRI for detecting the ictal onset zone (IOZ). We studied 21 refractory focal epilepsy patients who had a well-defined IOZ after a full presurgical evaluation and interictal spikes during EEG-fMRI. Areas of spike-related BOLD changes overlapping the IOZ in patients were considered as true positives; if no overlap was found, they were treated as false-negatives. Matched healthy case-controls had undergone similar EEG-fMRI in order to determine true-negative and false-positive fractions. The spike-related regressor of the patient was used in the design matrix of the healthy case-control. Suprathreshold BOLD changes in the brain of controls were considered as false positives, absence of these changes as true negatives. Sensitivity and specificity were calculated for different statistical thresholds at the voxel level combined with different cluster size thresholds and represented in receiver operating characteristic (ROC)-curves. Additionally, we calculated the ROC-curves based on the cluster containing the maximal significant activation. We achieved a combination of 100% specificity and 62% sensitivity, using a Z-threshold in the interval 3.4–3.5 and cluster size threshold of 350 voxels. We could obtain higher sensitivity at the expense of specificity. Similar performance was found when using the cluster containing the maximal significant activation. Our data provide a guideline for different EEG-fMRI settings with their respective sensitivity and specificity for detecting the IOZ. The unique cluster containing the maximal significant BOLD activation was a sensitive and specific marker of the IOZ. PMID:25101049
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Supporting diagnosis of attention-deficit hyperactive disorder with novelty detection.
Lee, Hyoung-Joo; Cho, Sungzoon; Shin, Min-Sup
2008-03-01
Computerized continuous performance test (CPT) is a widely used diagnostic tool for attention-deficit hyperactivity disorder (ADHD). It measures the number of correctly detected stimuli as well as response times. Typically, when calculating a cut-off score for discriminating between normal and abnormal, only the normal children's data are collected. Then the average and standard deviation of each measure or variable is computed. If any of variables is larger than 2 sigma above the average, that child is diagnosed as abnormal. We will call this approach as "T-score 70" classifier. However, its performance has a lot to be desired due to a high false negative error. In order to improve the classification accuracy we propose to use novelty detection approaches for supporting ADHD diagnosis. Novelty detection is a model building framework where a classifier is constructed using only one class of training data and a new input pattern is classified according to its similarity to the training data. A total of eight novelty detectors are introduced and applied to our ADHD datasets collected from two modes of tests, visual and auditory. They are evaluated and compared with the T-score model on validation datasets in terms of false positive and negative error rates, and area under receiver operating characteristics curve (AuROC). Experimental results show that the cut-off score of 70 is suboptimal which leads to a low false positive error but a very high false negative error. A few novelty detectors such as Parzen density estimators yield much more balanced classification performances. Moreover, most novelty detectors outperform the T-score method for most age groups statistically with a significance level of 1% in terms of AuROC. In particular, we recommend the Parzen and Gaussian density estimators, kernel principal component analysis, one-class support vector machine, and K-means clustering novelty detector which can improve upon the T-score method on average by at least 30% for the visual test and 40% for the auditory test. In addition, their performances are relatively stable over various parameter values as long as they are within reasonable ranges. The proposed novelty detection approaches can replace the T-score method which has been considered the "gold standard" for supporting ADHD diagnosis. Furthermore, they can be applied to other psychological tests where only normal data are available.
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Samanipour, Saer; Baz-Lomba, Jose A; Alygizakis, Nikiforos A; Reid, Malcolm J; Thomaidis, Nikolaos S; Thomas, Kevin V
2017-06-09
LC-HR-QTOF-MS recently has become a commonly used approach for the analysis of complex samples. However, identification of small organic molecules in complex samples with the highest level of confidence is a challenging task. Here we report on the implementation of a two stage algorithm for LC-HR-QTOF-MS datasets. We compared the performances of the two stage algorithm, implemented via NIVA_MZ_Analyzer™, with two commonly used approaches (i.e. feature detection and XIC peak picking, implemented via UNIFI by Waters and TASQ by Bruker, respectively) for the suspect analysis of four influent wastewater samples. We first evaluated the cross platform compatibility of LC-HR-QTOF-MS datasets generated via instruments from two different manufacturers (i.e. Waters and Bruker). Our data showed that with an appropriate spectral weighting function the spectra recorded by the two tested instruments are comparable for our analytes. As a consequence, we were able to perform full spectral comparison between the data generated via the two studied instruments. Four extracts of wastewater influent were analyzed for 89 analytes, thus 356 detection cases. The analytes were divided into 158 detection cases of artificial suspect analytes (i.e. verified by target analysis) and 198 true suspects. The two stage algorithm resulted in a zero rate of false positive detection, based on the artificial suspect analytes while producing a rate of false negative detection of 0.12. For the conventional approaches, the rates of false positive detection varied between 0.06 for UNIFI and 0.15 for TASQ. The rates of false negative detection for these methods ranged between 0.07 for TASQ and 0.09 for UNIFI. The effect of background signal complexity on the two stage algorithm was evaluated through the generation of a synthetic signal. We further discuss the boundaries of applicability of the two stage algorithm. The importance of background knowledge and experience in evaluating the reliability of results during the suspect screening was evaluated. Copyright © 2017 Elsevier B.V. All rights reserved.
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Qualitative PCR method for Roundup Ready soybean: interlaboratory study.
Kodama, Takashi; Kasahara, Masaki; Minegishi, Yasutaka; Futo, Satoshi; Sawada, Chihiro; Watai, Masatoshi; Akiyama, Hiroshi; Teshima, Reiko; Kurosawa, Yasunori; Furui, Satoshi; Hino, Akihiro; Kitta, Kazumi
2011-01-01
Quantitative and qualitative methods based on PCR have been developed for genetically modified organisms (GMO). Interlaboratory studies were previously conducted for GMO quantitative methods; in this study, an interlaboratory study was conducted for a qualitative method for a GM soybean, Roundup Ready soy (RR soy), with primer pairs designed for the quantitative method of RR soy studied previously. Fourteen laboratories in Japan participated. Each participant extracted DNA from 1.0 g each of the soy samples containing 0, 0.05, and 0.10% of RR soy, and performed PCR with primer pairs for an internal control gene (Le1) and RR soy followed by agarose gel electrophoresis. The PCR product amplified in this PCR system for Le1 was detected from all samples. The sensitivity, specificity, and false-negative and false-positive rates of the method were obtained from the results of RR soy detection. False-negative rates at the level of 0.05 and 0.10% of the RR soy samples were 6.0 and 2.3%, respectively, revealing that the LOD of the method was somewhat below 0.10%. The current study demonstrated that the qualitative method would be practical for monitoring the labeling system of GM soy in kernel lots.
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2014-02-26
set of anomaly detection rules 62 I.-R. Chen et al. / Ad Hoc Networks 19 (2014) 59–74 Author’s personal copy including the interval rule (for...deficiencies in anomaly detection (e.g., imperfection of rules) by a false negative probability (PHfn) of misidentifying an unhealthy node as a...multimedia servers, Multimedia Syst. 8 (2) (2000) 83–91. [53] R. Mitchell, I.R. Chen, Adaptive intrusion detection for unmanned aircraft systems based on
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Ramos, Ana Carolina; Carvalhaes, Cecília Godoy; Cordeiro-Moura, Jhonatha Rodrigo; Rockstroh, Anna Carolina; Machado, Antonia Maria Oliveira; Gales, Ana Cristina
2016-07-01
In this study, we evaluated the influence of distinct bacterial growth media on detection of carbapenemase hydrolysis by matrix-assisted laser desorption ionization-time of flight mass spectrometry. False-negative results were observed for OXA-25-, OXA-26-, and OXA-72-producing Acinetobacter baumannii isolates grown on MacConkey agar medium. The other culture media showed 100% sensitivity and 100% specificity for detecting carbapenemase. Copyright © 2016, American Society for Microbiology. All Rights Reserved.
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Occupancy Modeling for Improved Accuracy and Understanding of Pathogen Prevalence and Dynamics
Colvin, Michael E.; Peterson, James T.; Kent, Michael L.; Schreck, Carl B.
2015-01-01
Most pathogen detection tests are imperfect, with a sensitivity < 100%, thereby resulting in the potential for a false negative, where a pathogen is present but not detected. False negatives in a sample inflate the number of non-detections, negatively biasing estimates of pathogen prevalence. Histological examination of tissues as a diagnostic test can be advantageous as multiple pathogens can be examined and providing important information on associated pathological changes to the host. However, it is usually less sensitive than molecular or microbiological tests for specific pathogens. Our study objectives were to 1) develop a hierarchical occupancy model to examine pathogen prevalence in spring Chinook salmon Oncorhynchus tshawytscha and their distribution among host tissues 2) use the model to estimate pathogen-specific test sensitivities and infection rates, and 3) illustrate the effect of using replicate within host sampling on sample sizes required to detect a pathogen. We examined histological sections of replicate tissue samples from spring Chinook salmon O. tshawytscha collected after spawning for common pathogens seen in this population: Apophallus/echinostome metacercariae, Parvicapsula minibicornis, Nanophyetus salmincola/ metacercariae, and Renibacterium salmoninarum. A hierarchical occupancy model was developed to estimate pathogen and tissue-specific test sensitivities and unbiased estimation of host- and organ-level infection rates. Model estimated sensitivities and host- and organ-level infections rates varied among pathogens and model estimated infection rate was higher than prevalence unadjusted for test sensitivity, confirming that prevalence unadjusted for test sensitivity was negatively biased. The modeling approach provided an analytical approach for using hierarchically structured pathogen detection data from lower sensitivity diagnostic tests, such as histology, to obtain unbiased pathogen prevalence estimates with associated uncertainties. Accounting for test sensitivity using within host replicate samples also required fewer individual fish to be sampled. This approach is useful for evaluating pathogen or microbe community dynamics when test sensitivity is <100%. PMID:25738709
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Occupancy modeling for improved accuracy and understanding of pathogen prevalence and dynamics
Colvin, Michael E.; Peterson, James T.; Kent, Michael L.; Schreck, Carl B.
2015-01-01
Most pathogen detection tests are imperfect, with a sensitivity < 100%, thereby resulting in the potential for a false negative, where a pathogen is present but not detected. False negatives in a sample inflate the number of non-detections, negatively biasing estimates of pathogen prevalence. Histological examination of tissues as a diagnostic test can be advantageous as multiple pathogens can be examined and providing important information on associated pathological changes to the host. However, it is usually less sensitive than molecular or microbiological tests for specific pathogens. Our study objectives were to 1) develop a hierarchical occupancy model to examine pathogen prevalence in spring Chinook salmonOncorhynchus tshawytscha and their distribution among host tissues 2) use the model to estimate pathogen-specific test sensitivities and infection rates, and 3) illustrate the effect of using replicate within host sampling on sample sizes required to detect a pathogen. We examined histological sections of replicate tissue samples from spring Chinook salmon O. tshawytscha collected after spawning for common pathogens seen in this population:Apophallus/echinostome metacercariae, Parvicapsula minibicornis, Nanophyetus salmincola/metacercariae, and Renibacterium salmoninarum. A hierarchical occupancy model was developed to estimate pathogen and tissue-specific test sensitivities and unbiased estimation of host- and organ-level infection rates. Model estimated sensitivities and host- and organ-level infections rates varied among pathogens and model estimated infection rate was higher than prevalence unadjusted for test sensitivity, confirming that prevalence unadjusted for test sensitivity was negatively biased. The modeling approach provided an analytical approach for using hierarchically structured pathogen detection data from lower sensitivity diagnostic tests, such as histology, to obtain unbiased pathogen prevalence estimates with associated uncertainties. Accounting for test sensitivity using within host replicate samples also required fewer individual fish to be sampled. This approach is useful for evaluating pathogen or microbe community dynamics when test sensitivity is <100%.
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External Quality Assessment for Avian Influenza A (H7N9) Virus Detection Using Armored RNA
Sun, Yu; Jia, Tingting; Sun, Yanli; Han, Yanxi; Wang, Lunan; Zhang, Rui; Zhang, Kuo; Lin, Guigao; Xie, Jiehong
2013-01-01
An external quality assessment (EQA) program for the molecular detection of avian influenza A (H7N9) virus was implemented by the National Center for Clinical Laboratories (NCCL) of China in June 2013. Virus-like particles (VLPs) that contained full-length RNA sequences of the hemagglutinin (HA), neuraminidase (NA), matrix protein (MP), and nucleoprotein (NP) genes from the H7N9 virus (armored RNAs) were constructed. The EQA panel, comprising 6 samples with different concentrations of armored RNAs positive for H7N9 viruses and four H7N9-negative samples (including one sample positive for only the MP gene of the H7N9 virus), was distributed to 79 laboratories in China that carry out the molecular detection of H7N9 viruses. The overall performances of the data sets were classified according to the results for the H7 and N9 genes. Consequently, we received 80 data sets (one participating group provided two sets of results) which were generated using commercial (n = 60) or in-house (n = 17) reverse transcription-quantitative PCR (qRT-PCR) kits and a commercial assay that employed isothermal amplification method (n = 3). The results revealed that the majority (82.5%) of the data sets correctly identified the H7N9 virus, while 17.5% of the data sets needed improvements in their diagnostic capabilities. These “improvable” data sets were derived mostly from false-negative results for the N9 gene at relatively low concentrations. The false-negative rate was 5.6%, and the false-positive rate was 0.6%. In addition, we observed varied diagnostic capabilities between the different commercially available kits and the in-house-developed assays, with the assay manufactured by BioPerfectus Technologies (Jiangsu, China) performing better than the others. Overall, the majority of laboratories have reliable diagnostic capacities for the detection of H7N9 virus. PMID:24088846
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External quality assessment for Avian Influenza A (H7N9) Virus detection using armored RNA.
Sun, Yu; Jia, Tingting; Sun, Yanli; Han, Yanxi; Wang, Lunan; Zhang, Rui; Zhang, Kuo; Lin, Guigao; Xie, Jiehong; Li, Jinming
2013-12-01
An external quality assessment (EQA) program for the molecular detection of avian influenza A (H7N9) virus was implemented by the National Center for Clinical Laboratories (NCCL) of China in June 2013. Virus-like particles (VLPs) that contained full-length RNA sequences of the hemagglutinin (HA), neuraminidase (NA), matrix protein (MP), and nucleoprotein (NP) genes from the H7N9 virus (armored RNAs) were constructed. The EQA panel, comprising 6 samples with different concentrations of armored RNAs positive for H7N9 viruses and four H7N9-negative samples (including one sample positive for only the MP gene of the H7N9 virus), was distributed to 79 laboratories in China that carry out the molecular detection of H7N9 viruses. The overall performances of the data sets were classified according to the results for the H7 and N9 genes. Consequently, we received 80 data sets (one participating group provided two sets of results) which were generated using commercial (n = 60) or in-house (n = 17) reverse transcription-quantitative PCR (qRT-PCR) kits and a commercial assay that employed isothermal amplification method (n = 3). The results revealed that the majority (82.5%) of the data sets correctly identified the H7N9 virus, while 17.5% of the data sets needed improvements in their diagnostic capabilities. These "improvable" data sets were derived mostly from false-negative results for the N9 gene at relatively low concentrations. The false-negative rate was 5.6%, and the false-positive rate was 0.6%. In addition, we observed varied diagnostic capabilities between the different commercially available kits and the in-house-developed assays, with the assay manufactured by BioPerfectus Technologies (Jiangsu, China) performing better than the others. Overall, the majority of laboratories have reliable diagnostic capacities for the detection of H7N9 virus.
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Should bedside sonography be used first to diagnose pneumothorax secondary to blunt trauma?
Donmez, Halil; Tokmak, Turgut Tursem; Yildirim, Afra; Buyukoglan, Hakan; Ozturk, Mehmet; Yaşar Ayaz, Umit; Mavili, Ertugrul
2012-01-01
BACKGROUND.: Our purpose was to evaluate the effectiveness of bedside sonography (US) in the detection of pneumothorax secondary to blunt thoracic trauma. METHODS.: In this prospective study, 240 hemithoraces of 120 consecutive patients with multiple trauma were evaluated with chest radiographs (CXR) and bedside thoracic US for the diagnosis of pneumothorax. CT examinations were performed in 68 patients. Fifty-two patients who did not undergo CT examinations were excluded from the study. US examinations were performed independently at bedside by two radiologists who were not informed about CXR and CT findings. CXRs were interpreted by two radiologists who were unaware of the US and CT results. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of CXR and US were calculated. RESULTS.: One hundred thirty-six hemithoraces were assessed in 68 patients. A total of 35 pneumothoraces were detected in 33 patients. On US, the diagnosis of pneumothorax was correct in 32 hemithoraces. In 98 hemithoraces without pneumothorax, US was normal. With US examination, there were three false-positive and three false-negative results. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of US were 91.4%, 97%, 91.4%, 97%, and 97%, respectively. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of CXR were 82.7%, 89.7%, 68.5%, 95%, and 89.5%, respectively. CONCLUSIONS.: Bedside thoracic US is an accurate method that can be used in trauma patients instead of CXR for the detection of pneumothorax. Copyright © 2012 Wiley Periodicals, Inc.
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Bortcosh, William; Siedner, Mark; Carroll, Ryan W.
2018-01-01
OBJECTIVE Diagnosis of bacterial meningitis often requires cytometry, chemistry and/or microbiologic culture capabilities. Unfortunately, laboratory resources in low-resource settings (LRS) often lack the capacity to perform these studies. We sought to determine whether the presence of white blood cells in CSF detected by commercially available urine reagent strips could aid in the diagnosis of bacterial meningitis. METHODS We searched PubMed for studies published between 1980 and 2016 that investigated the use of urine reagent strips to identify cerebrospinal fluid (CSF) pleocytosis. We assessed studies in any language that enrolled subjects who underwent lumbar puncture and had cerebrospinal fluid testing by both standard laboratory assays and urine reagent strips. We abstracted true-positive, false-negative, false-positive and true-negative counts for each study using a diagnostic threshold of ≥10 white blood cells per microlitre for suspected bacterial meningitis and performed mixed regression modelling with random effects to estimate pooled diagnostic accuracy across studies. RESULTS Our search returned 13 studies including 2235 participants. Urine reagent strips detected CSF pleocytosis with a pooled sensitivity of 92% (95% CI: 84–96), a pooled specificity of 98% (95% CI: 94–99) and a negative predictive value of 99% when the bacterial meningitis prevalence is 10%. CONCLUSIONS Urine reagent strips could provide a rapid and accurate tool to detect CSF pleocytosis, which, if negative, can be used to exclude diagnosis of bacterial meningitis in settings without laboratory infrastructure. Further investigation of the diagnostic value of using protein, glucose and bacteria components of these strips is warranted. PMID:28627004
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Accurate mobile malware detection and classification in the cloud.
Wang, Xiaolei; Yang, Yuexiang; Zeng, Yingzhi
2015-01-01
As the dominator of the Smartphone operating system market, consequently android has attracted the attention of s malware authors and researcher alike. The number of types of android malware is increasing rapidly regardless of the considerable number of proposed malware analysis systems. In this paper, by taking advantages of low false-positive rate of misuse detection and the ability of anomaly detection to detect zero-day malware, we propose a novel hybrid detection system based on a new open-source framework CuckooDroid, which enables the use of Cuckoo Sandbox's features to analyze Android malware through dynamic and static analysis. Our proposed system mainly consists of two parts: anomaly detection engine performing abnormal apps detection through dynamic analysis; signature detection engine performing known malware detection and classification with the combination of static and dynamic analysis. We evaluate our system using 5560 malware samples and 6000 benign samples. Experiments show that our anomaly detection engine with dynamic analysis is capable of detecting zero-day malware with a low false negative rate (1.16 %) and acceptable false positive rate (1.30 %); it is worth noting that our signature detection engine with hybrid analysis can accurately classify malware samples with an average positive rate 98.94 %. Considering the intensive computing resources required by the static and dynamic analysis, our proposed detection system should be deployed off-device, such as in the Cloud. The app store markets and the ordinary users can access our detection system for malware detection through cloud service.
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Pennick, Kate E; McKnight, Christy A; Patterson, Jon S; Latimer, Kenneth S; Maes, Roger K; Wise, Annabel G; Kiupel, Matti
2012-03-01
Immunohistochemistry (IHC) and in situ hybridization (ISH) can be used either to detect or to differentiate between Eastern equine encephalitis virus (EEEV) and West Nile virus (WNV) within formalin-fixed, paraffin-embedded (FFPE) brain tissue of horses. To compare the diagnostic sensitivity and specificity of ISH and IHC, FFPE brain tissue from 20 EEEV-positive horses and 16 WNV-positive horses were tested with both EEEV and WNV oligoprobes and EEEV- and WNV-specific antibodies. Reverse transcription polymerase chain reaction (RT-PCR) for detection of EEEV and WNV was used as the gold standard to confirm infection. All horses that tested positive for EEEV by RT-PCR also tested positive by IHC and ISH, except for 1 case that was false-negative by ISH. In contrast, all horses that tested positive for WNV by RT-PCR tested negative by IHC and only 2 horses tested positive by ISH. No false-positives were detected with either method for both viruses. Both IHC and ISH are highly specific and sensitive diagnostic methods to detect EEEV in equine FFPE brain tissues, although neither appear effective for the diagnosis of WNV in equine neurologic cases.
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Bacterial contamination of platelet components not detected by BacT/ALERT®.
Abela, M A; Fenning, S; Maguire, K A; Morris, K G
2018-02-01
To investigate the possible causes for false negative results in BacT/ALERT ® 3D Signature System despite bacterial contamination of platelet units. The Northern Ireland Blood Transfusion Service (NIBTS) routinely extends platelet component shelf life to 7 days. Components are sampled and screened for bacterial contamination using an automated microbial detection system, the BacT/ALERT ® 3D Signature System. We report on three platelet components with confirmed bacterial contamination, which represent false negative BacT/ALERT ® results and near-miss serious adverse events. NIBTS protocols for risk reduction of bacterial contamination of platelet components are described. The methodology for bacterial detection using BacT/ALERT ® is outlined. Laboratory tests, relevant patient details and relevant follow-up information are analysed. In all three cases, Staphylococcus aureus was isolated from the platelet residue and confirmed on terminal sub-culture using BacT/ALERT ® . In two cases, S. aureus with similar genetic makeup was isolated from the donors. Risk reduction measures for bacterial contamination of platelet components are not always effective. Automated bacterial culture detection does not eliminate the risk of bacterial contamination. Visual inspection of platelet components prior to release, issue and administration remains an important last line of defence. © 2017 British Blood Transfusion Society.
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Jia, Tingting; Zhang, Lei; Wang, Guojing; Zhang, Rui; Zhang, Kuo; Lin, Guigao; Xie, Jiehong; Wang, Lunan; Li, Jinming
2015-01-01
In recent years, nucleic acid tests for detection of measles virus RNA have been widely applied in laboratories belonging to the measles surveillance system of China. An external quality assessment program was established by the National Center for Clinical Laboratories to evaluate the performance of nucleic acid tests for measles virus. The external quality assessment panel, which consisted of 10 specimens, was prepared using armored RNAs, complex of noninfectious MS2 bacteriophage coat proteins encapsulated RNA of measles virus, as measles virus surrogate controls. Conserved sequences amplified from a circulating measles virus strain or from a vaccine strain were encapsulated into these armored RNAs. Forty-one participating laboratories from 15 provinces, municipalities, or autonomous regions that currently conduct molecular detection of measles virus enrolled in the external quality assessment program, including 40 measles surveillance system laboratories and one diagnostic reagent manufacturer. Forty laboratories used commercial reverse transcription-quantitative PCR kits, with only one laboratory applying a conventional PCR method developed in-house. The results indicated that most of the participants (38/41, 92.7%) were able to accurately detect the panel with 100% sensitivity and 100% specificity. Although a wide range of commercially available kits for nucleic acid extraction and reverse transcription polymerase chain reaction were used by the participants, only two false-negative results and one false-positive result were generated; these were generated by three separate laboratories. Both false-negative results were obtained with tests performed on specimens with the lowest concentration (1.2 × 104 genomic equivalents/mL). In addition, all 18 participants from Beijing achieved 100% sensitivity and 100% specificity. Overall, we conclude that the majority of the laboratories evaluated have reliable diagnostic capacities for the detection of measles virus. PMID:26244795
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Zhang, Dong; Sun, Yu; Jia, Tingting; Zhang, Lei; Wang, Guojing; Zhang, Rui; Zhang, Kuo; Lin, Guigao; Xie, Jiehong; Wang, Lunan; Li, Jinming
2015-01-01
In recent years, nucleic acid tests for detection of measles virus RNA have been widely applied in laboratories belonging to the measles surveillance system of China. An external quality assessment program was established by the National Center for Clinical Laboratories to evaluate the performance of nucleic acid tests for measles virus. The external quality assessment panel, which consisted of 10 specimens, was prepared using armored RNAs, complex of noninfectious MS2 bacteriophage coat proteins encapsulated RNA of measles virus, as measles virus surrogate controls. Conserved sequences amplified from a circulating measles virus strain or from a vaccine strain were encapsulated into these armored RNAs. Forty-one participating laboratories from 15 provinces, municipalities, or autonomous regions that currently conduct molecular detection of measles virus enrolled in the external quality assessment program, including 40 measles surveillance system laboratories and one diagnostic reagent manufacturer. Forty laboratories used commercial reverse transcription-quantitative PCR kits, with only one laboratory applying a conventional PCR method developed in-house. The results indicated that most of the participants (38/41, 92.7%) were able to accurately detect the panel with 100% sensitivity and 100% specificity. Although a wide range of commercially available kits for nucleic acid extraction and reverse transcription polymerase chain reaction were used by the participants, only two false-negative results and one false-positive result were generated; these were generated by three separate laboratories. Both false-negative results were obtained with tests performed on specimens with the lowest concentration (1.2 × 104 genomic equivalents/mL). In addition, all 18 participants from Beijing achieved 100% sensitivity and 100% specificity. Overall, we conclude that the majority of the laboratories evaluated have reliable diagnostic capacities for the detection of measles virus.
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A novel seizure detection algorithm informed by hidden Markov model event states
NASA Astrophysics Data System (ADS)
Baldassano, Steven; Wulsin, Drausin; Ung, Hoameng; Blevins, Tyler; Brown, Mesha-Gay; Fox, Emily; Litt, Brian
2016-06-01
Objective. Recently the FDA approved the first responsive, closed-loop intracranial device to treat epilepsy. Because these devices must respond within seconds of seizure onset and not miss events, they are tuned to have high sensitivity, leading to frequent false positive stimulations and decreased battery life. In this work, we propose a more robust seizure detection model. Approach. We use a Bayesian nonparametric Markov switching process to parse intracranial EEG (iEEG) data into distinct dynamic event states. Each event state is then modeled as a multidimensional Gaussian distribution to allow for predictive state assignment. By detecting event states highly specific for seizure onset zones, the method can identify precise regions of iEEG data associated with the transition to seizure activity, reducing false positive detections associated with interictal bursts. The seizure detection algorithm was translated to a real-time application and validated in a small pilot study using 391 days of continuous iEEG data from two dogs with naturally occurring, multifocal epilepsy. A feature-based seizure detector modeled after the NeuroPace RNS System was developed as a control. Main results. Our novel seizure detection method demonstrated an improvement in false negative rate (0/55 seizures missed versus 2/55 seizures missed) as well as a significantly reduced false positive rate (0.0012 h versus 0.058 h-1). All seizures were detected an average of 12.1 ± 6.9 s before the onset of unequivocal epileptic activity (unequivocal epileptic onset (UEO)). Significance. This algorithm represents a computationally inexpensive, individualized, real-time detection method suitable for implantable antiepileptic devices that may considerably reduce false positive rate relative to current industry standards.
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Screening for urinary tract infection with the Sysmex UF-1000i urine flow cytometer.
Broeren, Maarten A C; Bahçeci, Semiha; Vader, Huib L; Arents, Niek L A
2011-03-01
The diagnosis of urinary tract infection (UTI) by urine culture is time-consuming and can produce up to 60 to 80% negative results. Fast screening methods that can reduce the necessity for urine cultures will have a large impact on overall turnaround time and laboratory economics. We have evaluated the detection of bacteria and leukocytes by a new urine analyzer, the UF-1000i, to identify negative urine samples that can be excluded from urine culture. In total, 1,577 urine samples were analyzed and compared to urine culture. Urine culture showed growth of ≥10(3) CFU/ml in 939 samples (60%). Receiver operating characteristics (ROC) curves and ROC decision plots were been prepared at three different gold standard definitions of a negative urine culture: no growth, growth of bacteria at <10(4) CFU/ml, and growth of bacteria at <10(5) CFU/ml. Also, the reduction in urine cultures and the percentage of false negatives were calculated. At the most stringent gold standard definition of no growth, a chosen sensitivity of 95% resulted in a cutoff value of 26 bacteria/μl, a specificity of 43% and a reduction in urine cultures of only 20%, of which 14% were false negatives. However, at a gold standard definition of <10(5) CFU/ml and a sensitivity of 95%, the UF-1000i cutoff value was 230 bacteria/μl, the specificity was 80%, and the reduction in urine cultures was 52%, of which 0.3% were false negatives. The applicability of the UF-1000i to screen for negative urine samples strongly depends on population characteristics and the definition of a negative urine culture. In our setting, however, the low workload savings and the high percentage of false-negative results do not warrant the UF-1000i to be used as a screening analyzer.
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NASA Astrophysics Data System (ADS)
Inomata, Teppei; Kimura, Kouji; Hagiwara, Masafumi
Studies for video surveillance applications for preventing various crimes such as stealing and violence have become a hot topic. This paper proposes a new video surveillance system that can detect suspicious behaviors such as a car break-in and vandalization in an open space parking, and that is based on image processing. The proposed system has the following features: it 1)deals time series data flow, 2)recognizes “human elemental actions” using statistic features, and 3)detects suspicious behavior using Subspace method and AdaBoost. We conducted the experiments to test the performance of the proposed system using open space parking scenes. As a result, we obtained about 10.0% for false positive rate, and about 4.6% for false negative rate.
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Ranadive, Nikhil; Kunene, Simon; Darteh, Sarah; Ntshalintshali, Nyasatu; Nhlabathi, Nomcebo; Dlamini, Nomcebo; Chitundu, Stanley; Saini, Manik; Murphy, Maxwell; Soble, Adam; Schwartz, Alanna; Greenhouse, Bryan
2017-01-01
Abstract Background. The performance of Plasmodium falciparum–specific histidine-rich protein 2–based rapid diagnostic tests (RDTs) to evaluate suspected malaria in low-endemicity settings has not been well characterized. Methods. Using dried blood spot samples from patients with suspected malaria at 37 health facilities from 2012 to 2014 in the low-endemicity country of Swaziland, we investigated the diagnostic accuracy of histidine-rich protein 2–based RDTs using qualitative polymerase chain reaction (PCR) (nested PCR targeting the cytochrome b gene) and quantitative PCR as reference standards. To explore reasons for false-negative and/or false-positive results, we used pfhrp2/3-specific PCR and logistic regression analyses of potentially associated epidemiological factors. Results. From 1353 patients, 93.0% of RDT-positive (n = 185) and 31.2% of RDT-negative samples (n = 340) were available and selected for testing. Compared with nested PCR, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of RDTs were 51.7%, 94.1%, 67.3%, and 89.1%, respectively. After exclusion of samples with parasite densities <100/μL, which accounted for 75.7% of false-negative results and 33.3% of PCR-detectable infections, the sensitivity, specificity, PPV, and NPV were 78.8%, 93.7%, 62.3%, and 97.1%. Deletions of pfhrp2 were not detected. False-positivity was more likely during the second year and was not associated with demographics, recent malaria, health facility testing characteristics, or potential DNA degradation. Conclusions. In the low-transmission setting of Swaziland, we demonstrated low sensitivity of RDT for malaria diagnosis, owing to an unexpectedly high proportion of low-density infection among symptomatic subjects. The PPV was also low, requiring further investigation. A more accurate point-of-care diagnostic may be needed to support malaria elimination efforts. PMID:28369268
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Ranadive, Nikhil; Kunene, Simon; Darteh, Sarah; Ntshalintshali, Nyasatu; Nhlabathi, Nomcebo; Dlamini, Nomcebo; Chitundu, Stanley; Saini, Manik; Murphy, Maxwell; Soble, Adam; Schwartz, Alanna; Greenhouse, Bryan; Hsiang, Michelle S
2017-05-01
The performance of Plasmodium falciparum-specific histidine-rich protein 2-based rapid diagnostic tests (RDTs) to evaluate suspected malaria in low-endemicity settings has not been well characterized. Using dried blood spot samples from patients with suspected malaria at 37 health facilities from 2012 to 2014 in the low-endemicity country of Swaziland, we investigated the diagnostic accuracy of histidine-rich protein 2-based RDTs using qualitative polymerase chain reaction (PCR) (nested PCR targeting the cytochrome b gene) and quantitative PCR as reference standards. To explore reasons for false-negative and/or false-positive results, we used pfhrp2/3-specific PCR and logistic regression analyses of potentially associated epidemiological factors. From 1353 patients, 93.0% of RDT-positive (n = 185) and 31.2% of RDT-negative samples (n = 340) were available and selected for testing. Compared with nested PCR, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of RDTs were 51.7%, 94.1%, 67.3%, and 89.1%, respectively. After exclusion of samples with parasite densities <100/μL, which accounted for 75.7% of false-negative results and 33.3% of PCR-detectable infections, the sensitivity, specificity, PPV, and NPV were 78.8%, 93.7%, 62.3%, and 97.1%. Deletions of pfhrp2 were not detected. False-positivity was more likely during the second year and was not associated with demographics, recent malaria, health facility testing characteristics, or potential DNA degradation. In the low-transmission setting of Swaziland, we demonstrated low sensitivity of RDT for malaria diagnosis, owing to an unexpectedly high proportion of low-density infection among symptomatic subjects. The PPV was also low, requiring further investigation. A more accurate point-of-care diagnostic may be needed to support malaria elimination efforts. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America.
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New optical method for enhanced detection of colon cancer by capsule endoscopy
NASA Astrophysics Data System (ADS)
Ankri
Equally Contributed , Rinat; Peretz, Dolev; Motiei, Menachem; Sella-Tavor, Osnat; Popovtzer, Rachela2013-09-01
PillCam®COLON capsule endoscopy (CE), a non-invasive diagnostic tool of the digestive tract, has dramatically changed the diagnostic approach and has become an attractive alternative to the conventional colonoscopy for early detection of colorectal cancer. However, despite the significant progress and non-invasive detection capability, studies have shown that its sensitivity and specificity is lower than that of conventional colonoscopy. This work presents a new optical detection method, specifically tailored to colon cancer detection and based on the well-known optical properties of immune-conjugated gold nanorods (GNRs). We show, on a colon cancer model implanted in a chick chorioallantoic membrane (CAM), that this detection method enables conclusive differentiation between cancerous and normal tissues, where neither the distance between the light source and the intestinal wall, nor the background signal, affects the monitored signal. This optical method, which can easily be integrated in CE, is expected to reduce false positive and false negative results and improve identification of tumors and micro metastases.
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Computer-aided diagnosis of contrast-enhanced spectral mammography: A feasibility study.
Patel, Bhavika K; Ranjbar, Sara; Wu, Teresa; Pockaj, Barbara A; Li, Jing; Zhang, Nan; Lobbes, Mark; Zhang, Bin; Mitchell, J Ross
2018-01-01
To evaluate whether the use of a computer-aided diagnosis-contrast-enhanced spectral mammography (CAD-CESM) tool can further increase the diagnostic performance of CESM compared with that of experienced radiologists. This IRB-approved retrospective study analyzed 50 lesions described on CESM from August 2014 to December 2015. Histopathologic analyses, used as the criterion standard, revealed 24 benign and 26 malignant lesions. An expert breast radiologist manually outlined lesion boundaries on the different views. A set of morphologic and textural features were then extracted from the low-energy and recombined images. Machine-learning algorithms with feature selection were used along with statistical analysis to reduce, select, and combine features. Selected features were then used to construct a predictive model using a support vector machine (SVM) classification method in a leave-one-out-cross-validation approach. The classification performance was compared against the diagnostic predictions of 2 breast radiologists with access to the same CESM cases. Based on the SVM classification, CAD-CESM correctly identified 45 of 50 lesions in the cohort, resulting in an overall accuracy of 90%. The detection rate for the malignant group was 88% (3 false-negative cases) and 92% for the benign group (2 false-positive cases). Compared with the model, radiologist 1 had an overall accuracy of 78% and a detection rate of 92% (2 false-negative cases) for the malignant group and 62% (10 false-positive cases) for the benign group. Radiologist 2 had an overall accuracy of 86% and a detection rate of 100% for the malignant group and 71% (8 false-positive cases) for the benign group. The results of our feasibility study suggest that a CAD-CESM tool can provide complementary information to radiologists, mainly by reducing the number of false-positive findings. Copyright © 2017 Elsevier B.V. All rights reserved.
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Hill, William Allen; Randolph, Mildred M; Mandrell, Timothy D
2009-07-01
We determined the sensitivity of perianal tape impressions to detect Syphacia spp. in rats and mice. We evaluated 300 rat and 200 mouse perianal impressions over 9 wk. Pinworm-positive perianal tape impressions from animals with worm burdens at necropsy were considered as true positives. Conversely, pinworm-negative perianal tape impressions from animals with worm burdens were considered false negatives. The sensitivity of perianal tape impressions for detecting Syphacia muris infections in rats was 100%, and for detecting Syphacia obvelata in mice was 85.5%. Intermittent shedding of Syphacia obvelata ova is the most probable explanation for the decreased sensitivity rate we observed in mice. We urge caution in use of perianal tape impressions alone for Syphacia spp. screening in sentinel mice and rats.
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Chhabra, Harleen; Sowmya, Selvaraj; Sreeraj, Vanteemar S; Kalmady, Sunil V; Shivakumar, Venkataram; Amaresha, Anekal C; Narayanaswamy, Janardhanan C; Venkatasubramanian, Ganesan
2016-12-01
Auditory hallucinations constitute an important symptom component in 70-80% of schizophrenia patients. These hallucinations are proposed to occur due to an imbalance between perceptual expectation and external input, resulting in attachment of meaning to abstract noises; signal detection theory has been proposed to explain these phenomena. In this study, we describe the development of an auditory signal detection task using a carefully chosen set of English words that could be tested successfully in schizophrenia patients coming from varying linguistic, cultural and social backgrounds. Schizophrenia patients with significant auditory hallucinations (N=15) and healthy controls (N=15) performed the auditory signal detection task wherein they were instructed to differentiate between a 5-s burst of plain white noise and voiced-noise. The analysis showed that false alarms (p=0.02), discriminability index (p=0.001) and decision bias (p=0.004) were significantly different between the two groups. There was a significant negative correlation between false alarm rate and decision bias. These findings extend further support for impaired perceptual expectation system in schizophrenia patients. Copyright © 2016 Elsevier B.V. All rights reserved.
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Deducing the Milky Way's Massive Cluster Population
NASA Astrophysics Data System (ADS)
Hanson, M. M.; Popescu, B.; Larsen, S. S.; Ivanov, V. D.
2010-11-01
Recent near-infrared surveys of the galactic plane have been used to identify new massive cluster candidates. Follow up study indicates about half are not true, gravitationally-bound clusters. These false positives are created by high density fields of unassociated stars, often due to a sight-line of reduced extinction. What is not so easy to estimate is the number of false negatives, clusters which exist but are not currently being detected by our surveys. In order to derive critical characteristics of the Milky Way's massive cluster population, such as cluster mass function and cluster lifetimes, one must be able to estimate the characteristics of these false negatives. Our group has taken on the daunting task of attempting such an estimate by first creating the stellar cluster imaging simulation program, MASSCLEAN. I will present our preliminary models and methods for deriving the biases of current searches.
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Optimization and validation of CEDIA drugs of abuse immunoassay tests in serum on Hitachi 912.
Kirschbaum, Katrin M; Musshoff, Frank; Schmithausen, Ricarda; Stockhausen, Sarah; Madea, Burkhard
2011-10-10
Due to sensitive limits of detection of chromatographic methods and low limit values regarding the screening of drugs under the terms of impairment in safe driving (§ 24a StVG, Street Traffic Law in Germany), preliminary immunoassay (IA) tests should be able to detect also low concentrations of legal and illegal drugs in serum in forensic cases. False-negatives should be avoided, the rate of false-positive samples should be low due to cost and time. An optimization of IA cutoff values and a validation of the assay is required for each laboratory. In a retrospective study results for serum samples containing amphetamine, methylenedioxy derivatives, cannabinoids, benzodiazepines, cocaine (metabolites), methadone and opiates obtained with CEDIA drugs of abuse reagents on a Hitachi 912 autoanalyzer were compared with quantitative results of chromatographic methods (gas or liquid chromatography coupled with mass spectrometry (GC/MS or LC/MS)). Firstly sensitivity, specificity, positive and negative predictive values and overall misclassification rates were evaluated by contingency tables and compared to ROC-analyses and Youden-Indices. Secondly ideal cutoffs were statistically calculated on the basis of sensitivity and specificity as decisive statistical criteria with focus on a high sensitivity (low rates of false-negatives), i.e. using the Youden-Index. Immunoassay (IA) and confirmatory results were available for 3014 blood samples. Sensitivity was 90% or more for nearly all analytes: amphetamines (IA cutoff 9.5 ng/ml), methylenedioxy derivatives (IA cutoff 5.5 ng/ml), cannabinoids (IA cutoff 14.5 ng/ml), benzodiazepines (IA cutoff >0 ng/ml). Test of opiates showed a sensitivity of 86% for a IA cutoff value of >0 ng/ml. Values for specificity ranged between 33% (methadone, IA cutoff 10 ng/ml) and 90% (cocaine, IA cutoff 20 ng/ml). Lower cutoff values as recommended by ROC analyses were chosen for most tests to decrease the rate of false-negatives. Analyses enabled the definition of cutoff values with good values for sensitivity. Small rates of false-positives can be accepted in forensic cases. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.
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Clinical experience with (/sup 111/ In) indium chloride scanning in inflammatory diseases
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dayem, H.M.; Breen, J.; Leslie, E.V.
1978-05-01
Forty-eight patients were scanned with /sup 111/In-chloride in an attempt to identify the cause of fever. Fifteen true positive scans, 30 true negatives, and 3 false negatives were found. Of the 15 true positives, 7 cases of abdominal or pelvic abscess, and 8 cases of alcoholic hepatitis were detected. The 3 false negatives included: (1) an abscess in the anterior abdominal wall; (2) an abscess in the right upper quadrant at the site of a necrotic gallbladder; and (3) a tuberculous abscess of the lumbar spine. Examples from the different categories, pitfalls in interpretation and advantages and disadvantages of scanningmore » with /sup 111/In-chloride will be presented. These studies indicate that /sup 111/In-chloride is a safe, reliable scanning agent for abscesses below the diaphragm especially in patients who cannot undergo adequate bowel preparation.« less
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Multilayer Statistical Intrusion Detection in Wireless Networks
NASA Astrophysics Data System (ADS)
Hamdi, Mohamed; Meddeb-Makhlouf, Amel; Boudriga, Noureddine
2008-12-01
The rapid proliferation of mobile applications and services has introduced new vulnerabilities that do not exist in fixed wired networks. Traditional security mechanisms, such as access control and encryption, turn out to be inefficient in modern wireless networks. Given the shortcomings of the protection mechanisms, an important research focuses in intrusion detection systems (IDSs). This paper proposes a multilayer statistical intrusion detection framework for wireless networks. The architecture is adequate to wireless networks because the underlying detection models rely on radio parameters and traffic models. Accurate correlation between radio and traffic anomalies allows enhancing the efficiency of the IDS. A radio signal fingerprinting technique based on the maximal overlap discrete wavelet transform (MODWT) is developed. Moreover, a geometric clustering algorithm is presented. Depending on the characteristics of the fingerprinting technique, the clustering algorithm permits to control the false positive and false negative rates. Finally, simulation experiments have been carried out to validate the proposed IDS.
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Zahradnik, Celine; Kolm, Claudia; Martzy, Roland; Mach, Robert L; Krska, Rudolf; Farnleitner, Andreas H; Brunner, Kurt
2014-11-01
In 2003 the European Commission introduced a 0.9% threshold for food and feed products containing genetically modified organism (GMO)-derived components. For commodities containing GMO contents higher than this threshold, labelling is mandatory. To provide a DNA-based rapid and simple detection method suitable for high-throughput screening of GMOs, several isothermal amplification approaches for the 35S promoter were tested: strand displacement amplification, nicking-enzyme amplification reaction, rolling circle amplification, loop-mediated isothermal amplification (LAMP) and helicase-dependent amplification (HDA). The assays developed were tested for specificity in order to distinguish between samples containing genetically modified (GM) maize and non-GM maize. For those assays capable of this discrimination, tests were performed to determine the lower limit of detection. A false-negative rate was determined to rule out whether GMO-positive samples were incorrectly classified as GMO-negative. A robustness test was performed to show reliable detection independent from the instrument used for amplification. The analysis of three GM maize lines showed that only LAMP and HDA were able to differentiate between the GMOs MON810, NK603, and Bt11 and non-GM maize. Furthermore, with the HDA assay it was possible to realize a detection limit as low as 0.5%. A false-negative rate of only 5% for 1% GM maize for all three maize lines shows that HDA has the potential to be used as an alternative strategy for the detection of transgenic maize. All results obtained with the LAMP and HDA assays were compared with the results obtained with a previously reported real-time PCR assay for the 35S promoter in transgenic maize. This study presents two new screening assays for detection of the 35S promoter in transgenic maize by applying the isothermal amplification approaches HDA and LAMP.
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Sampling naturally contaminated broiler carcasses for Salmonella by three different methods
USDA-ARS?s Scientific Manuscript database
Postchill neck skin (NS) maceration and whole carcass rinsing (WCR) are frequently used methods to detect salmonellae from commercially processed broilers. These are practical, nondestructive methods, but they are insensitive and may result in frequent false negatives (20 to 40%). NS samples only ...
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Boufana, Belgees; Umhang, Gérald; Qiu, Jiamin; Chen, Xingwang; Lahmar, Samia; Boué, Franck; Jenkins, David; Craig, Philip
2013-01-01
To investigate echinococcosis in co-endemic regions, three polymerase chain reaction (PCR) assays based on the amplification of a fragment within the NADH dehydrogenase subunit 1 (ND1) mitochondrial gene were optimized for the detection of Echinococcus shiquicus, Echinococcus granulosus G1, and Echinococcus multilocularis DNA derived from parasite tissue or canid fecal samples. Specificity using parasite tissue-derived DNA was found to be 100% except for E. shiquicus primers that faintly detected E. equinus DNA. Sensitivity of the three assays for DNA detection was between 2 and 10 pg. Ethanol precipitation of negative PCR fecal samples was used to eliminate false negatives and served to increase sensitivity as exemplified by an increase in detection from 0% to 89% of E. shiquicus coproDNA using necropsy-positive fox samples. PMID:23438764
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Ray, Laura B.; Sockeel, Stéphane; Soon, Melissa; Bore, Arnaud; Myhr, Ayako; Stojanoski, Bobby; Cusack, Rhodri; Owen, Adrian M.; Doyon, Julien; Fogel, Stuart M.
2015-01-01
A spindle detection method was developed that: (1) extracts the signal of interest (i.e., spindle-related phasic changes in sigma) relative to ongoing “background” sigma activity using complex demodulation, (2) accounts for variations of spindle characteristics across the night, scalp derivations and between individuals, and (3) employs a minimum number of sometimes arbitrary, user-defined parameters. Complex demodulation was used to extract instantaneous power in the spindle band. To account for intra- and inter-individual differences, the signal was z-score transformed using a 60 s sliding window, per channel, over the course of the recording. Spindle events were detected with a z-score threshold corresponding to a low probability (e.g., 99th percentile). Spindle characteristics, such as amplitude, duration and oscillatory frequency, were derived for each individual spindle following detection, which permits spindles to be subsequently and flexibly categorized as slow or fast spindles from a single detection pass. Spindles were automatically detected in 15 young healthy subjects. Two experts manually identified spindles from C3 during Stage 2 sleep, from each recording; one employing conventional guidelines, and the other, identifying spindles with the aid of a sigma (11–16 Hz) filtered channel. These spindles were then compared between raters and to the automated detection to identify the presence of true positives, true negatives, false positives and false negatives. This method of automated spindle detection resolves or avoids many of the limitations that complicate automated spindle detection, and performs well compared to a group of non-experts, and importantly, has good external validity with respect to the extant literature in terms of the characteristics of automatically detected spindles. PMID:26441604
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Human versus automation in responding to failures: an expected-value analysis
NASA Technical Reports Server (NTRS)
Sheridan, T. B.; Parasuraman, R.
2000-01-01
A simple analytical criterion is provided for deciding whether a human or automation is best for a failure detection task. The method is based on expected-value decision theory in much the same way as is signal detection. It requires specification of the probabilities of misses (false negatives) and false alarms (false positives) for both human and automation being considered, as well as factors independent of the choice--namely, costs and benefits of incorrect and correct decisions as well as the prior probability of failure. The method can also serve as a basis for comparing different modes of automation. Some limiting cases of application are discussed, as are some decision criteria other than expected value. Actual or potential applications include the design and evaluation of any system in which either humans or automation are being considered.
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Skaane, Per; Kshirsagar, Ashwini; Hofvind, Solveig; Jahr, Gunnar; Castellino, Ronald A
2012-04-01
Double reading improves the cancer detection rate in mammography screening. Single reading with computer-aided detection (CAD) has been considered to be an alternative to double reading. Little is known about the potential benefit of CAD in breast cancer screening with double reading. To compare prospective independent double reading of screen-film (SFM) and full-field digital (FFDM) mammography in population-based screening with retrospective standalone CAD performance on the baseline mammograms of the screen-detected cancers and subsequent cancers diagnosed during the follow-up period. The study had ethics committee approval. A 5-point rating scale for probability of cancer was used for 23,923 (SFM = 16,983; FFDM = 6940) screening mammograms. Of 208 evaluable cancers, 104 were screen-detected and 104 were subsequent (44 interval and 60 next screening round) cancers. Baseline mammograms of subsequent cancers were retrospectively classified in consensus without information about cancer location, histology, or CAD prompting as normal, non-specific minimal signs, significant minimal signs, and false-negatives. The baseline mammograms of the screen-detected cancers and subsequent cancers were evaluated by CAD. Significant minimal signs and false-negatives were considered 'actionable' and potentially diagnosable if correctly prompted by CAD. CAD correctly marked 94% (98/104) of the baseline mammograms of the screen-detected cancers (SFM = 95% [61/64]; FFDM = 93% [37/40]), including 96% (23/24) of those with discordant interpretations. Considering only those baseline examinations of subsequent cancers prospectively interpreted as normal and retrospectively categorized as 'actionable', CAD input at baseline screening had the potential to increase the cancer detection rate from 0.43% to 0.51% (P = 0.13); and to increase cancer detection by 16% ([104 + 17]/104) and decrease interval cancers by 20% (from 44 to 35). CAD may have the potential to increase cancer detection by up to 16%, and to reduce the number of interval cancers by up to 20% in SFM and FFDM screening programs using independent double reading with consensus review. The influence of true- and false-positive CAD marks on decision-making can, however, only be evaluated in a prospective clinical study.
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[How to manage vertigo in adult?
Vuong Chaney, Hella; Rohmer, Dominique; Charpiot, Anne
2017-11-01
The interrogation and the clinical examination are critical in the research of vertigo etiology. In the context of vertigo, the vital emergencies are of neurological and vascular origins. It is therefore necessary to be able to identify them quickly and simply. Vertigo is a symptom to relieve and the cause is to be diagnosed. Careful questioning combined with neurological examination, nystagmus study, Halmagyi test and skew deviation search are more reliable than imaging in the first 48hours to detect a stroke. There are 12% false negatives in cerebral MRI and 74% false negative in cerebral CT-scan in the first 48hours of an ischemic stroke. Labyrinth emergencies are infectious labyrinthitis, perilymphatic fistula and aeroembolism of the vestibule. Copyright © 2017 Elsevier Masson SAS. All rights reserved.
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Knobloch, O; Pelz, F; Wick, U; Nelson, D L; Zoll, B
1993-03-01
In order to test whether the direct molecular diagnostic approach for fragile X mental retardation (Martin-Bell syndrome, MBS) really makes diagnosis of this disease more precise, we evaluated the results of direct diagnosis in 40 German families at risk together with the results of an earlier study with closely linked flanking markers in the same families. Of 84 men analysed, 43 showed clinical signs. In 39 of these affected men the disease could be confirmed by direct diagnosis. Compared to cytogenetic data, one man was false negative and two were false positive. Two men, whose status could not be determined by means of RFLP data, proved to be normal transmitting males (NTMs). However, the possibility of being an NTM had to be rejected in one case on RFLP data. Fragile X syndrome could be confirmed in 10 of the 13 women with clinical signs. Compared to cytogenetic data there were three cases of false negative results and one of false positive. All 36 obligate carrier women were detected by the direct approach. In addition, 22 women were newly identified as normal transmitting females (NTFs), among them one woman who could not be identified by cytogenetic means or by analysis with closely linked markers. These findings are discussed in view of the relative reliability of the three diagnostic approaches to MBS. Special attention is drawn to the significance of false negative and false positive results in direct diagnosis.
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Accuracy and reliability of forensic latent fingerprint decisions
Ulery, Bradford T.; Hicklin, R. Austin; Buscaglia, JoAnn; Roberts, Maria Antonia
2011-01-01
The interpretation of forensic fingerprint evidence relies on the expertise of latent print examiners. The National Research Council of the National Academies and the legal and forensic sciences communities have called for research to measure the accuracy and reliability of latent print examiners’ decisions, a challenging and complex problem in need of systematic analysis. Our research is focused on the development of empirical approaches to studying this problem. Here, we report on the first large-scale study of the accuracy and reliability of latent print examiners’ decisions, in which 169 latent print examiners each compared approximately 100 pairs of latent and exemplar fingerprints from a pool of 744 pairs. The fingerprints were selected to include a range of attributes and quality encountered in forensic casework, and to be comparable to searches of an automated fingerprint identification system containing more than 58 million subjects. This study evaluated examiners on key decision points in the fingerprint examination process; procedures used operationally include additional safeguards designed to minimize errors. Five examiners made false positive errors for an overall false positive rate of 0.1%. Eighty-five percent of examiners made at least one false negative error for an overall false negative rate of 7.5%. Independent examination of the same comparisons by different participants (analogous to blind verification) was found to detect all false positive errors and the majority of false negative errors in this study. Examiners frequently differed on whether fingerprints were suitable for reaching a conclusion. PMID:21518906
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Accuracy and reliability of forensic latent fingerprint decisions.
Ulery, Bradford T; Hicklin, R Austin; Buscaglia, Joann; Roberts, Maria Antonia
2011-05-10
The interpretation of forensic fingerprint evidence relies on the expertise of latent print examiners. The National Research Council of the National Academies and the legal and forensic sciences communities have called for research to measure the accuracy and reliability of latent print examiners' decisions, a challenging and complex problem in need of systematic analysis. Our research is focused on the development of empirical approaches to studying this problem. Here, we report on the first large-scale study of the accuracy and reliability of latent print examiners' decisions, in which 169 latent print examiners each compared approximately 100 pairs of latent and exemplar fingerprints from a pool of 744 pairs. The fingerprints were selected to include a range of attributes and quality encountered in forensic casework, and to be comparable to searches of an automated fingerprint identification system containing more than 58 million subjects. This study evaluated examiners on key decision points in the fingerprint examination process; procedures used operationally include additional safeguards designed to minimize errors. Five examiners made false positive errors for an overall false positive rate of 0.1%. Eighty-five percent of examiners made at least one false negative error for an overall false negative rate of 7.5%. Independent examination of the same comparisons by different participants (analogous to blind verification) was found to detect all false positive errors and the majority of false negative errors in this study. Examiners frequently differed on whether fingerprints were suitable for reaching a conclusion.
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USDA-ARS?s Scientific Manuscript database
Ractopamine HCl was fed to sheep at 0 (Z), 0.001 (L), 0.01 (M), or 0.1 (H) mg/kg of diet (n = 4 per level, 0.5 kg of feed/day) for seven consecutive days and urine was collected daily about ~16 h post exposure. On-site lateral flow assays were able to reliably (0% false negatives) detect 20 ng of r...
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Chee, Y C
1983-01-01
'Total antinuclear antibody' (ANF) is detected by the fluorescent antinuclear antibody technique which is a screening test, positive in 99% of systemic lupus erythematosus (SLE) sera. The LE factor (positive in 75% of SLE sera), like the anti-DNA antibody, is an antinuclear antibody but directed against DNA-histone. ANF-negative SLE is a clinical entity with absence of these antibodies. A false negative ANF, in the presence of high titre anti-DNA antibody and/or LE cells, is illustrated in two cases of SLE. Postulated mechanisms for this phenomenon are interference in ANF detection by rheumatoid factor, and the prozone effect on the immunofluorescent tests.
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Quantitative polymerase chain reaction (QPCR) can be used as a rapid method for detecting fecal indicator bacteria. Because false negative results can be caused by PCR inhibitors that co-extract with the DNA samples, an internal amplification control (IAC) should be run with eac...
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Overnight incubation of entire broiler carcass for increased detection of Salmonella
USDA-ARS?s Scientific Manuscript database
Introduction Broiler carcasses are generally sampled for presence of human pathogens such as Salmonella by whole carcass rinse and enrichment of a portion of the rinse. This may leave firmly attached cells out of the analysis potentially leading to false negative results. Purpose The objective of ...
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Automatic detection of apical roots in oral radiographs
NASA Astrophysics Data System (ADS)
Wu, Yi; Xie, Fangfang; Yang, Jie; Cheng, Erkang; Megalooikonomou, Vasileios; Ling, Haibin
2012-03-01
The apical root regions play an important role in analysis and diagnosis of many oral diseases. Automatic detection of such regions is consequently the first step toward computer-aided diagnosis of these diseases. In this paper we propose an automatic method for periapical root region detection by using the state-of-theart machine learning approaches. Specifically, we have adapted the AdaBoost classifier for apical root detection. One challenge in the task is the lack of training cases especially for diseased ones. To handle this problem, we boost the training set by including more root regions that are close to the annotated ones and decompose the original images to randomly generate negative samples. Based on these training samples, the Adaboost algorithm in combination with Haar wavelets is utilized in this task to train an apical root detector. The learned detector usually generates a large amount of true and false positives. In order to reduce the number of false positives, a confidence score for each candidate detection result is calculated for further purification. We first merge the detected regions by combining tightly overlapped detected candidate regions and then we use the confidence scores from the Adaboost detector to eliminate the false positives. The proposed method is evaluated on a dataset containing 39 annotated digitized oral X-Ray images from 21 patients. The experimental results show that our approach can achieve promising detection accuracy.
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Detection of insect damage in almonds
NASA Astrophysics Data System (ADS)
Kim, Soowon; Schatzki, Thomas F.
1999-01-01
Pinhole insect damage in natural almonds is very difficult to detect on-line. Further, evidence exists relating insect damage to aflatoxin contamination. Hence, for quality and health reasons, methods to detect and remove such damaged nuts are of great importance in this study, we explored the possibility of using x-ray imaging to detect pinhole damage in almonds by insects. X-ray film images of about 2000 almonds and x-ray linescan images of only 522 pinhole damaged almonds were obtained. The pinhole damaged region appeared slightly darker than non-damaged region in x-ray negative images. A machine recognition algorithm was developed to detect these darker regions. The algorithm used the first order and the second order information to identify the damaged region. To reduce the possibility of false positive results due to germ region in high resolution images, germ detection and removal routines were also included. With film images, the algorithm showed approximately an 81 percent correct recognition ratio with only 1 percent false positives whereas line scan images correctly recognized 65 percent of pinholes with about 9 percent false positives. The algorithms was very fast and efficient requiring only minimal computation time. If implemented on line, theoretical throughput of this recognition system would be 66 nuts/second.
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Widespread changes in network activity allow non-invasive detection of mesial temporal lobe seizures
Zepeda, Rodrigo; Cole, Andrew J.; Cash, Sydney S.
2016-01-01
Abstract Decades of experience with intracranial recordings in patients with epilepsy have demonstrated that seizures can occur in deep cortical regions such as the mesial temporal lobes without showing any obvious signs of seizure activity on scalp electroencephalogram. Predicated on the idea that these seizures are purely focal, currently, the only way to detect these ‘scalp-negative seizures’ is with intracranial recordings. However, intracranial recordings are only rarely performed in patients with epilepsy, and are almost never performed outside of the context of epilepsy. As such, little is known about scalp-negative seizures and their role in the natural history of epilepsy, their effect on cognitive function, and their association with other neurological diseases. Here, we developed a novel approach to non-invasively identify scalp-negative seizures arising from the mesial temporal lobe based on scalp electroencephalogram network connectivity measures. We identified 25 scalp-negative mesial temporal lobe seizures in 10 patients and obtained control records from an additional 13 patients, all of whom underwent recordings with foramen ovale electrodes and scalp electroencephalogram. Scalp data from these records were used to train a scalp-negative seizure detector, which consisted of a pair of logistic regression classifiers that used scalp electroencephalogram coherence properties as input features. On cross-validation performance, this detector correctly identified scalp-negative seizures in 40% of patients, and correctly identified the side of seizure onset for each seizure detected. In comparison, routine clinical interpretation of these scalp electroencephalograms failed to identify any of the scalp-negative seizures. Among the patients in whom the detector raised seizure alarms, 80% had scalp-negative mesial temporal lobe seizures. The detector had a false alarm rate of only 0.31 per day and a positive predictive value of 75%. Of the 13 control patients, false seizure alarms were raised in only one patient. The fact that our detector specifically recognizes focal mesial temporal lobe seizures based on scalp electroencephalogram coherence features, lends weight to the hypothesis that even focal seizures are a network phenomenon that involve widespread neural connectivity. Our scalp-negative seizure detector has clear clinical utility in patients with temporal lobe epilepsy, and its potential easily translates to other neurological disorders, such as Alzheimer’s disease, in which occult mesial temporal lobe seizures are suspected to play a significant role. Importantly, our work establishes a novel approach of using computational approaches to non-invasively detect deep seizure activity, without the need for invasive intracranial recordings. PMID:27474219
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El-Sayed, Abdulrahman M; Lauderdale, Diane S; Galea, Sandro
2010-12-01
Data about Arab-Americans, a growing ethnic minority, are not routinely collected in vital statistics, registry, or administrative data in the USA. The difficulty in identifying Arab-Americans using publicly available data sources is a barrier to health research about this group. Here, we validate an empirically based probabilistic Arab name algorithm (ANA) for identifying Arab-Americans in health research. We used data from all Michigan birth certificates between 2000 and 2005. Fathers' surnames and mothers' maiden names were coded as Arab or non-Arab according to the ANA. We calculated sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) of Arab ethnicity inferred using the ANA as compared to self-reported Arab ancestry. Statewide, the ANA had a specificity of 98.9%, a sensitivity of 50.3%, a PPV of 57.0%, and an NPV of 98.6%. Both the false-positive and false-negative rates were higher among men than among women. As the concentration of Arab-Americans in a study locality increased, the ANA false-positive rate increased and false-negative rate decreased. The ANA is highly specific but only moderately sensitive as a means of detecting Arab ancestry. Future research should compare health characteristics among Arab-American populations defined by Arab ancestry and those defined by the ANA.
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Yan, Liying; Huang, Lei; Xu, Liya; Huang, Jin; Ma, Fei; Zhu, Xiaohui; Tang, Yaqiong; Liu, Mingshan; Lian, Ying; Liu, Ping; Li, Rong; Lu, Sijia; Tang, Fuchou; Qiao, Jie; Xie, X Sunney
2015-12-29
In vitro fertilization (IVF), preimplantation genetic diagnosis (PGD), and preimplantation genetic screening (PGS) help patients to select embryos free of monogenic diseases and aneuploidy (chromosome abnormality). Next-generation sequencing (NGS) methods, while experiencing a rapid cost reduction, have improved the precision of PGD/PGS. However, the precision of PGD has been limited by the false-positive and false-negative single-nucleotide variations (SNVs), which are not acceptable in IVF and can be circumvented by linkage analyses, such as short tandem repeats or karyomapping. It is noteworthy that existing methods of detecting SNV/copy number variation (CNV) and linkage analysis often require separate procedures for the same embryo. Here we report an NGS-based PGD/PGS procedure that can simultaneously detect a single-gene disorder and aneuploidy and is capable of linkage analysis in a cost-effective way. This method, called "mutated allele revealed by sequencing with aneuploidy and linkage analyses" (MARSALA), involves multiple annealing and looping-based amplification cycles (MALBAC) for single-cell whole-genome amplification. Aneuploidy is determined by CNVs, whereas SNVs associated with the monogenic diseases are detected by PCR amplification of the MALBAC product. The false-positive and -negative SNVs are avoided by an NGS-based linkage analysis. Two healthy babies, free of the monogenic diseases of their parents, were born after such embryo selection. The monogenic diseases originated from a single base mutation on the autosome and the X-chromosome of the disease-carrying father and mother, respectively.
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Spore immobilization and its analytical performance for monitoring of aflatoxin M1 in milk.
Singh, V K; Singh, N A; Kumar, N; Raghu, H V; Sharma, Pradeep Kumar; Singh, K P; Yadav, Avinash
2014-12-01
Immobilization of Bacillus megaterium spores on Eppendorf tubes through physical adsorption has been used in the detection of aflatoxin M1 (AFM1) in milk within real time of 45 ± 5 min using visual observation of changes in a chromogenic substrate. The appearance of a sky-blue colour indicates the absence of AFM1 in milk, whereas no colour change indicates the presence of AFM1 in milk at a 0.5 ppb Codex maximum residue limit. The working performance of the immobilized spores was shown to persist for up to 6 months. Further, spores immobilized on 96-well black microtitre plates by physical adsorption and by entrapment on sensor disk showed a reduction in detection sensitivity to 0.25 ppb within a time period of 20 ± 5 min by measuring fluorescence using a microbiological plate reader through the addition of milk and fluorogenic substrate. A high fluorescence ratio indicated more substrate hydrolysis due to spore-germination-mediated release of marker enzymes of spores in the absence of AFM1 in milk; however, low fluorescence ratios indicated the presence of AFM1 at 0.25 ppb. Immobilized spores on 96-well microtitre plates and sensor disks have shown better reproducibility after storage at 4 °C for 6 months. Chromogenic assay showed 1.38% false-negative and 2.77% false-positive results while fluorogenic assay showed 4.16% false-positive and 2.77% false-negative results when analysed for AFM1 using 72 milk samples containing raw, pasteurized, and dried milk. Immobilization of spores makes these chromogenic and fluorogenic assays portable, selective, cost-effective for real-time detection of AFM1 in milk at the dairy farm, reception dock, and manufacturing units of the dairy industry.
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A PCR method based on 18S rRNA gene for detection of malaria parasite in Balochistan.
Shahwani, Zubeda; Aleem, Abdul; Ahmed, Nazeer; Mushtaq, Muhammad; Afridi, Sarwat
2016-12-01
To establish a polymerase chain reaction method based on 18S ribosomal ribonucleic acid gene for the detection of plasmodium deoxyribonucleic acid in patients suffering from malaria symptoms. This cross-sectional study was conducted from September 2013 to October 2014 in district Quetta of Pakistan's Balochistan province. Blood samples were collected from patients suffering from general symptoms of malaria. A polymerase chain reaction-based technique was applied for the diagnosis of malaria and detection of responsible species in the patients who were suspected to carry the parasite. Performance of this polymerase chain reaction method was compared against the microscopy results. Parasite number was also calculated for microscopy positive samples.All samples after the genomic deoxyribonucleic acid isolation were subjected to polymerase chain reaction amplification and agarose gel electrophoresis. Of the 200 samples, 114(57%) were confirmed as positive and 86(43%) as negative for malaria by microscopy. Polymerase chain reaction identified 124(62%) samples as positive and 76(38%) as negative for malaria. The comparative analysis of both diagnostic methods confirmed 109(54.5%) samples as positive by both techniques. Besides, 5(6.58%) samples were identified as false positive and 15(12.1%) samples as false negative by polymerase chain reaction. Sensitivity, specificity and positive predictive values for polymerase chain reaction in comparison to microscopy were 87.98%, 93.42% and 96%, respectively. Polymerase chain reaction-based methods in malaria diagnosis and species identification were found to be more effective than other techniques.
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CNV detection method optimized for high-resolution arrayCGH by normality test.
Ahn, Jaegyoon; Yoon, Youngmi; Park, Chihyun; Park, Sanghyun
2012-04-01
High-resolution arrayCGH platform makes it possible to detect small gains and losses which previously could not be measured. However, current CNV detection tools fitted to early low-resolution data are not applicable to larger high-resolution data. When CNV detection tools are applied to high-resolution data, they suffer from high false-positives, which increases validation cost. Existing CNV detection tools also require optimal parameter values. In most cases, obtaining these values is a difficult task. This study developed a CNV detection algorithm that is optimized for high-resolution arrayCGH data. This tool operates up to 1500 times faster than existing tools on a high-resolution arrayCGH of whole human chromosomes which has 42 million probes whose average length is 50 bases, while preserving false positive/negative rates. The algorithm also uses a normality test, thereby removing the need for optimal parameters. To our knowledge, this is the first formulation for CNV detecting problems that results in a near-linear empirical overall complexity for real high-resolution data. Copyright © 2012 Elsevier Ltd. All rights reserved.
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Online Conditional Outlier Detection in Nonstationary Time Series
Liu, Siqi; Wright, Adam; Hauskrecht, Milos
2017-01-01
The objective of this work is to develop methods for detecting outliers in time series data. Such methods can become the key component of various monitoring and alerting systems, where an outlier may be equal to some adverse condition that needs human attention. However, real-world time series are often affected by various sources of variability present in the environment that may influence the quality of detection; they may (1) explain some of the changes in the signal that would otherwise lead to false positive detections, as well as, (2) reduce the sensitivity of the detection algorithm leading to increase in false negatives. To alleviate these problems, we propose a new two-layer outlier detection approach that first tries to model and account for the nonstationarity and periodic variation in the time series, and then tries to use other observable variables in the environment to explain any additional signal variation. Our experiments on several data sets in different domains show that our method provides more accurate modeling of the time series, and that it is able to significantly improve outlier detection performance. PMID:29644345
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Online Conditional Outlier Detection in Nonstationary Time Series.
Liu, Siqi; Wright, Adam; Hauskrecht, Milos
2017-05-01
The objective of this work is to develop methods for detecting outliers in time series data. Such methods can become the key component of various monitoring and alerting systems, where an outlier may be equal to some adverse condition that needs human attention. However, real-world time series are often affected by various sources of variability present in the environment that may influence the quality of detection; they may (1) explain some of the changes in the signal that would otherwise lead to false positive detections, as well as, (2) reduce the sensitivity of the detection algorithm leading to increase in false negatives. To alleviate these problems, we propose a new two-layer outlier detection approach that first tries to model and account for the nonstationarity and periodic variation in the time series, and then tries to use other observable variables in the environment to explain any additional signal variation. Our experiments on several data sets in different domains show that our method provides more accurate modeling of the time series, and that it is able to significantly improve outlier detection performance.
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Concordance of polymerase chain reaction with human immunodeficiency virus antibody detection.
Horsburgh, C R; Ou, C Y; Jason, J; Holmberg, S D; Lifson, A R; Moore, J L; Ward, J W; Seage, G R; Mayer, K H; Evatt, B L
1990-08-01
To evaluate the correlation of detection of human immunodeficiency virus (HIV) by polymerase chain reaction (PCR) with detection of HIV antibody, 271 simultaneous serum and peripheral blood mononuclear cell samples were examined from 242 persons whose activities placed them at increased risk for HIV infection: 142 from homosexual men, 86 from hemophilic men, and 43 from heterosexual partners of HIV-infected persons. PCR was performed using the gag region primer pair SK38/39 and the env region primer pairs SK68/69 and CO71/72. Amplified HIV DNA was detected using specific oligomer probes. Of 63 HIV antibody-positive samples, 58 (92%) had HIV DNA by PCR. Of 208 HIV antibody-negative samples, 7 (3.4%) had HIV DNA by PCR. On follow-up, 4 of the latter persons were seropositive when next tested; 2 were well and antibody- and PCR-negative; 1 had died of a stroke before retesting. Thus, PCR detects HIV in most antibody-positive persons; detection is increased by use of multiple primer pairs. PCR-positive antibody-negative specimens may indicate HIV infection in which antibody has not yet developed or may be false-positive PCR results. When PCR is discordant with HIV antibody, testing of additional specimens and clinical follow-up are necessary to assess HIV infection status.
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Simmons, Ann Marie; Rowneki, Mazhgan; Parmar, Heta; Cao, Yuan; Ryan, Jamie; Banada, Padmapriya P.; Deshpande, Srinidhi; Shenai, Shubhada; Gall, Alexander; Glass, Jennifer; Krieswirth, Barry; Schumacher, Samuel G.; Nabeta, Pamela; Tukvadze, Nestani; Rodrigues, Camilla; Skrahina, Alena; Tagliani, Elisa; Cirillo, Daniela M.; Davidow, Amy; Denkinger, Claudia M.; Persing, David; Kwiatkowski, Robert; Jones, Martin
2017-01-01
ABSTRACT The Xpert MTB/RIF assay (Xpert) is a rapid test for tuberculosis (TB) and rifampin resistance (RIF-R) suitable for point-of-care testing. However, it has decreased sensitivity in smear-negative sputum, and false identification of RIF-R occasionally occurs. We developed the Xpert MTB/RIF Ultra assay (Ultra) to improve performance. Ultra and Xpert limits of detection (LOD), dynamic ranges, and RIF-R rpoB mutation detection were tested on Mycobacterium tuberculosis DNA or sputum samples spiked with known numbers of M. tuberculosis H37Rv or Mycobacterium bovis BCG CFU. Frozen and prospectively collected clinical samples from patients suspected of having TB, with and without culture-confirmed TB, were also tested. For M. tuberculosis H37Rv, the LOD was 15.6 CFU/ml of sputum for Ultra versus 112.6 CFU/ml of sputum for Xpert, and for M. bovis BCG, it was 143.4 CFU/ml of sputum for Ultra versus 344 CFU/ml of sputum for Xpert. Ultra resulted in no false-positive RIF-R specimens, while Xpert resulted in two false-positive RIF-R specimens. All RIF-R-associated M. tuberculosis rpoB mutations tested were identified by Ultra. Testing on clinical sputum samples, Ultra versus Xpert, resulted in an overall sensitivity of 87.5% (95% confidence interval [CI], 82.1, 91.7) versus 81.0% (95% CI, 74.9, 86.2) and a sensitivity on sputum smear-negative samples of 78.9% (95% CI, 70.0, 86.1) versus 66.1% (95% CI, 56.4, 74.9). Both tests had a specificity of 98.7% (95% CI, 93.0, 100), and both had comparable accuracies for detection of RIF-R in these samples. Ultra should significantly improve TB detection, especially in patients with paucibacillary disease, and may provide more-reliable RIF-R detection. PMID:28851844
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Tafra, Lorraine; Lannin, Donald R.; Swanson, Melvin S.; Van Eyk, Jason J.; Verbanac, Kathryn M.; Chua, Arlene N.; Ng, Peter C.; Edwards, Maxine S.; Halliday, Bradford E.; Henry, C. Alan; Sommers, Linda M.; Carman, Claire M.; Molin, Melinda R.; Yurko, John E.; Perry, Roger R.; Williams, Robert
2001-01-01
Objective To determine the factors associated with false-negative results on sentinel node biopsy and sentinel node localization (identification rate) in patients with breast cancer enrolled in a multicenter trial using a combination technique of isosulfan blue with technetium sulfur colloid (Tc99). Summary Background Data Sentinel node biopsy is a diagnostic test used to detect breast cancer metastases. To test the reliability of this method, a complete lymph node dissection must be performed to determine the false-negative rate. Single-institution series have reported excellent results, although one multicenter trial reported a false-negative rate as high as 29% using radioisotope alone. A multicenter trial was initiated to test combined use of Tc99 and isosulfan blue. Methods Investigators (both private-practice and academic surgeons) were recruited after attending a course on the technique of sentinel node biopsy. No investigator participated in a learning trial before entering patients. Tc99 and isosulfan blue were injected into the peritumoral region. Results Five hundred twenty-nine patients underwent 535 sentinel node biopsy procedures for an overall identification rate in finding a sentinel node of 87% and a false-negative rate of 13%. The identification rate increased and the false-negative rate decreased to 90% and 4.3%, respectively, after investigators had performed more than 30 cases. Univariate analysis of tumor showed the poorest success rate with older patients and inexperienced surgeons. Multivariate analysis identified both age and experience as independent predictors of failure. However, with older patients, inexperienced surgeons, and patients with five or more metastatic axillary nodes, the false-negative rate was consistently greater. Conclusions This multicenter trial, from both private practice and academic institutions, is an excellent indicator of the general utility of sentinel node biopsy. It establishes the factors that play an important role (patient age, surgical experience, tumor location) and those that are irrelevant (prior surgery, tumor size, Tc99 timing). This widens the applicability of the technique and identifies factors that require further investigation. PMID:11141225
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Discrimination of plant-parasitic nematodes from complex soil communities using ecometagenetics.
Porazinska, Dorota L; Morgan, Matthew J; Gaspar, John M; Court, Leon N; Hardy, Christopher M; Hodda, Mike
2014-07-01
Many plant pathogens are microscopic, cryptic, and difficult to diagnose. The new approach of ecometagenetics, involving ultrasequencing, bioinformatics, and biostatistics, has the potential to improve diagnoses of plant pathogens such as nematodes from the complex mixtures found in many agricultural and biosecurity situations. We tested this approach on a gradient of complexity ranging from a few individuals from a few species of known nematode pathogens in a relatively defined substrate to a complex and poorly known suite of nematode pathogens in a complex forest soil, including its associated biota of unknown protists, fungi, and other microscopic eukaryotes. We added three known but contrasting species (Pratylenchus neglectus, the closely related P. thornei, and Heterodera avenae) to half the set of substrates, leaving the other half without them. We then tested whether all nematode pathogens-known and unknown, indigenous, and experimentally added-were detected consistently present or absent. We always detected the Pratylenchus spp. correctly and with the number of sequence reads proportional to the numbers added. However, a single cyst of H. avenae was only identified approximately half the time it was present. Other plant-parasitic nematodes and nematodes from other trophic groups were detected well but other eukaryotes were detected less consistently. DNA sampling errors or informatic errors or both were involved in misidentification of H. avenae; however, the proportions of each varied in the different bioinformatic pipelines and with different parameters used. To a large extent, false-positive and false-negative errors were complementary: pipelines and parameters with the highest false-positive rates had the lowest false-negative rates and vice versa. Sources of error identified included assumptions in the bioinformatic pipelines, slight differences in primer regions, the number of sequence reads regarded as the minimum threshold for inclusion in analysis, and inaccessible DNA in resistant life stages. Identification of the sources of error allows us to suggest ways to improve identification using ecometagenetics.
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The effect of algorithms on copy number variant detection.
Tsuang, Debby W; Millard, Steven P; Ely, Benjamin; Chi, Peter; Wang, Kenneth; Raskind, Wendy H; Kim, Sulgi; Brkanac, Zoran; Yu, Chang-En
2010-12-30
The detection of copy number variants (CNVs) and the results of CNV-disease association studies rely on how CNVs are defined, and because array-based technologies can only infer CNVs, CNV-calling algorithms can produce vastly different findings. Several authors have noted the large-scale variability between CNV-detection methods, as well as the substantial false positive and false negative rates associated with those methods. In this study, we use variations of four common algorithms for CNV detection (PennCNV, QuantiSNP, HMMSeg, and cnvPartition) and two definitions of overlap (any overlap and an overlap of at least 40% of the smaller CNV) to illustrate the effects of varying algorithms and definitions of overlap on CNV discovery. We used a 56 K Illumina genotyping array enriched for CNV regions to generate hybridization intensities and allele frequencies for 48 Caucasian schizophrenia cases and 48 age-, ethnicity-, and gender-matched control subjects. No algorithm found a difference in CNV burden between the two groups. However, the total number of CNVs called ranged from 102 to 3,765 across algorithms. The mean CNV size ranged from 46 kb to 787 kb, and the average number of CNVs per subject ranged from 1 to 39. The number of novel CNVs not previously reported in normal subjects ranged from 0 to 212. Motivated by the availability of multiple publicly available genome-wide SNP arrays, investigators are conducting numerous analyses to identify putative additional CNVs in complex genetic disorders. However, the number of CNVs identified in array-based studies, and whether these CNVs are novel or valid, will depend on the algorithm(s) used. Thus, given the variety of methods used, there will be many false positives and false negatives. Both guidelines for the identification of CNVs inferred from high-density arrays and the establishment of a gold standard for validation of CNVs are needed.
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Controlling false-negative errors in microarray differential expression analysis: a PRIM approach.
Cole, Steve W; Galic, Zoran; Zack, Jerome A
2003-09-22
Theoretical considerations suggest that current microarray screening algorithms may fail to detect many true differences in gene expression (Type II analytic errors). We assessed 'false negative' error rates in differential expression analyses by conventional linear statistical models (e.g. t-test), microarray-adapted variants (e.g. SAM, Cyber-T), and a novel strategy based on hold-out cross-validation. The latter approach employs the machine-learning algorithm Patient Rule Induction Method (PRIM) to infer minimum thresholds for reliable change in gene expression from Boolean conjunctions of fold-induction and raw fluorescence measurements. Monte Carlo analyses based on four empirical data sets show that conventional statistical models and their microarray-adapted variants overlook more than 50% of genes showing significant up-regulation. Conjoint PRIM prediction rules recover approximately twice as many differentially expressed transcripts while maintaining strong control over false-positive (Type I) errors. As a result, experimental replication rates increase and total analytic error rates decline. RT-PCR studies confirm that gene inductions detected by PRIM but overlooked by other methods represent true changes in mRNA levels. PRIM-based conjoint inference rules thus represent an improved strategy for high-sensitivity screening of DNA microarrays. Freestanding JAVA application at http://microarray.crump.ucla.edu/focus
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False Positives in Exoplanet Detection
NASA Astrophysics Data System (ADS)
Leuquire, Jacob; Kasper, David; Jang-Condell, Hannah; Kar, Aman; Sorber, Rebecca; Suhaimi, Afiq; KELT (Kilodegree Extremely Little Telescope)
2018-06-01
Our team at the University of Wyoming uses a 0.6 m telescope at RBO (Red Buttes Observatory) to help confirm results on potential exoplanet candidates from low resolution, wide field surveys shared by the KELT (Kilodegree Extremely Little Telescope) team. False positives are common in this work. We carry out transit photometry, and this method comes with special types of false positives. The most common false positive seen at the confirmation level is an EB (eclipsing binary). Low resolution images are great in detecting multiple sources for photometric dips in light curves, but they lack the precision to decipher single targets at an accurate level. For example, target star KC18C030621 needed RBO’s photometric precision to determine there was a nearby EB causing exoplanet type light curves. Identifying false positives with our telescope is important work because it helps eliminate the waste of time taken by more expensive telescopes trying to rule out negative candidate stars. It also furthers the identification of other types of photometric events, like eclipsing binaries, so they can be studied on their own.
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Deep venous thrombophlebitis: detection with 4-hour versus 24-hour platelet scintigraphy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Seabold, J.E.; Conrad, G.R.; Ponto, J.A.
Thirty-one nonheparinized patients with suspected deep venous thrombophlebitis (DVT) underwent contrast venography and indium-111 platelet scintigraphy (In-111 PS). Venography permitted identification of acute DVT in 12 of 31 cases (39%). One additional patient was considered to have acute DVT despite nonconclusive venography results. In-111 PS results were positive at 4 hours in nine of 13 cases (69%) and at 24 hours in 12 of 13 cases (92%). Two of four patients with false-negative 4-hour In-111 PS studies had received warfarin. Thus, the sensitivity of 4-hour In-111 PS in patients not receiving anticoagulants was 82%. Venography results were negative for acutemore » DVT in 18 cases, and 4-hour In-111 PS studies were negative or equivocal in each. In-111 PS is an alternative to contrast venography for detecting acute DVT. If 4-hour In-111 PS results are positive, anticoagulation can be initiated. Delayed images are necessary if the 4-hour images are negative or equivocal.« less
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2014-01-01
Introduction Interval cancers are tumors arising after a negative screening episode and before the next screening invitation. They can be classified into true interval cancers, false-negatives, minimal-sign cancers, and occult tumors based on mammographic findings in screening and diagnostic mammograms. This study aimed to describe tumor-related characteristics and the association of breast density and tumor phenotype within four interval cancer categories. Methods We included 2,245 invasive tumors (1,297 screening-detected and 948 interval cancers) diagnosed from 2000 to 2009 among 645,764 women aged 45 to 69 who underwent biennial screening in Spain. Interval cancers were classified by a semi-informed retrospective review into true interval cancers (n = 455), false-negatives (n = 224), minimal-sign (n = 166), and occult tumors (n = 103). Breast density was evaluated using Boyd’s scale and was conflated into: <25%; 25 to 50%; 50 to 75%; >75%. Tumor-related information was obtained from cancer registries and clinical records. Tumor phenotype was defined as follows: luminal A: ER+/HER2- or PR+/HER2-; luminal B: ER+/HER2+ or PR+/HER2+; HER2: ER-/PR-/HER2+; triple-negative: ER-/PR-/HER2-. The association of tumor phenotype and breast density was assessed using a multinomial logistic regression model. Adjusted odds ratios (OR) and 95% confidence intervals (95% CI) were calculated. All statistical tests were two-sided. Results Forty-eight percent of interval cancers were true interval cancers and 23.6% false-negatives. True interval cancers were associated with HER2 and triple-negative phenotypes (OR = 1.91 (95% CI:1.22-2.96), OR = 2.07 (95% CI:1.42-3.01), respectively) and extremely dense breasts (>75%) (OR = 1.67 (95% CI:1.08-2.56)). However, among true interval cancers a higher proportion of triple-negative tumors was observed in predominantly fatty breasts (<25%) than in denser breasts (28.7%, 21.4%, 11.3% and 14.3%, respectively; <0.001). False-negatives and occult tumors had similar phenotypic characteristics to screening-detected cancers, extreme breast density being strongly associated with occult tumors (OR = 6.23 (95% CI:2.65-14.66)). Minimal-sign cancers were biologically close to true interval cancers but showed no association with breast density. Conclusions Our findings revealed that both the distribution of tumor phenotype and breast density play specific and independent roles in each category of interval cancer. Further research is needed to understand the biological basis of the overrepresentation of triple-negative phenotype among predominantly fatty breasts in true interval cancers. PMID:24410848
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Reddy, T; McLaughlin, P D; Mallinson, P I; Reagan, A C; Munk, P L; Nicolaou, S; Ouellette, H A
2015-02-01
The purpose of this study is to describe our initial clinical experience with dual-energy computed tomography (DECT) virtual non-calcium (VNC) images for the detection of bone marrow (BM) edema in patients with suspected hip fracture following trauma. Twenty-five patients presented to the emergency department at a level 1 trauma center between January 1, 2011 and January 1, 2013 with clinical suspicion of hip fracture and normal radiographs were included. All CT scans were performed on a dual-source, dual-energy CT system. VNC images were generated using prototype software and were compared to regular bone reconstructions by two musculoskeletal radiologists in consensus. Radiological and/or clinical diagnosis of fracture at 30-day follow-up was used as the reference standard. Twenty-one patients were found to have DECT-VNC signs of bone marrow edema. Eighteen of these 21 patients were true positive and three were false positive. A concordant fracture was clearly seen on bone reconstruction images in 15 of the 18 true positive cases. In three cases, DECT-VNC was positive for bone marrow edema where bone reconstruction CT images were negative. Four patients demonstrated no DECT-VNC signs of bone marrow edema: two cases were true negative, two cases were false negative. When compared with the gold standard of hip fracture determined at retrospective follow-up, the sensitivity of DECT-VNC images of the hip was 90 %, specificity was 40 %, positive predictive value was 86 %, and negative predictive value was 50 %. Our initial experience would suggest that DECT-VNC is highly sensitive but poorly specific in the diagnosis of hip fractures in patients with normal radiographs. The value of DECT-VNC primarily lies in its ability to help detect fractures which may be subtle or undetectable on bone reconstruction CT images.
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Zhang, Guodong; Brown, Eric W.; González-Escalona, Narjol
2011-01-01
Contamination of foods, especially produce, with Salmonella spp. is a major concern for public health. Several methods are available for the detection of Salmonella in produce, but their relative efficiency for detecting Salmonella in commonly consumed vegetables, often associated with outbreaks of food poisoning, needs to be confirmed. In this study, the effectiveness of three molecular methods for detection of Salmonella in six produce matrices was evaluated and compared to the FDA microbiological detection method. Samples of cilantro (coriander leaves), lettuce, parsley, spinach, tomato, and jalapeno pepper were inoculated with Salmonella serovars at two different levels (105 and <101 CFU/25 g of produce). The inoculated produce was assayed by the FDA Salmonella culture method (Bacteriological Analytical Manual) and by three molecular methods: quantitative real-time PCR (qPCR), quantitative reverse transcriptase real-time PCR (RT-qPCR), and loop-mediated isothermal amplification (LAMP). Comparable results were obtained by these four methods, which all detected as little as 2 CFU of Salmonella cells/25 g of produce. All control samples (not inoculated) were negative by the four methods. RT-qPCR detects only live Salmonella cells, obviating the danger of false-positive results from nonviable cells. False negatives (inhibition of either qPCR or RT-qPCR) were avoided by the use of either a DNA or an RNA amplification internal control (IAC). Compared to the conventional culture method, the qPCR, RT-qPCR, and LAMP assays allowed faster and equally accurate detection of Salmonella spp. in six high-risk produce commodities. PMID:21803916
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An evaluation of the Monosticon rapid slide test diagnosis of infectious mononucleosis
Scott, G. L.; Priest, C. J.
1972-01-01
A new rapid slide test for the detection of infectious mononucleosis heterophile antibody has been compared with the Paul-Bunnell absorption test. Out of 200 sera, 46 were seropositive for infectious mononucleosis by the Paul-Bunnell test and 43 of these were detected by the Monosticon test; the three Monosticon-negative sera were of low titre. There was no problem with false positive reactions due to heterophile antibody not specific for infectious mononucleosis. PMID:4678188
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Helmi, K; Jacob, P; Charni-Ben-Tabassi, N; Delabre, K; Arnal, C
2011-09-01
To select a reliable method for bacteriophage concentration prior detection by culture from surface water, groundwater and drinking water to enhance the sensitivity of the standard methods ISO 10705-1 & 2. Artificially contaminated (groundwater and drinking water) and naturally contaminated (surface water) 1-litre samples were processed for bacteriophages detection. The spiked samples were inoculated with about 150 PFU of F-specific RNA bacteriophages and somatic coliphages using wastewater. Bacteriophage detection in the water samples was achieved using the standard method without and with a concentration step (electropositive Anodisc membrane or a pretreated electronegative Micro Filtration membrane, MF). For artificially contaminated matrices (drinking and ground waters), recovery rates using the concentration step were superior to 70% whilst analyses without concentration step mainly led to false negative results. Besides, the MF membrane presented higher performances compared with the Anodisc membrane. The concentration of a large volume of water (up to one litre) on a filter membrane avoids false negative results obtained by direct analysis as it allows detecting low number of bacteriophages in water samples. The addition of concentration step before applying the standard method could be useful to enhance the reliability of bacteriophages monitoring in water samples as bio-indicators to highlight faecal pollution. © No claim to French Government works. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.
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Sakurai, Fuminori; Narii, Nobuhiro; Tomita, Kyoko; Togo, Shinsaku; Takahashi, Kazuhisa; Machitani, Mitsuhiro; Tachibana, Masashi; Ouchi, Masaaki; Katagiri, Nobuyoshi; Urata, Yasuo; Fujiwara, Toshiyoshi; Mizuguchi, Hiroyuki
2016-01-01
Circulating tumor cells (CTCs) are promising biomarkers in several cancers, and thus methods and apparatuses for their detection and quantification in the blood have been actively pursued. A novel CTC detection system using a green fluorescence protein (GFP)–expressing conditionally replicating adenovirus (Ad) (rAd-GFP) was recently developed; however, there is concern about the production of false-positive cells (GFP-positive normal blood cells) when using rAd-GFP, particularly at high titers. In addition, CTCs lacking or expressing low levels of coxsackievirus–adenovirus receptor (CAR) cannot be detected by rAd-GFP, because rAd-GFP is constructed based on Ad serotype 5, which recognizes CAR. In order to suppress the production of false-positive cells, sequences perfectly complementary to blood cell–specific microRNA, miR-142-3p, were incorporated into the 3′-untranslated region of the E1B and GFP genes. In addition, the fiber protein was replaced with that of Ad serotype 35, which recognizes human CD46, creating rAdF35-142T-GFP. rAdF35-142T-GFP efficiently labeled not only CAR-positive tumor cells but also CAR-negative tumor cells with GFP. The numbers of false-positive cells were dramatically lower for rAdF35-142T-GFP than for rAd-GFP. CTCs in the blood of cancer patients were detected by rAdF35-142T-GFP with a large reduction in false-positive cells. PMID:26966699
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Yeo, Zhen Xuan; Wong, Joshua Chee Leong; Rozen, Steven G; Lee, Ann Siew Gek
2014-06-24
The Ion Torrent PGM is a popular benchtop sequencer that shows promise in replacing conventional Sanger sequencing as the gold standard for mutation detection. Despite the PGM's reported high accuracy in calling single nucleotide variations, it tends to generate many false positive calls in detecting insertions and deletions (indels), which may hinder its utility for clinical genetic testing. Recently, the proprietary analytical workflow for the Ion Torrent sequencer, Torrent Suite (TS), underwent a series of upgrades. We evaluated three major upgrades of TS by calling indels in the BRCA1 and BRCA2 genes. Our analysis revealed that false negative indels could be generated by TS under both default calling parameters and parameters adjusted for maximum sensitivity. However, indel calling with the same data using the open source variant callers, GATK and SAMtools showed that false negatives could be minimised with the use of appropriate bioinformatics analysis. Furthermore, we identified two variant calling measures, Quality-by-Depth (QD) and VARiation of the Width of gaps and inserts (VARW), which substantially reduced false positive indels, including non-homopolymer associated errors without compromising sensitivity. In our best case scenario that involved the TMAP aligner and SAMtools, we achieved 100% sensitivity, 99.99% specificity and 29% False Discovery Rate (FDR) in indel calling from all 23 samples, which is a good performance for mutation screening using PGM. New versions of TS, BWA and GATK have shown improvements in indel calling sensitivity and specificity over their older counterpart. However, the variant caller of TS exhibits a lower sensitivity than GATK and SAMtools. Our findings demonstrate that although indel calling from PGM sequences may appear to be noisy at first glance, proper computational indel calling analysis is able to maximize both the sensitivity and specificity at the single base level, paving the way for the usage of this technology for future clinical genetic testing.
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Cliquet, F; McElhinney, L M; Servat, A; Boucher, J M; Lowings, J P; Goddard, T; Mansfield, K L; Fooks, A R
2004-04-01
A protocol suitable for the detection of rabies virus-specific antibodies in serum samples from companion animals using an enzyme linked immunosorbent assay (ELISA) is described. This method has been used successfully for the qualitative assessment of rabies virus-specific antibodies in serum samples from a cohort of vaccinated dogs and cats. In two initial field studies, a variable population of field samples from the Veterinary Laboratories Agency (VLA), United Kingdom were tested. In the first study (n = 1000), the number of false-positive and false-negative results was 11 samples (1.1%) and 67 samples (6.7%), respectively. In the second study (n = 920), the number of false-positive and false-negative results was 7 samples (0.8%) and 52 samples (5.7%). In a third study, undertaken at l'Agence Française de Sécurité Sanitaire des Aliments (AFSSA), Nancy, France (n = 440), 1 false-positive sample (0.23%) and 91 (20.7%) false-negative samples were identified. Data generated using this prototype ELISA indicate a strong correlation for specificity when compared to the gold standard fluorescent antibody virus neutralisation (FAVN) test. Although the ELISA has a lower sensitivity than the FAVN test, it is a useful tool for rapidly screening serum samples from vaccinated companion animals. Using a cut-off value of 0.6 EU/ml, the sensitivity (R = % from VLA and 79% from AFSSA) and specificity (R = 97.3%) indices between the ELISA compared favourably with data generated using the FAVN test. The major advantages of the ELISA test are that it is a qualitative tool that can be completed in four hours, does not require the use of live virus and can be performed without the need for specialised laboratory containment. This contrasts with 4 days using conventional rabies antibody virus neutralisation assays. Using the current format, the ELISA assay described would be a valuable screening tool for the detection of rabies antibodies from vaccinated domestic animals in combination with other Office International des Epizooties (OIE) accepted serological tests.
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Amrhein, Timothy J; Mostertz, William; Matheus, Maria Gisele; Maass-Bolles, Genevieve; Sharma, Komal; Collins, Heather R; Kranz, Peter G
2017-02-01
Subdural hematomas (SDHs) comprise a significant percentage of missed intracranial hemorrhage on axial brain CT. SDH detection rates could be improved with the addition of reformatted images. Though performed at some centers, the potential additional diagnostic sensitivity of reformatted images has not yet been investigated. The purpose of our study is to determine if the addition of coronal and sagittal reformatted images to an axial brain CT increases the sensitivity and specificity for detection of acute traumatic SDH. We retrospectively reviewed consecutive brain CTs acquired for acute trauma that contained new SDHs. An equivalent number of normal brain CTs served as control. Paired sets of images were created for each case: (1) axial images only ("axial only") and (2) axial, coronal, sagittal images ("reformat added"). Three readers interpreted both the axial only and companion reformat added for each case, separated by 1 month. Reading times and SDH detection rates were compared. One hundred SDH and 100 negative examinations were collected. Sensitivity and specificity for the axial-only scans were 75.7 and 94.3 %, respectively, compared with 88.3 and 98.3 % for reformat added. There was a 24.3 % false negative (missed SDH) rate with axial-only scans versus 11.7 % with reformat added (p = <0.001). Median reader interpretation times were longer with the addition of reformatted images (125 versus 89 s), but this difference was not significant (p = 0.23). The addition of coronal and sagittal images in trauma brain CT resulted in improved sensitivity and specificity as well as a reduction in SDH false negatives by greater than 50 %. Reformatted images substantially reduce the number of missed SDHs compared with axial images alone.
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Porter, Stephen; Taylor, Kristian; Ten Brinke, Leanne
2008-01-01
Despite a large body of false memory research, little has addressed the potential influence of an event's emotional content on susceptibility to false recollections. The Paradoxical Negative Emotion (PNE) hypothesis predicts that negative emotion generally facilitates memory but also heightens susceptibility to false memories. Participants were asked whether they could recall 20 "widely publicised" public events (half fictitious) ranging in emotional valence, with or without visual cues. Participants recalled a greater number of true negative events (M=3.31/5) than true positive (M=2.61/5) events. Nearly everyone (95%) came to recall at least one false event (M=2.15 false events recalled). Further, more than twice as many participants recalled any false negative (90%) compared to false positive (41.7%) events. Negative events, in general, were associated with more detailed memories and false negative event memories were more detailed than false positive event memories. Higher dissociation scores were associated with false recollections of negative events, specifically.
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Neural network for photoplethysmographic respiratory rate monitoring
NASA Astrophysics Data System (ADS)
Johansson, Anders
2001-10-01
The photoplethysmographic signal (PPG) includes respiratory components seen as frequency modulation of the heart rate (respiratory sinus arrhythmia, RSA), amplitude modulation of the cardiac pulse, and respiratory induced intensity variations (RIIV) in the PPG baseline. The aim of this study was to evaluate the accuracy of these components in determining respiratory rate, and to combine the components in a neural network for improved accuracy. The primary goal is to design a PPG ventilation monitoring system. PPG signals were recorded from 15 healthy subjects. From these signals, the systolic waveform, diastolic waveform, respiratory sinus arrhythmia, pulse amplitude and RIIV were extracted. By using simple algorithms, the rates of false positive and false negative detection of breaths were calculated for each of the five components in a separate analysis. Furthermore, a simple neural network (NN) was tried out in a combined pattern recognition approach. In the separate analysis, the error rates (sum of false positives and false negatives) ranged from 9.7% (pulse amplitude) to 14.5% (systolic waveform). The corresponding value of the NN analysis was 9.5-9.6%.
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Validating Actigraphy as a Measure of Sleep for Preschool Children
Bélanger, Marie-Ève; Bernier, Annie; Paquet, Jean; Simard, Valérie; Carrier, Julie
2013-01-01
Study Objectives: The algorithms used to derive sleep variables from actigraphy were developed with adults. Because children change position during sleep more often than adults, algorithms may detect wakefulness when the child is actually sleeping (false negative). This study compares the validity of three algorithms for detecting sleep with actigraphy by comparing them to PSG in preschoolers. The putative influence of device location (wrist or ankle) is also examined. Methods: Twelve children aged 2 to 5 years simultaneously wore an actigraph on an ankle and a wrist (Actiwatch-L, Mini-Mitter/Respironics) during a night of PSG recording at home. Three algorithms were tested: one recommended for adults and two designed to decrease false negative detection of sleep in children. Results: Actigraphy generally showed good sensitivity (> 95%; PSG sleep detection) but low specificity (± 50%; PSG wake detection). Intraclass correlations between PSG and actigraphy variables were strong (> 0.80) for sleep latency, sleep duration, and sleep efficiency, but weak for number of awakenings (< 0.40). The two algorithms designed for children enhanced the validity of actigraphy in preschoolers and increased the proportion of actigraphy-scored wake epochs scored that were also PSG-identified as wake. Sleep variables derived from the ankle and wrist were not statistically different. Conclusion: Despite the weak detection of wakefulness, Acti-watch-L appears to be a useful instrument for assessing sleep in preschoolers when used with an adapted algorithm. Citation: Bélanger M; Bernier A; Paquet J; Simard V; Julie Carrier J. Validating actigraphy as a measure of sleep for pre-school children. J Clin Sleep Med 2013;9(7):701-706. PMID:23853565
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Pimkina, Edita; Zablockis, Rolandas; Nikolayevskyy, Vladyslav; Danila, Edvardas; Davidaviciene, Edita
2015-11-01
Drug-resistant tuberculosis (TB) is an important public health problem in Lithuania with MDR rates in new cases reaching 11% in 2012. Currently available diagnostic tools are not fully adequate for an accurate and rapid result for diagnosis of TB and MDR-TB. To evaluate the performance of Xpert(®) MTB/RIF assay for an early diagnosis of TB and detection of rifampicin (RIF) resistance in routine settings in Lithuania. A total of 833 individual respiratory samples obtained from patients previously treated for TB and MDR-TB contacts were tested using the Xpert MTB/RIF assay. Performance characteristics of the assay for TB and RIF resistance detection were calculated using culture and phenotypical DST results as a gold standard. The overall sensitivity and specificity of the Xpert MTB/RIF assay for TB detection were 93.7% and 91.7%, respectively with the sensitivity for smear-negative specimens reaching 82.5%. Resistance to RIF was detected in 81 (20.7%) primary specimens with no false negative results; there were 4/225 (1.8%) false-positives among strains sensitive to rifampicin. Overall sensitivity and specificity of the molecular assay for detection of RIF resistance calculated against phenotypic DST results were 100% and 98.2%, respectively. Our results demonstrate very good performance of the Xpert MTB/RIF assay for the detection of TB and RIF resistance on primary respiratory specimens. It provides strong evidence that implementation of the assay for routine laboratory diagnosis in high drug-resistance settings may improve and facilitate TB diagnosis. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Evaluation of 5 different labeled polymer immunohistochemical detection systems.
Skaland, Ivar; Nordhus, Marit; Gudlaugsson, Einar; Klos, Jan; Kjellevold, Kjell H; Janssen, Emiel A M; Baak, Jan P A
2010-01-01
Immunohistochemical staining is important for diagnosis and therapeutic decision making but the results may vary when different detection systems are used. To analyze this, 5 different labeled polymer immunohistochemical detection systems, REAL EnVision, EnVision Flex, EnVision Flex+ (Dako, Glostrup, Denmark), NovoLink (Novocastra Laboratories Ltd, Newcastle Upon Tyne, UK) and UltraVision ONE (Thermo Fisher Scientific, Fremont, CA) were tested using 12 different, widely used mouse and rabbit primary antibodies, detecting nuclear, cytoplasmic, and membrane antigens. Serial sections of multitissue blocks containing 4% formaldehyde fixed paraffin embedded material were selected for their weak, moderate, and strong staining for each antibody. Specificity and sensitivity were evaluated by subjective scoring and digital image analysis. At optimal primary antibody dilution, digital image analysis showed that EnVision Flex+ was the most sensitive system (P < 0.005), with means of 8.3, 13.4, 20.2, and 41.8 gray scale values stronger staining than REAL EnVision, EnVision Flex, NovoLink, and UltraVision ONE, respectively. NovoLink was the second most sensitive system for mouse antibodies, but showed low sensitivity for rabbit antibodies. Due to low sensitivity, 2 cases with UltraVision ONE and 1 case with NovoLink stained false negatively. None of the detection systems showed any distinct false positivity, but UltraVision ONE and NovoLink consistently showed weak background staining both in negative controls and at optimal primary antibody dilution. We conclude that there are significant differences in sensitivity, specificity, costs, and total assay time in the immunohistochemical detection systems currently in use.
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DEEPEN: A negation detection system for clinical text incorporating dependency relation into NegEx
Mehrabi, Saeed; Krishnan, Anand; Sohn, Sunghwan; Roch, Alexandra M; Schmidt, Heidi; Kesterson, Joe; Beesley, Chris; Dexter, Paul; Schmidt, C. Max; Liu, Hongfang; Palakal, Mathew
2018-01-01
In Electronic Health Records (EHRs), much of valuable information regarding patients’ conditions is embedded in free text format. Natural language processing (NLP) techniques have been developed to extract clinical information from free text. One challenge faced in clinical NLP is that the meaning of clinical entities is heavily affected by modifiers such as negation. A negation detection algorithm, NegEx, applies a simplistic approach that has been shown to be powerful in clinical NLP. However, due to the failure to consider the contextual relationship between words within a sentence, NegEx fails to correctly capture the negation status of concepts in complex sentences. Incorrect negation assignment could cause inaccurate diagnosis of patients’ condition or contaminated study cohorts. We developed a negation algorithm called DEEPEN to decrease NegEx’s false positives by taking into account the dependency relationship between negation words and concepts within a sentence using Stanford dependency parser. The system was developed and tested using EHR data from Indiana University (IU) and it was further evaluated on Mayo Clinic dataset to assess its generalizability. The evaluation results demonstrate DEEPEN, which incorporates dependency parsing into NegEx, can reduce the number of incorrect negation assignment for patients with positive findings, and therefore improve the identification of patients with the target clinical findings in EHRs. PMID:25791500
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Kokoski, R J; Jain, M
1975-03-01
Radioimmunoassay (RIA) and thin-layer chromatography (TLC) were compared for morphine detection in an actual narcotic clinic setting. A choice of urines from all those screened by TLC allowed a critical comparison as to actual use or non-use of narcotic drugs, rather than a sampling at random in which the question of possible false positives or negatives cannot be conclusively answered. Although RIA is more sensitive than TLC, its advantage is apparent only in those cases where urine specimens are difficult to obtain frequently regularly or where the use of morphine is suspected by the positive identification of quinine in urine that was morphine-negative by TLC. In a selected group of negative and positive specimens chosen without conscious bias, the two methods gave consistently similar results, indicating that the modified TLC method provided a few or no false positives or negatives if the negatives were from those cases that were not positive anytime up to 3-4 days before urine collection. We conclude that RIA can be of significant value as a supplement to a TLC screening program, without sacrificing the many advantages that TLC has to offer.
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Wu, Hu-bing; Wang, Lijuan; Wang, Quan-shi; Han, Yan-jian; Li, Hong-sheng; Zhou, Wen-lan; Tian, Ying
2015-01-01
Purpose. The present study investigated which type of adenocarcinoma with BAC features was prone to be false-negative on 18F-FDG PET/CT. Materials and Methods. A retrospective study was performed on 51 consecutive patients with localized adenocarcinoma with BAC features. CT and PET were assessed for lesion size, GGO percentage, and SUVmax. Lesions with FDG uptake the same as or more than mediastinal blood-pool activity were considered as PET-positive. Results. Of the 51 cases, 19.6% presented as pure GGO nodules, 31.4% as mixed nodules, and 49.0% as solid nodules. None of the pure GGO nodules was 18F-FDG avid, compared with 37.5% of mixed nodules and 96.0% of solid nodules (χ 2 = 31.55, P = 0.000). In the mixed nodule group, SUVmax was negatively correlated with GGO percentage (r = −0.588; P = 0.021). The positive detection rate of 18F-FDG PET/CT was 50.0%, 55.6%, and 100% in tumors 1.1–2.0 cm, 2.1–3.0 cm, and >3.0 cm in diameter, respectively (χ 2 = 5.815, P = 0.055). General linear model factor analysis showed that the GGO was an important factor contributing to false-negative PET/CT results (F = 23.992, P = 0.000), but lesion size was not (F = 0.602, P = 0.866). Conclusions. The present study indicated that the adenocarcinoma with BAC features presented as nonsolid nodule is prone to be false negative on 18F-FDG PET/CT. PMID:25879020
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Sun, Yong-sheng; Lou, Si-quan; Wen, Jian-min; Lv, Wei-xin; Jiao, Chang-geng; Yang, Su-min; Xu, Hai-bin
2011-02-01
To assess the clinical value of polymerase chain reaction (PCR) in the diagnosis and differential diagnosis of joint tuberculosis (TB). PCR was used blindly to detect the DNA of Mycobacterium tuberculosis (M.TB) in five specimens of M.TB, 5 of BCG, and 10 of other bacteria. Then, M. TB in 98 samples from patients with joint TB and 100 samples from patients with non-tubercular joint disorders were detected by PCR, acid-fast staining and culture,. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of PCR were calculated. The χ2 test was used for statistical analysis of the frequency of various factors. At the same time, some problems with PCR were also systematically analyzed. (1) In the "standard samples", both M. TB and BCG showed positive while other bacteria were negative. (2) In 98 cases from patients with joint TB, 81 were positive by PCR, 6 by acid-fast staining, and 17 by culture. In 100 cases from patients with non-tuberculous joint disorders, 9 were positive by PCR, and none by either acid-fast staining or culture. Sensitivity, specificity, accuracy, positive and negative predictive value of PCR were 82.65% (81/98), 91.00% (91/100), 86.87% (172/198), 90.00% (81/90) and 84.26% (91/108), respectively. (3) The positive rates for PCR, acid-fast staining and culture in detection of M. TB were 82.65% (81/98), 6.12% (6/98), and 17.34% (17/98), respectively. There were statistically significant differences between the three methods (P < 0.001). (4) The process of PCR is automatic, and can be completed within 3 to 6 hours, whereas 4 to 8 weeks are required for the conventional culture of M. TB. PCR is a sensitive, specific, rapid, simple and minimally invasive method for detection of M. TB in samples from joint TB, and can play an important role in early and rapid diagnosis and differential diagnosis of joint TB. But it also has some limitations, such as false positivity and false negativity. © 2011 Tianjin Hospital and Blackwell Publishing Asia Pty Ltd.
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Affect influences false memories at encoding: evidence from recognition data.
Storbeck, Justin; Clore, Gerald L
2011-08-01
Memory is susceptible to illusions in the form of false memories. Prior research found, however, that sad moods reduce false memories. The current experiment had two goals: (1) to determine whether affect influences retrieval processes, and (2) to determine whether affect influences the strength and the persistence of false memories. Happy or sad moods were induced either before or after learning word lists designed to produce false memories. Control groups did not experience a mood induction. We found that sad moods reduced false memories only when induced before learning. Signal detection analyses confirmed that sad moods induced prior to learning reduced activation of nonpresented critical lures suggesting that they came to mind less often. Affective states, however, did not influence retrieval effects. We conclude that negative affective states promote item-specific processing, which reduces false memories in a similar way as using an explicitly guided cognitive control strategy. 2011 APA, all rights reserved
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Affect Influences False Memories at Encoding: Evidence from Recognition Data
Storbeck, Justin; Clore, Gerald L.
2014-01-01
Memory is susceptible to illusions in the form of false memories. Prior research found, however, that sad moods reduce false memories. The current experiment had two goals: (1) to determine whether affect influences retrieval processes, and (2) to determine whether affect influences the strength and the persistence of false memories. Happy or sad moods were induced either before or after learning word lists designed to produce false memories. Control groups did not experience a mood induction. We found that sad moods reduced false memories only when induced before learning. Signal detection analyses confirmed that sad moods induced prior to learning reduced activation of nonpresented critical lures suggesting that they came to mind less often. Affective states, however, did not influence retrieval effects. We conclude that negative affective states promote item-specific processing, which reduces false memories in a similar way as using an explicitly guided cognitive control strategy. PMID:21517165
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A source-attractor approach to network detection of radiation sources
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wu, Qishi; Barry, M. L..; Grieme, M.
Radiation source detection using a network of detectors is an active field of research for homeland security and defense applications. We propose Source-attractor Radiation Detection (SRD) method to aggregate measurements from a network of detectors for radiation source detection. SRD method models a potential radiation source as a magnet -like attractor that pulls in pre-computed virtual points from the detector locations. A detection decision is made if a sufficient level of attraction, quantified by the increase in the clustering of the shifted virtual points, is observed. Compared with traditional methods, SRD has the following advantages: i) it does not requiremore » an accurate estimate of the source location from limited and noise-corrupted sensor readings, unlike the localizationbased methods, and ii) its virtual point shifting and clustering calculation involve simple arithmetic operations based on the number of detectors, avoiding the high computational complexity of grid-based likelihood estimation methods. We evaluate its detection performance using canonical datasets from Domestic Nuclear Detection Office s (DNDO) Intelligence Radiation Sensors Systems (IRSS) tests. SRD achieves both lower false alarm rate and false negative rate compared to three existing algorithms for network source detection.« less
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Iacocca, Michael A.; Wang, Jian; Dron, Jacqueline S.; Robinson, John F.; McIntyre, Adam D.; Cao, Henian
2017-01-01
Familial hypercholesterolemia (FH) is a heritable condition of severely elevated LDL cholesterol, caused predominantly by autosomal codominant mutations in the LDL receptor gene (LDLR). In providing a molecular diagnosis for FH, the current procedure often includes targeted next-generation sequencing (NGS) panels for the detection of small-scale DNA variants, followed by multiplex ligation-dependent probe amplification (MLPA) in LDLR for the detection of whole-exon copy number variants (CNVs). The latter is essential because ∼10% of FH cases are attributed to CNVs in LDLR; accounting for them decreases false negative findings. Here, we determined the potential of replacing MLPA with bioinformatic analysis applied to NGS data, which uses depth-of-coverage analysis as its principal method to identify whole-exon CNV events. In analysis of 388 FH patient samples, there was 100% concordance in LDLR CNV detection between these two methods: 38 reported CNVs identified by MLPA were also successfully detected by our NGS method, while 350 samples negative for CNVs by MLPA were also negative by NGS. This result suggests that MLPA can be removed from the routine diagnostic screening for FH, significantly reducing associated costs, resources, and analysis time, while promoting more widespread assessment of this important class of mutations across diagnostic laboratories. PMID:28874442
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Slawson, D C; Bennett, J H; Simon, L J; Herman, J M
1994-04-01
Clinicians who manage women with Papanicolaou (Pap) smears showing atypical squamous cells of undetermined significance (ASCUS) may miss clinically significant cervical disease by repeating the cytology alone. We evaluated the ability of the human papillomavirus (HPV) screen and the naked-eye examination after a cervical acetic acid wash to enhance the follow-up Pap smear in predicting an abnormal colposcopic biopsy. Pap smears were performed on all women (N = 7458) attending six family practice offices for a health maintenance examination from August 1989 through February 1991. Consenting subjects with ASCUS underwent repeat cytological testing, an HPV screen, and a cervical acetic acid wash examination immediately before colposcopy after a 4- to 6-month waiting period. Of the 122 consenting women identified with ASCUS, 67 (55%) demonstrated abnormalities on biopsy, including 26 with condyloma, 26 with cervical intraepithelial neoplasia I (CIN I), and 15 with CIN II to III. The false-negative rate, 58%, of the follow-up Pap smear alone for detecting these cases of condyloma and CIN was significantly decreased (false-negative rate, 27%) with the use of the cervical acetic acid wash as an adjunctive test. There was no additional reduction in the false-negative rate with the use of the HPV screen. Of the 15 subjects with high-grade cervical lesions (CIN II to III), 14 had either an abnormal follow-up Pap smear or an abnormal cervical acetic acid wash examination. Among women with cervical atypia, a single follow-up Pap smear alone failed to detect one third of the cases of high-grade disease. Ninety-three percent of these cases were detected, however, with a follow-up Pap smear and an acetic acid wash. Our one subject with a high-grade lesion missed with this combination of tests had an unsatisfactory Pap smear. Use of both tests together may reliably guide clinical decisions regarding the management of cervical atypia.
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Cousins, A.; Balalis, G. L.; Thompson, S. K.; Forero Morales, D.; Mohtar, A.; Wedding, A. B.; Thierry, B.
2015-01-01
Using magnetic tunnelling junction sensors, a novel magnetometer probe for the identification of the sentinel lymph node using magnetic tracers was developed. Probe performance was characterised in vitro and validated in a preclinical swine model. Compared to conventional gamma probes, the magnetometer probe showed excellent spatial resolution of 4.0 mm, and the potential to detect as few as 5 μg of magnetic tracer. Due to the high sensitivity of the magnetometer, all first-tier nodes were identified in the preclinical experiments, and there were no instances of false positive or false negative detection. Furthermore, these preliminary data encourage the application of the magnetometer probe for use in more complex lymphatic environments, such as in gastrointestinal cancers, where the sentinel node is often in close proximity to other non-sentinel nodes, and high spatial resolution detection is required. PMID:26038833
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Nonlinear ultrasonic fatigue crack detection using a single piezoelectric transducer
NASA Astrophysics Data System (ADS)
An, Yun-Kyu; Lee, Dong Jun
2016-04-01
This paper proposes a new nonlinear ultrasonic technique for fatigue crack detection using a single piezoelectric transducer (PZT). The proposed technique identifies a fatigue crack using linear (α) and nonlinear (β) parameters obtained from only a single PZT mounted on a target structure. Based on the different physical characteristics of α and β, a fatigue crack-induced feature is able to be effectively isolated from the inherent nonlinearity of a target structure and data acquisition system. The proposed technique requires much simpler test setup and less processing costs than the existing nonlinear ultrasonic techniques, but fast and powerful. To validate the proposed technique, a real fatigue crack is created in an aluminum plate, and then false positive and negative tests are carried out under varying temperature conditions. The experimental results reveal that the fatigue crack is successfully detected, and no positive false alarm is indicated.
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Siu, L. Kristopher; Tsai, Yu-Kuo; Lin, Jung-Chung; Chen, Te-Li; Fung, Chang-Phone
2016-01-01
In this study, a novel colloidal gold-based immunochromatographic strip (ICS) containing anti-Klebsiella pneumoniae capsular polysaccharide polyclonal antibodies was developed to specifically detect K. pneumoniae serotypes K1 and K2. Capsular polysaccharide K1 and K2 antigens were first used to produce polyclonal anti-K1 and anti-K2 antibodies. Reference strains with different serotypes, nontypeable K. pneumoniae strains, and other bacterial species were then used to assess the sensitivity and specificity of these test strips. The detection limit was found to be 105 CFU, and the ICSs were stable for 6 months when stored at room temperature. No false-positive or false-negative results were observed, and equivalent results were obtained compared to those of more conventional test methods, such as PCR or serum agglutination. In conclusion, the ICS developed here requires no technical expertise and allows for the specific, rapid, and simultaneous detection of K. pneumoniae serotypes K1 and K2. PMID:27707941
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Detection of human enteric viruses in stream water with RT-PCR and cell culture.
Denis-Mize, K.; Fout, G.S.; Dahling, D.R.; Francy, D.S.
2004-01-01
A multiplex RT-PCR method was used to measure virus occurrence at five stream water sites that span a range of hydroclimatic, water-quality, and land-use characteristics. The performance of the molecular method was evaluated in comparison with traditional cell culture and Escherichia coli membrane filtration assays. The study incorporated multiple quality controls and included a control for virus recovery during the sampling procedure as well as controls to detect potentially false-negative and false-positive data. Poliovirus recovery ranged from 16 to 65% and was variable, even in samples collected within the same stream. All five sites were positive for viruses by both molecular and cell culture-based virus assays. Enteroviruses, reoviruses, rotaviruses, and hepatitis A viruses were detected, but the use of the quality controls proved critical for interpretation of the molecular data. All sites showed evidence of faecal contamination, and culturable viruses were detected in four samples that would have met the US Environmental Protection Agency's recommended E. coli guideline for safe recreational water.
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[Primary cervical cancer screening].
Vargas-Hernández, Víctor Manuel; Vargas-Aguilar, Víctor Manuel; Tovar-Rodríguez, José María
2015-01-01
Cervico-uterine cancer screening with cytology decrease incidence by more than 50%. The cause of this cancer is the human papilloma virus high risk, and requires a sensitive test to provide sufficient sensitivity and specificity for early detection and greater interval period when the results are negative. The test of the human papilloma virus high risk, is effective and safe because of its excellent sensitivity, negative predictive value and optimal reproducibility, especially when combined with liquid-based cytology or biomarkers with viral load, with higher sensitivity and specificity, by reducing false positives for the detection of cervical intraepithelial neoplasia grade 2 or greater injury, with excellent clinical benefits to cervical cancer screening and related infection of human papilloma virus diseases, is currently the best test for early detection infection of human papillomavirus and the risk of carcinogenesis. Copyright © 2015 Academia Mexicana de Cirugía A.C. Published by Masson Doyma México S.A. All rights reserved.
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Gerstl, Sibylle; Dunkley, Sophie; Mukhtar, Ahmed; De Smet, Martin; Baker, Samuel; Maikere, Jacob
2010-01-21
Most malaria rapid diagnostic tests (RDTs) use HRP2 detection, including Paracheck-Pf(R), but their utility is limited by persistent false positivity after treatment. PLDH-based tests become negative more quickly, but sensitivity has been reported below the recommended standard of 90%. A new pLDH test, CareStart three-line P.f/PAN-pLDH, claims better sensitivity with continued rapid conversion to negative. The study aims were to 1) compare sensitivity and specificity of CareStart to Paracheck-Pf(R) to diagnose falciparum malaria in children under five years of age, 2) assess how quickly false-positive CareStart tests become negative and 3) evaluate ease of use and inter-reader agreement of both tests. Participants were included if they were aged between two and 59 months, presenting to a Médecins Sans Frontières community health centre in eastern Sierra Leone with suspected malaria defined as fever (axillary temperature > 37.5 degrees C) and/or history of fever in the previous 72 hours and no signs of severe disease. The same capillary blood was used for the RDTs and the blood slide, the latter used as the gold standard reference. All positive participants were treated with supervised artesunate and amodiaquine treatment for three days. Participants with a persistent false-positive CareStart, but a negative blood slide on Day 2, were followed with repeated CareStart and blood slide tests every seven days until CareStart became negative or a maximum of 28 days. Sensitivity of CareStart was 99.4% (CI 96.8-100.0, 168/169) and of Paracheck-Pf(R), 98.8% (95% CI 95.8-99.8, 167/169). Specificity of CareStart was 96.0% (CI 91.9-98.4, 167/174) and of Paracheck-Pf(R), 74.7% (CI 67.6-81.0, 130/174) (p < 0.001). Neither test showed any change in sensitivity with decreasing parasitaemia. Of the 155 eligible follow-up CareStart participants, 63.9% (99/155) had a false-positive test on day 2, 21.3% (33/155) on day 7, 5.8% (9/155) on day 14, 1.9% (3/155) on day 21 and 0.6% (1/155) on day 28. The median time for test negativity was seven days. CareStart was as easy to use and interpret as Paracheck-Pf(R) with excellent inter-reader agreement. Both RDTs were highly sensitive, met WHO standards for the detection of falciparum malaria monoinfections where parasitaemia was >100 parasites/mul and were easy to use. CareStart persistent false positivity decreased quickly after successful anti-malarial treatment, making it a good choice for a RDT for a hyperendemic falciparum malaria area.
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Rovira, Ericka; Parasuraman, Raja
2010-06-01
This study examined whether benefits of conflict probe automation would occur in a future air traffic scenario in which air traffic service providers (ATSPs) are not directly responsible for freely maneuvering aircraft but are controlling other nonequipped aircraft (mixed-equipage environment). The objective was to examine how the type of automation imperfection (miss vs. false alarm) affects ATSP performance and attention allocation. Research has shown that the type of automation imperfection leads to differential human performance costs. Participating in four 30-min scenarios were 12 full-performance-level ATSPs. Dependent variables included conflict detection and resolution performance, eye movements, and subjective ratings of trust and self confidence. ATSPs detected conflicts faster and more accurately with reliable automation, as compared with manual performance. When the conflict probe automation was unreliable, conflict detection performance declined with both miss (25% conflicts detected) and false alarm automation (50% conflicts detected). When the primary task of conflict detection was automated, even highly reliable yet imperfect automation (miss or false alarm) resulted in serious negative effects on operator performance. The further in advance that conflict probe automation predicts a conflict, the greater the uncertainty of prediction; thus, designers should provide users with feedback on the state of the automation or other tools that allow for inspection and analysis of the data underlying the conflict probe algorithm.
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Chan, Ta-Chien; Teng, Yung-Chu; Hwang, Jing-Shiang
2015-02-21
Emerging novel influenza outbreaks have increasingly been a threat to the public and a major concern of public health departments. Real-time data in seamless surveillance systems such as health insurance claims data for influenza-like illnesses (ILI) are ready for analysis, making it highly desirable to develop practical techniques to analyze such readymade data for outbreak detection so that the public can receive timely influenza epidemic warnings. This study proposes a simple and effective approach to analyze area-based health insurance claims data including outpatient and emergency department (ED) visits for early detection of any aberrations of ILI. The health insurance claims data during 2004-2009 from a national health insurance research database were used for developing early detection methods. The proposed approach fitted the daily new ILI visits and monitored the Pearson residuals directly for aberration detection. First, negative binomial regression was used for both outpatient and ED visits to adjust for potentially influential factors such as holidays, weekends, seasons, temporal dependence and temperature. Second, if the Pearson residuals exceeded 1.96, aberration signals were issued. The empirical validation of the model was done in 2008 and 2009. In addition, we designed a simulation study to compare the time of outbreak detection, non-detection probability and false alarm rate between the proposed method and modified CUSUM. The model successfully detected the aberrations of 2009 pandemic (H1N1) influenza virus in northern, central and southern Taiwan. The proposed approach was more sensitive in identifying aberrations in ED visits than those in outpatient visits. Simulation studies demonstrated that the proposed approach could detect the aberrations earlier, and with lower non-detection probability and mean false alarm rate in detecting aberrations compared to modified CUSUM methods. The proposed simple approach was able to filter out temporal trends, adjust for temperature, and issue warning signals for the first wave of the influenza epidemic in a timely and accurate manner.
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Mahan, S M; Tebele, N; Mukwedeya, D; Semu, S; Nyathi, C B; Wassink, L A; Kelly, P J; Peter, T; Barbet, A F
1993-01-01
Heartwater, a major constraint to improved livestock production in Zimbabwe, threatens to invade areas which have been previously unaffected. To monitor its spread in Zimbabwe, an immunoblotting diagnostic assay based on the responses of animals to the immunodominant, conserved 32-kDa protein of Cowdria ruminantium was evaluated. In this assay, no false reactions were detected with sera known to be positive and negative, but sera from some cattle, sheep, and goats from heartwater-free areas of Zimbabwe reacted strongly with the 32-kDa protein, suggesting that either these animals had previous exposure to heartwater or they were false positives. To investigate the possibility of previous exposure to heartwater, 11 immunoblot-positive and 6 immunoblot-negative sheep from heartwater-free areas of Zimbabwe were compared regarding their susceptibilities to challenge with C. ruminantium. Prior to challenge, C. ruminantium could not be detected in any sheep by transmission to Amblyomma hebraeum ticks or by the polymerase chain reaction (PCR) conducted with plasma samples. All sheep were equally susceptible to the challenge, and infection was confirmed by brain biopsy, necropsy, PCR, and transmission of C. ruminantium to ticks. Our data suggest that the immunoblot-positive reactions of sera from heartwater-free areas were due not to previous C. ruminantium infection but rather to antigenic cross-reactivity between C. ruminantium and another agent(s) such as Ehrlichia species. In conclusion, the immunodominant 32-kDa protein is not antigenically specific to C. ruminantium and its use in serological diagnosis of heartwater requires reevaluation. Images PMID:8253974
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Tham, Jill M.; Lee, Szu Hee; Tan, Theresa M. C.; Ting, Robert C. Y.; Kara, Ursula A. K.
1999-01-01
A rapid procedure for the diagnosis of malaria infections directly from dried blood spots by PCR amplification was evaluated with samples from 52 patients. Plasmodium infections were identified with a genus-specific primer set, and species differentiation between Plasmodium falciparum and Plasmodium vivax was analyzed by multiplex PCR. The PCR test with any of the three primer sets was able to detect as few as four parasites per microliter by gel electrophoresis or by nonisotopic paper hybridization chromatography. The diagnoses obtained by PCR correlated closely with those obtained by Giemsa staining except for two samples observed to have mixed P. falciparum-P. vivax infections. These were initially missed by microscopic analysis. In comparison with antigen-capture assays for P. falciparum, the PCR assays were able to detect three infections that were missed by the ParaSight-F test. The PCR test was negative for nine ParaSight-F-positive samples and one ICT Malaria Pf-positive sample, and these were confirmed to be false-positive results. The PCR thus gave no false-negative or false-positive results. Patients undergoing antimalarial therapy were also monitored by the PCR assay. Four of seven patients who were PCR positive for P. vivax at the time of discharge were later readmitted to the hospital with a recurrence of P. vivax infection. We would like to propose that PCR is a sensitive and easy method that can serve as a useful addition to microscopy for the diagnosis and the clinical monitoring of treatment of malaria. PMID:10203469
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Landry, Marie L.; Eid, Tore; Bannykh, Serguei; Major, Eugene
2009-01-01
Genome amplification methods such as polymerase chain reaction (PCR) have revolutionized our ability to detect viruses in spinal fluids of patients with neurologic diseases. It is not as well appreciated among clinicians that PCR protocols, quality assurance, and technical expertise vary significantly among laboratories. In a multi-laboratory blinded study of herpes simplex virus PCR, the most widely used and best validated CSF PCR assay, low-level positives were often missed and false positives were not uncommon [Schloss L, van Loon AM, Cinque P, Cleator G, Echevarria JM, Falk KI, et al. An international external quality assessment of nucleic acid amplification of herpes simplex virus. J Clin Virol 2003;28(2):175–85]. In addition, genome variability and mutations, which are increasingly recognized for a number of different viruses, can lead to falsely low or negative results. Both clinicians and laboratories must recognize the limitations of PCR, since misleading results may have serious consequences. We present here a case of a rapidly progressive, fatal neurologic illness in a young mother, whose CSF JCV DNA PCR at a reference laboratory was falsely negative. Ultimately, brain biopsy established the diagnosis of progressive multifocal leukoencephalopathy (PML). Repeat PCR testing of the same CSF targeting a different region of the genome yielded a high positive result. PMID:18701345
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El-Sayed, Abdulrahman M.; Lauderdale, Diane S.; Galea, Sandro
2010-01-01
Objective Data about Arab-Americans, a growing ethnic minority, is not routinely collected in vital statistics, registry, or administrative data in the US. The difficulty in identifying Arab-Americans using publicly available data sources is a barrier to health research about this group. Here, we validate an empirically-based, probabilistic Arab name algorithm (ANA) for identifying Arab-Americans in health research. Design We used data from all Michigan birth certificates between 2000-2005. Fathers’ surnames and mothers’ maiden names were coded as Arab or non-Arab according to the ANA. We calculated sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) of Arab ethnicity inferred using the ANA as compared to self-reported Arab ancestry. Results State-wide, the ANA had a specificity of 98.9%, a sensitivity of 50.3%, a PPV of 57.0%, and a NPV of 98.6%. Both the false positive and false negative rates were higher among men than among women. As the concentration of Arab-Americans in a study locality increased, the ANA false positive rate increased and false-negative rate decreased. Conclusion The ANA is highly specific but only moderately sensitive as a means of detecting Arab ancestry. Future research should compare health characteristics among Arab-American populations defined by Arab ancestry and those defined by the ANA. PMID:20845117
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Levenback, Charles F.; Ali, Shamshad; Coleman, Robert L.; Gold, Michael A.; Fowler, Jeffrey M.; Judson, Patricia L.; Bell, Maria C.; De Geest, Koen; Spirtos, Nick M.; Potkul, Ronald K.; Leitao, Mario M.; Bakkum-Gamez, Jamie N.; Rossi, Emma C.; Lentz, Samuel S.; Burke, James J.; Van Le, Linda; Trimble, Cornelia L.
2012-01-01
Purpose To determine the safety of sentinel lymph node biopsy as a replacement for inguinal femoral lymphadenectomy in selected women with vulvar cancer. Patients and Methods Eligible women had squamous cell carcinoma, at least 1-mm invasion, and tumor size ≥ 2 cm and ≤ 6 cm. The primary tumor was limited to the vulva, and there were no groin lymph nodes that were clinically suggestive of cancer. All women underwent intraoperative lymphatic mapping, sentinel lymph node biopsy, and inguinal femoral lymphadenectomy. Histologic ultra staging of the sentinel lymph node was prescribed. Results In all, 452 women underwent the planned procedures, and 418 had at least one sentinel lymph node identified. There were 132 node-positive women, including 11 (8.3%) with false-negative nodes. Twenty-three percent of the true-positive patients were detected by immunohistochemical analysis of the sentinel lymph node. The sensitivity was 91.7% (90% lower confidence bound, 86.7%) and the false-negative predictive value (1-negative predictive value) was 3.7% (90% upper confidence bound, 6.1%). In women with tumor less than 4 cm, the false-negative predictive value was 2.0% (90% upper confidence bound, 4.5%). Conclusion Sentinel lymph node biopsy is a reasonable alternative to inguinal femoral lymphadenectomy in selected women with squamous cell carcinoma of the vulva. PMID:22753905
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Zhang, Xi; Lin, Xi; Tan, Yanjuan; Zhu, Ying; Wang, Hui; Feng, Ruimei; Tang, Guoxue; Zhou, Xiang; Li, Anhua; Qiao, Youlin
2018-04-01
The automated breast ultrasound system (ABUS) is a potential method for breast cancer detection; however, its diagnostic performance remains unclear. We conducted a hospital-based multicenter diagnostic study to evaluate the clinical performance of the ABUS for breast cancer detection by comparing it to handheld ultrasound (HHUS) and mammography (MG). Eligible participants underwent HHUS and ABUS testing; women aged 40-69 years additionally underwent MG. Images were interpreted using the Breast Imaging Reporting and Data System (BI-RADS). Women in the BI-RADS categories 1-2 were considered negative. Women classified as BI-RADS 3 underwent magnetic resonance imaging to distinguish true- and false-negative results. Core aspiration or surgical biopsy was performed in women classified as BI-RADS 4-5, followed by a pathological diagnosis. Kappa values and agreement rates were calculated between ABUS, HHUS and MG. A total of 1,973 women were included in the final analysis. Of these, 1,353 (68.6%) and 620 (31.4%) were classified as BI-RADS categories 1-3 and 4-5, respectively. In the older age group, the agreement rate and Kappa value between the ABUS and HHUS were 94.0% and 0.860 (P<0.001), respectively; they were 89.2% and 0.735 (P<0.001) between the ABUS and MG, respectively. Regarding consistency between imaging and pathology results, 78.6% of women classified as BI-RADS 4-5 based on the ABUS were diagnosed with precancerous lesions or cancer; which was 7.2% higher than that of women based on HHUS. For BI-RADS 1-2, the false-negative rates of the ABUS and HHUS were almost identical and were much lower than those of MG. We observed a good diagnostic reliability for the ABUS. Considering its performance for breast cancer detection in women with high-density breasts and its lower operator dependence, the ABUS is a promising option for breast cancer detection in China.
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Kozycki, Christina T; Umulisa, Noella; Rulisa, Stephen; Mwikarago, Emil I; Musabyimana, Jean Pierre; Habimana, Jean Pierre; Karema, Corine; Krogstad, Donald J
2017-03-20
Rapid diagnostic tests (RDTs) for histidine rich protein 2 (HRP2) are often used to determine whether persons with fever should be treated with anti-malarials. However, Plasmodium falciparum parasites with a deletion of the hrp2 gene yield false-negative RDTs and there are concerns the sensitivity of HRP2-based RDTs may fall when the intensity of transmission decreases. This observational study enrolled 9226 patients at three health centres in Rwanda from April 2014 to April 2015. It then compared the sensitivity of RDTs based on HRP2 and the Plasmodium lactate dehydrogenase (pLDH) to microscopy (thick smears) for the diagnosis of malaria. PCR was used to determine whether deletions of the histidine-rich central repeat region of the hrp2 gene (exon 2) were associated with false-negative HRP2-based RDTs. In comparison to microscopy, the sensitivity and specificity of HRP2- and pLDH-based RDTs were 89.5 and 86.2% and 80.2 and 94.3%, respectively. When the results for both RDTs were combined, sensitivity rose to 91.8% and specificity was 85.7%. Additionally, when smear positivity fell from 46 to 3%, the sensitivity of the HRP2-based RDT fell from 88 to 67%. Of 370 samples with false-negative HRP2 RDT results for which PCR was performed, 140 (38%) were identified as P. falciparum by PCR. Of the isolates identified as P. falciparum by PCR, 32 (23%) were negative for the hrp2 gene based on PCR. Of the 32 P. falciparum isolates negative for hrp2 by PCR, 17 (53%) were positive based on the pLDH RDT. This prospective study of RDT performance coincided with a decline in the intensity of malaria transmission in Kibirizi (fall in slide positivity from 46 to 3%). This decline was associated with a decrease in HRP2 RDT sensitivity (from 88 to 67%). While P. falciparum isolates without the hrp2 gene were an important cause of false-negative HRP2-based RDTs, most were identified by the pLDH-based RDT. Although WHO does not recommend the use of combined HRP2/pLDH testing in sub-Saharan Africa, these results suggest that combination HRP2/pLDH-based RDTs could reduce the impact of false-negative HRP2-based RDTs for detection of symptomatic P. falciparum malaria.
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Identifying QT prolongation from ECG impressions using a general-purpose Natural Language Processor
Denny, Joshua C.; Miller, Randolph A.; Waitman, Lemuel Russell; Arrieta, Mark; Peterson, Joshua F.
2009-01-01
Objective Typically detected via electrocardiograms (ECGs), QT interval prolongation is a known risk factor for sudden cardiac death. Since medications can promote or exacerbate the condition, detection of QT interval prolongation is important for clinical decision support. We investigated the accuracy of natural language processing (NLP) for identifying QT prolongation from cardiologist-generated, free-text ECG impressions compared to corrected QT (QTc) thresholds reported by ECG machines. Methods After integrating negation detection to a locally-developed natural language processor, the KnowledgeMap concept identifier, we evaluated NLP-based detection of QT prolongation compared to the calculated QTc on a set of 44,318 ECGs obtained from hospitalized patients. We also created a string query using regular expressions to identify QT prolongation. We calculated sensitivity and specificity of the methods using manual physician review of the cardiologist-generated reports as the gold standard. To investigate causes of “false positive” calculated QTc, we manually reviewed randomly selected ECGs with a long calculated QTc but no mention of QT prolongation. Separately, we validated the performance of the negation detection algorithm on 5,000 manually-categorized ECG phrases for any medical concept (not limited to QT prolongation) prior to developing the NLP query for QT prolongation. Results The NLP query for QT prolongation correctly identified 2,364 of 2,373 ECGs with QT prolongation with a sensitivity of 0.996 and a positive predictive value of 1.000. There were no false positives. The regular expression query had a sensitivity of 0.999 and positive predictive value of 0.982. In contrast, the positive predictive value of common QTc thresholds derived from ECG machines was 0.07–0.25 with corresponding sensitivities of 0.994–0.046. The negation detection algorithm had a recall of 0.973 and precision of 0.982 for 10,490 concepts found within ECG impressions. Conclusions NLP and regular expression queries of cardiologists’ ECG interpretations can more effectively identify QT prolongation than the automated QTc intervals reported by ECG machines. Future clinical decision support could employ NLP queries to detect QTc prolongation and other reported ECG abnormalities. PMID:18938105
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Reducing False Positives in Runtime Analysis of Deadlocks
NASA Technical Reports Server (NTRS)
Bensalem, Saddek; Havelund, Klaus; Clancy, Daniel (Technical Monitor)
2002-01-01
This paper presents an improvement of a standard algorithm for detecting dead-lock potentials in multi-threaded programs, in that it reduces the number of false positives. The standard algorithm works as follows. The multi-threaded program under observation is executed, while lock and unlock events are observed. A graph of locks is built, with edges between locks symbolizing locking orders. Any cycle in the graph signifies a potential for a deadlock. The typical standard example is the group of dining philosophers sharing forks. The algorithm is interesting because it can catch deadlock potentials even though no deadlocks occur in the examined trace, and at the same time it scales very well in contrast t o more formal approaches to deadlock detection. The algorithm, however, can yield false positives (as well as false negatives). The extension of the algorithm described in this paper reduces the amount of false positives for three particular cases: when a gate lock protects a cycle, when a single thread introduces a cycle, and when the code segments in different threads that cause the cycle can actually not execute in parallel. The paper formalizes a theory for dynamic deadlock detection and compares it to model checking and static analysis techniques. It furthermore describes an implementation for analyzing Java programs and its application to two case studies: a planetary rover and a space craft altitude control system.
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Lam, Alice D; Zepeda, Rodrigo; Cole, Andrew J; Cash, Sydney S
2016-10-01
Decades of experience with intracranial recordings in patients with epilepsy have demonstrated that seizures can occur in deep cortical regions such as the mesial temporal lobes without showing any obvious signs of seizure activity on scalp electroencephalogram. Predicated on the idea that these seizures are purely focal, currently, the only way to detect these 'scalp-negative seizures' is with intracranial recordings. However, intracranial recordings are only rarely performed in patients with epilepsy, and are almost never performed outside of the context of epilepsy. As such, little is known about scalp-negative seizures and their role in the natural history of epilepsy, their effect on cognitive function, and their association with other neurological diseases. Here, we developed a novel approach to non-invasively identify scalp-negative seizures arising from the mesial temporal lobe based on scalp electroencephalogram network connectivity measures. We identified 25 scalp-negative mesial temporal lobe seizures in 10 patients and obtained control records from an additional 13 patients, all of whom underwent recordings with foramen ovale electrodes and scalp electroencephalogram. Scalp data from these records were used to train a scalp-negative seizure detector, which consisted of a pair of logistic regression classifiers that used scalp electroencephalogram coherence properties as input features. On cross-validation performance, this detector correctly identified scalp-negative seizures in 40% of patients, and correctly identified the side of seizure onset for each seizure detected. In comparison, routine clinical interpretation of these scalp electroencephalograms failed to identify any of the scalp-negative seizures. Among the patients in whom the detector raised seizure alarms, 80% had scalp-negative mesial temporal lobe seizures. The detector had a false alarm rate of only 0.31 per day and a positive predictive value of 75%. Of the 13 control patients, false seizure alarms were raised in only one patient. The fact that our detector specifically recognizes focal mesial temporal lobe seizures based on scalp electroencephalogram coherence features, lends weight to the hypothesis that even focal seizures are a network phenomenon that involve widespread neural connectivity. Our scalp-negative seizure detector has clear clinical utility in patients with temporal lobe epilepsy, and its potential easily translates to other neurological disorders, such as Alzheimer's disease, in which occult mesial temporal lobe seizures are suspected to play a significant role. Importantly, our work establishes a novel approach of using computational approaches to non-invasively detect deep seizure activity, without the need for invasive intracranial recordings. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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USDA-ARS?s Scientific Manuscript database
The use of reverse transcriptase polymerase chain reaction (RT-PCR) or other molecular diagnostic methods is commonly used for the primary diagnosis of Newcastle disease virus (NDV). However, NDV in nature has a range of virulence, and the low virulence viruses must be differentiated from virulent ...
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USDA-ARS?s Scientific Manuscript database
Lactose broth (LB) and buffered peptone (BP) are used as pre-enrichment media to recover Salmonella from feed. Bacterial utilization of feed carbohydrates results in the production of acidic byproducts causing a drop in the media pH which can injure or kill Salmonella and yield false negative resul...
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Hillemann, D; Rüsch-Gerdes, S; Richter, E
2005-12-01
The usefulness of a low-tech rapid test for culture confirmation of Mycobacterium tuberculosis complex, Capilia TB, was tested on 172 mycobacteria-positive clinical samples. The overall sensitivity and specificity were 92.4% and 100%, respectively. In three of nine false-negative isolates a mutation in the mpb64 gene could be detected.
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STFT or CWT for the detection of Doppler ultrasound embolic signals.
Gonçalves, Ivo B; Leiria, Ana; Moura, M M M
2013-09-01
Aiming reliable detection and localization of cerebral blood flow and emboli, embolic signals were added to simulated middle cerebral artery Doppler signals and analysed. Short-time Fourier transform (STFT) and continuous wavelet transform (CWT) were used in the evaluation. The following parameters were used in this study: the powers of the embolic signals added were 5, 6, 6.5, 7, 7.5, 8 and 9 dB; the mother wavelets for CWT analysis were Morlet, Mexican hat, Meyer, Gaussian (order 4) and Daubechies (orders 4 and 8); and the thresholds for detection (equated in terms of false positive, false negative and sensitivity) were 2 and 3.5 dB for the CWT and STFT, respectively. The results indicate that although the STFT allows accurately detecting emboli, better time localization can be achieved with the CWT. Among the CWT, the current best overall results were obtained with Mexican Hat mother wavelet, with optimal results for sensitivity (100% detection rate) for nearly all emboli power values studied. Copyright © 2013 John Wiley & Sons, Ltd.
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Lower Cutoffs for LC-MS/MS Urine Drug Testing Indicates Better Patient Compliance.
Krock, Kevin; Pesce, Amadeo; Ritz, Dennis; Thomas, Richard; Cua, Agnes; Rogers, Ryan; Lipnick, Phil; Kilbourn, Kristen
2017-11-01
Urine drug testing is used by health care providers to determine a patient's compliance to their prescribed regimen and to detect non-prescribed medications and illicit drugs. However, the cutoff levels used by clinical labs are often arbitrarily set and may not reflect the urine drug concentrations of compliant patients. Our aim was to test the hypothesis that commonly used cutoffs for many prescribed and illicit drugs were set too high, and methods using these cutoffs may yield a considerable number of false-negative results. The goals of this study were to outline the way to analyze patient results and estimate a more appropriate cutoff, develop and validate a high sensitivity analytical method capable of quantitating drugs and metabolites at lower than the commonly used cutoffs, and determine the number of true positive results that would have been missed when using the common cutoffs. This was a retrospective study of urine specimens submitted for urine drug testing as part of the monitoring of prescription drug compliance described in chronic opioid therapy treatment guidelines. The study was set in a clinical toxicology laboratory, using specimens submitted for routine analysis by health care providers in the normal course of business. Lognormal distributions of test results were generated and fitted with a trendline to estimate the required cutoff level necessary to capture the normal distributions of each drug for the patient population study. A validated laboratory derived liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis capable of achieving the required cutoff levels was developed for each drug and/or metabolite. The study shows that a lognormal distribution of patient urine test results fitted with a trendline is appropriate for estimating the required cutoff levels needed to assess medication adherence. The study showed a wide variation in the false-negative rate, ranging from 1.5% to 94.3% across a range of prescribed and illicit drugs. The patient specimens were largely sourced from patients in either a long-term pain management program or in treatment for substance use disorder in the US. These specimens may not be representative of patients in other types of treatment or in countries with different approaches to these issues. The high-sensitivity method reduces false-negative results which could negatively impact patient care. Clinicians using less sensitive methods for detecting and quantifying drugs and metabolites in urine should exercise caution in assessing patient adherence using and changing the treatment plan based on those results. Urine drug testing, patient adherence, clinical toxicology, immunoassay, LC-MS, definitive drug testing, REMS, negative test results, false negative.
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The false-negative rate of sentinel node biopsy in patients with breast cancer: a meta-analysis
Pesek, Sarah; Ashikaga, Taka; Krag, Lars Erik; Krag, David
2012-01-01
Background/Purpose In sentinel node surgery for breast cancer, procedural accuracy is assessed by calculating the false-negative rate. It is important to measure this since there are potential adverse outcomes from missing node metastases. We performed a meta-analysis of published data to assess which method has achieved the lowest false-negative rate. Methods We found 3588 articles concerning sentinel nodes and breast cancer published from 1993 through mid-2011; 183 articles met our inclusion criteria. The studies described in these 183 articles included a total of 9306 patients. We grouped the studies by injection material and injection location. The false-negative rates were analyzed according to these groupings and also by the year in which the articles were published. Results There was significant variation in the false-negative rate over time with a trend to higher rates over time. There was significant variation related to injection material. The use of blue dye alone was associated with the highest false-negative rate. Inclusion of a radioactive tracer along with blue dye resulted in a significantly lower false-negative rate. Although there were variations in the false-negative rate according to injection location, none were significant. This meta-analysis also indicates a significant change over time in the false-negative rate. Discussion/Conclusions The use of blue dye should be accompanied by a radioactive tracer to achieve a significantly lower false-negative rate. Location of injection did not have a significant impact on the false-negative rate. Given the limitations of acquiring appropriate data, the false-negative rate should not be used as a metric for training or quality control. PMID:22569745
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Savic, Spasenija; Diebold, Joachim; Zimmermann, Anne-Katrin; Jochum, Wolfram; Baschiera, Betty; Grieshaber, Susanne; Tornillo, Luigi; Bisig, Bettina; Kerr, Keith; Bubendorf, Lukas
2015-08-01
Immunohistochemistry (IHC) has become a promising method for pre-screening ALK-rearrangements in non-small cell lung carcinomas (NSCLC). Various ALK antibodies, detection systems and automated immunostainers are available. We therefore aimed to compare the performance of the monoclonal 5A4 (Novocastra, Leica) and D5F3 (Cell Signaling, Ventana) antibodies using two different immunostainers. Additionally we analyzed the accuracy of prospective ALK IHC-testing in routine diagnostics. Seventy-two NSCLC with available ALK FISH results and enriched for FISH-positive carcinomas were retrospectively analyzed. IHC was performed on BenchMarkXT (Ventana) using 5A4 and D5F3, respectively, and additionally with 5A4 on Bond-MAX (Leica). Data from our routine diagnostics on prospective ALK-testing with parallel IHC, using 5A4, and FISH were available from 303 NSCLC. All three IHC protocols showed congruent results. Only 1/25 FISH-positive NSCLC (4%) was false negative by IHC. For all three IHC protocols the sensitivity, specificity, positive (PPV) and negative predictive values (NPV) compared to FISH were 96%, 100%, 100% and 97.8%, respectively. In the prospective cohort 3/32 FISH-positive (9.4%) and 2/271 FISH-negative (0.7%) NSCLC were false negative and false positive by IHC, respectively. In routine diagnostics the sensitivity, specificity, PPV and NPV of IHC compared to FISH were 90.6%, 99.3%, 93.5% and 98.9%, respectively. 5A4 and D5F3 are equally well suited for detecting ALK-rearranged NSCLC. BenchMark and BOND-MAX immunostainers can be used for IHC with 5A4. True discrepancies between IHC and FISH results do exist and need to be addressed when implementing IHC in an ALK-testing algorithm. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
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Meiklejohn, D J; Ridley, L J; Ngu, M C; Cowlishaw, J L; Duller, A; Ridley, W
2018-06-11
Colorectal cancers result in substantial morbidity and mortality to Australian society each year. The usual investigation for bowel malignancyis optical colonoscopy (OC), withcomputed tomographic colonography (CTC) used as an alternative investigation. The catharsis and colon insufflation associated with these investigations pose a higher risk in the elderly and frail. Risks include perforation, serum electrolyte disturbance, and anaesthesia/sedation risks.Minimal preparation computed tomographic colonography (MPCTC) eliminates these risks. This paper audits a 6-year period ofMPCTC in an Australian tertiary referral hospital. 145 patients underwent MPCTC during the study period. There were 7 true positives, 2 false positives and 2 false negatives. Analysis of this population indicates a sensitivity of 0.78 (95% CI 0.51 - 1.05), specificity of 0.99 (95% CI 0.97 - 1.01), positive predictive value (PPV) of 0.78 (95% CI 0.51 - 1.05) and negative predictive value (NPV) of 0.99 (95% CI 0.97 - 1.01). These findings are concordant with other published studies. The auditconfirmsthatminimal preparation CT colonography is a reasonable alternative to OC and CTC in detecting colorectal cancer in symptomatic elderly and frail patients, without the procedural risks inherent inmore invasive investigations. For most patients MPCTC ruled out significant colorectal carcinoma with a high negative predictive value. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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Added Value of Contrast-Enhanced Spectral Mammography in Postscreening Assessment.
Tardivel, Anne-Marie; Balleyguier, Corinne; Dunant, Ariane; Delaloge, Suzette; Mazouni, Chafika; Mathieu, Marie-Christine; Dromain, Clarisse
2016-09-01
To assess the value on diagnostic and treatment management of contrast-enhanced spectral mammography (CESM), as adjunct to mammography (MG) and ultrasound (US) in postscreening in a breast cancer unit for patients with newly diagnosed breast cancer or with suspicious findings on conventional imaging. Retrospective review of routine use of bilateral CESM performed between September 2012 and September 2013 in 195 women with suspicious or undetermined findings on MG and/or US. CESM images were blindly reviewed by two radiologists for BI-RADS(®) assessment and probability of malignancy. Each lesion was definitely confirmed either with histopathology or follow-up. Two hundred and ninety-nine lesions were detected (221 malignant). CESM sensitivity, specificity, positive-predictive value and negative-predictive value were 94% (CI: 89-96%), 74% (CI: 63-83%), 91% (CI: 86-94%) and 81% (CI: 70-89%), respectively, with 18 false positive and 14 false negative. CESM changed diagnostic and treatment strategy in 41 (21%) patients either after detection of additional malignant lesions in 38 patients (19%)-with a more extensive surgery (n = 21) or neo-adjuvant chemotherapy (n = 1)-or avoiding further biopsy for 20 patients with negative CESM. CESM can be performed easily in a clinical assessment after positive breast cancer screening and may change significantly the diagnostic and treatment strategy through breast cancer staging. © 2016 Wiley Periodicals, Inc.
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Visual analysis of trash bin processing on garbage trucks in low resolution video
NASA Astrophysics Data System (ADS)
Sidla, Oliver; Loibner, Gernot
2015-03-01
We present a system for trash can detection and counting from a camera which is mounted on a garbage collection truck. A working prototype has been successfully implemented and tested with several hours of real-world video. The detection pipeline consists of HOG detectors for two trash can sizes, and meanshift tracking and low level image processing for the analysis of the garbage disposal process. Considering the harsh environment and unfavorable imaging conditions, the process works already good enough so that very useful measurements from video data can be extracted. The false positive/false negative rate of the full processing pipeline is about 5-6% at fully automatic operation. Video data of a full day (about 8 hrs) can be processed in about 30 minutes on a standard PC.
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Patel, Bhavika K; Naylor, Michelle E; Kosiorek, Heidi E; Lopez-Alvarez, Yania M; Miller, Adrian M; Pizzitola, Victor J; Pockaj, Barbara A
Supplement tomosynthesis-detected architectural distortions (AD) with CESM to better characterize malignant vs benign lesions. Retrospective review CESM prior to biopsied AD. Pathology: benign, radial scar, or malignant. 49 lesions (45 patients). 29 invasive cancers, 1 DCIS (range, 0.4-4.7cm); 9 radial scars; 10 benign. 37 (75.5%) ADs had associated enhancement. PPV 78.4% (29/37), sensitivity 96.7% (29/30); specificity, 57.9% (11/19); NPV, 91.7% (11/12). False-positive rate 21.6% (8/37); false-negative rate, 8.3% (1/12). Accuracy 81.6% (40/49). High sensitivity and NPV of CESM in patients with AD is promising as an adjunct tool in diagnosing malignancy and avoiding unnecessary biopsy, respectively. Copyright © 2017 Elsevier Inc. All rights reserved.
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NASA Astrophysics Data System (ADS)
Karfa, Paramita; Madhuri, Rashmi; Sharma, Prashant K.
2017-05-01
In this work, a sensitive and selective fluorescent molecularly imprinted polymer (MIP) was developed for detection of hepatocellular carcinoma (HCC) biomarker i.e. alpha feto protein (AFP) using Ag/AgCl as platform. Here, the carbon dots and Ag/AgCl nanoparticles were functionalized with vinyl groups and used as functional monomer for synthesis of AFP-imprinted polymer. The imprinted polymer shows a linear range of 3.96 ng mL-1 to 80.0 ng mL-1 with detection limit of 0.42 ng mL-1.The adsorption property of the MIP@Ag/AgCl was studied and shows the high affinity binding towards their target analyte without any cross-reactivity and false-positive or false-negative results.
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Do juries meet our expectations?
Arkes, Hal R; Mellers, Barbara A
2002-12-01
Surveys of public opinion indicate that people have high expectations for juries. When it comes to serious crimes, most people want errors of convicting the innocent (false positives) or acquitting the guilty (false negatives) to fall well below 10%. Using expected utility theory, Bayes' Theorem, signal detection theory, and empirical evidence from detection studies of medical decision making, eyewitness testimony, and weather forecasting, we argue that the frequency of mistakes probably far exceeds these "tolerable" levels. We are not arguing against the use of juries. Rather, we point out that a closer look at jury decisions reveals a serious gap between what we expect from juries and what probably occurs. When deciding issues of guilt and/or punishing convicted criminals, we as a society should recognize and acknowledge the abundance of error.
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Damaskos, Spyros; Griniatsos, John; Tsekouras, Nikolaos; Georgopoulos, Sotirios; Klonaris, Chris; Bastounis, Elias; Tsiklakis, Kostas
2008-11-01
To evaluate the reliability of panoramic radiograph (PR) for carotid artery atheroma detection, by comparing its results with the carotid-vertebral digital subtraction angiography (DSA) findings, as well as with the detected calcium deposition in the carotid plaques, which were surgically resected, using direct radiographs. Forty consecutive patients suffering from carotid artery atherosclerotic occlusive disease confirmed by preoperative DSA, fulfilling the criteria for carotid endarterectomy, were operated on. Preoperatively, all of the patients had undergone PR, while postoperatively all of the surgically resected carotid plaques were radiographed using radiographic films and submitted to histologic examination. Compared with the DSA and the radiographic film findings, the PR results were classified as: 1) true-positive; 2) true-negative; 3) false-positive; or 4) false-negative. Panoramic radiograph has low sensitivity and specificity compared with the DSA findings and the direct radiographs results. However, a positive predictive value (PPV) of 100% per patient as well as for luminal stenosis >80% was documented. Even in the subgroup of patients who fulfill the criteria for carotid endarterectomy, PR has a low sensitivity and specificity; therefore, it cannot be considered to be a useful screening tool for atheroma detection in the general dental population. However, the 100% PPV per patient and for luminal stenosis >80%, indicates that positive calcification PR findings at the C(3)-C(4) region are highly suggestive for carotid artery atherosclerotic occlusive disease. Therefore, especially asymptomatic patients should be referred for further examination.
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Terterov, Dimitry; Leung, Philemon Ho-Yan; Twells, Laurie K.; Gregory, Deborah M.; Smith, Chris; Boone, Darrell; Pace, David
2017-01-01
Background Although laparoscopic sleeve gastrectomy (LSG) has been shown to be a safe and effective treatment for severe obesity (body mass index ≥ 35), staple line leaks remain a major complication and account for a substantial portion of the procedure’s morbidity and mortality. Many centres performing LSG routinely obtain contrast studies on postoperative day 1 for early detection of staple line leaks. We examined the usefulness of Gastrografin swallow as an early detection test for staple line leaks on postoperative day 1 after LSG as well as the associated costs. Methods We conducted a retrospective review of a prospectively collected database that included 200 patients who underwent LSG for severe obesity between 2011 and 2014. Primary outcome measures were the incidence of staple line leaks and the results of Gastrografin swallow tests. We obtained imaging costs from appropriate hospital departments. Results Gastrografin swallow was obtained on postoperative day 1 for all 200 patients who underwent LSG. Three patients (1.5%) were found to have staple line leaks. Gastrograffin swallows yielded 1 true positive result and 2 false negatives. The false negatives were subsequently diagnosed on computed tomography (CT) scan. The sensitivity of Gastrografin swallow in this study was 33%. For 200 patients, the total direct cost of the Gastrografin swallows was $35 000. Conclusion The use of routine upper gastrointestinal contrast studies for early detection of staple line leaks has low sensitivity and is costly. We recommend selective use of CT instead. PMID:28742012
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Terterov, Dimitry; Leung, Philemon Ho-Yan; Twells, Laurie K; Gregory, Deborah M; Smith, Chris; Boone, Darrell; Pace, David
2017-09-01
Although laparoscopic sleeve gastrectomy (LSG) has been shown to be a safe and effective treatment for severe obesity (body mass index ≥ 35), staple line leaks remain a major complication and account for a substantial portion of the procedure's morbidity and mortality. Many centres performing LSG routinely obtain contrast studies on postoperative day 1 for early detection of staple line leaks. We examined the usefulness of Gastrografin swallow as an early detection test for staple line leaks on postoperative day 1 after LSG as well as the associated costs. We conducted a retrospective review of a prospectively collected database that included 200 patients who underwent LSG for severe obesity between 2011 and 2014. Primary outcome measures were the incidence of staple line leaks and the results of Gastrografin swallow tests. We obtained imaging costs from appropriate hospital departments. Gastrografin swallow was obtained on postoperative day 1 for all 200 patients who underwent LSG. Three patients (1.5%) were found to have staple line leaks. Gastrograffin swallows yielded 1 true positive result and 2 false negatives. The false negatives were subsequently diagnosed on computed tomography (CT) scan. The sensitivity of Gastrografin swallow in this study was 33%. For 200 patients, the total direct cost of the Gastrografin swallows was $35 000. The use of routine upper gastrointestinal contrast studies for early detection of staple line leaks has low sensitivity and is costly. We recommend selective use of CT instead.
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Huang, Ke; Huang, Lingyi; van Breemen, Richard B
2015-04-07
Metabolic activation of drugs to electrophilic species is responsible for over 60% of black box warnings and drug withdrawals from the market place in the United States. Reactive metabolite trapping using glutathione (GSH) and analysis using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) or HPLC with high resolution mass spectrometry (mass defect filtering) have enabled screening for metabolic activation to become routine during drug development. However, current MS-based approaches cannot detect all GSH conjugates present in complex mixtures, especially those present in extracts of botanical dietary supplements. To overcome these limitations, a fast triple quadrupole mass spectrometer-based approach was developed that can detect positively and negatively charged GSH conjugates in a single analysis without the need for advanced knowledge of the elemental compositions of potential conjugates and while avoiding false positives. This approach utilized UHPLC instead of HPLC to shorten separation time and enhance sensitivity, incorporated stable-isotope labeled GSH to avoid false positives, and used fast polarity switching electrospray MS/MS to detect GSH conjugates that form positive and/or negative ions. The general new method was then used to test the licorice dietary supplement Glycyrrhiza glabra, which was found to form multiple GSH conjugates upon metabolic activation. Among the GSH conjugates found in the licorice assay were conjugates with isoliquiritigenin and glabridin, which is an irreversible inhibitor of cytochrome P450 enzymes.
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An Improved Extended-Spectrum-β-Lactamase Detection Test Utilizing Aztreonam plus Clavulanate.
Thomson, Gina K; Ayaz, Maaz; Lutes, Kelli; Thomson, Kenneth S
2018-01-01
Clinical laboratories test for extended-spectrum β-lactamases (ESBLs) for epidemiological and infection control purposes and also for the potential of cephalosporins to cause therapeutic failures. Testing can be problematic, because the CLSI does not recommend the testing of all producers of ESBLs and also falsely negative results may occur with isolates that coproduce AmpC. Boronic acid-supplemented tests can enhance ESBL detection in AmpC producers. Because aztreonam inhibits AmpCs, a study was designed to compare ESBL detection by the CLSI disk test (CLSI), a boronic acid-supplemented CLSI disk test (CLSI plus BA), and an aztreonam plus clavulanate disk test (ATM plus CA). The study tested 100 well-characterized Enterobacteriaceae , Acinetobacter baumannii , and Pseudomonas aeruginosa isolates. Seventy produced TEM, SHV, or CTX-M ESBLs, with 15 coproducing an AmpC and 11 coproducing a metallo-β-lactamase. Thirty ESBL-negative isolates were also tested. Tests were inoculated by CLSI methodology and interpreted as positive if an inhibitor caused a zone diameter increase of ≥5 mm. The percentages of ESBL producers detected were as follows: ATM plus CA, 95.7%; CLSI plus BA, 88.6%; and CLSI, 78.6%. When AmpC was coproduced, the sensitivities of the tests were as follows: ATM plus CA, 100%; CLSI plus BA, 93.3%; and CLSI, 60%. ATM plus CA also detected an ESBL in 90.1% of isolates that coproduced a metallo-β-lactamase. Falsely positive tests occurred only with the CLSI and CLSI plus BA tests. Overall, the ATM plus CA test detected ESBLs more accurately than the CLSI and CLSI plus BA tests, especially with isolates coproducing an AmpC or metallo-β-lactamase. Copyright © 2017 American Society for Microbiology.
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Aiding the Detection of QRS Complex in ECG Signals by Detecting S Peaks Independently.
Sabherwal, Pooja; Singh, Latika; Agrawal, Monika
2018-03-30
In this paper, a novel algorithm for the accurate detection of QRS complex by combining the independent detection of R and S peaks, using fusion algorithm is proposed. R peak detection has been extensively studied and is being used to detect the QRS complex. Whereas, S peaks, which is also part of QRS complex can be independently detected to aid the detection of QRS complex. In this paper, we suggest a method to first estimate S peak from raw ECG signal and then use them to aid the detection of QRS complex. The amplitude of S peak in ECG signal is relatively weak than corresponding R peak, which is traditionally used for the detection of QRS complex, therefore, an appropriate digital filter is designed to enhance the S peaks. These enhanced S peaks are then detected by adaptive thresholding. The algorithm is validated on all the signals of MIT-BIH arrhythmia database and noise stress database taken from physionet.org. The algorithm performs reasonably well even for the signals highly corrupted by noise. The algorithm performance is confirmed by sensitivity and positive predictivity of 99.99% and the detection accuracy of 99.98% for QRS complex detection. The number of false positives and false negatives resulted while analysis has been drastically reduced to 80 and 42 against the 98 and 84 the best results reported so far.
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Fox, Stefan; Strasdeit, Henry
2017-01-01
The "Rare Earth" hypothesis-put forward by Ward and Brownlee in their 2000 book of the same title-states that prokaryote-type organisms may be common in the universe but animals and higher plants are exceedingly rare. If this idea is correct, the search for extraterrestrial life is essentially the search for microorganisms. Various indicators may be used to detect extant or extinct microbial life beyond Earth. Among them are chemical biosignatures, such as biomolecules and stable isotope ratios. The present minireview focuses on the major problems associated with the identification of chemical biosignatures. Two main types of misinterpretation are distinguished, namely false positive and false negative results. The former can be caused by terrestrial biogenic contaminants or by abiotic products. Terrestrial contamination is a common problem in space missions that search for biosignatures on other planets and moons. Abiotic organics can lead to false positive results if erroneously interpreted as biomolecules, but also to false negatives, for example when an abiotic source obscures a less productive biological one. In principle, all types of putative chemical biosignatures are prone to misinterpretation. Some, however, are more reliable ("stronger") than others. These include: (i) homochiral polymers of defined length and sequence, comparable to proteins and polynucleotides; (ii) enantiopure compounds; (iii) the existence of only a subset of molecules when abiotic syntheses would produce a continuous range of molecules; the proteinogenic amino acids constitute such a subset. These considerations are particularly important for life detection missions to solar system bodies such as Mars, Europa, and Enceladus.
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Hadker, Nandini; Garg, Suchita; Costanzo, Cory; van der Helm, Wim; Creeden, James
2013-05-01
To quantify the financial impact of adding a novel serum test to the current diagnostic toolkit for preeclampsia (PE) detection in Germany. A decision-analytic model was created to quantify the economic impact of adding a recently developed novel diagnostic test for PE (Roche Diagnostics, Rotkreuz, Switzerland) to current diagnostic practice in Germany. The model simulated a cohort of 1000 pregnant patients receiving obstetric care and quantified the budget impact of adding the novel test to current German PE detection and management practices. The model estimates that the costs associated with managing a typical pregnancy in Germany are €941 when the novel test is used versus €1579 with standard practice. This represents savings of €637 per pregnant woman, even when the test is used as a supplementary diagnostic tool. The savings are attributed to the novel test's ability to better classify patients relative to current practice, specifically, its ability to reduce false negatives by 67% and false positives by 71%. The novel PE test has the potential to provide substantial cost savings to German healthcare payers, even when used as an addition to standard practice. Better classification of patients at risk for developing PE and declassification of those that are not compared to current practice leads to economic savings for the healthcare system. Furthermore, by reducing the rates of false-positive and false-negative classification relative to current standard of care, the test helps better target healthcare spending and lowers overall costs associated with PE care.
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Cost-effectiveness of WHO-Recommended Algorithms for TB Case Finding at Ethiopian HIV Clinics.
Adelman, Max W; McFarland, Deborah A; Tsegaye, Mulugeta; Aseffa, Abraham; Kempker, Russell R; Blumberg, Henry M
2018-01-01
The World Health Organization (WHO) recommends active tuberculosis (TB) case finding and a rapid molecular diagnostic test (Xpert MTB/RIF) to detect TB among people living with HIV (PLHIV) in high-burden settings. Information on the cost-effectiveness of these recommended strategies is crucial for their implementation. We conducted a model-based cost-effectiveness analysis comparing 2 algorithms for TB screening and diagnosis at Ethiopian HIV clinics: (1) WHO-recommended symptom screen combined with Xpert for PLHIV with a positive symptom screen and (2) current recommended practice algorithm (CRPA; based on symptom screening, smear microscopy, and clinical TB diagnosis). Our primary outcome was US$ per disability-adjusted life-year (DALY) averted. Secondary outcomes were additional true-positive diagnoses, and false-negative and false-positive diagnoses averted. Compared with CRPA, combining a WHO-recommended symptom screen with Xpert was highly cost-effective (incremental cost of $5 per DALY averted). Among a cohort of 15 000 PLHIV with a TB prevalence of 6% (900 TB cases), this algorithm detected 8 more true-positive cases than CRPA, and averted 2045 false-positive and 8 false-negative diagnoses compared with CRPA. The WHO-recommended algorithm was marginally costlier ($240 000) than CRPA ($239 000). In sensitivity analysis, the symptom screen/Xpert algorithm was dominated at low Xpert sensitivity (66%). In this model-based analysis, combining a WHO-recommended symptom screen with Xpert for TB diagnosis among PLHIV was highly cost-effective ($5 per DALY averted) and more sensitive than CRPA in a high-burden, resource-limited setting.
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Fox, Stefan; Strasdeit, Henry
2017-01-01
The “Rare Earth” hypothesis—put forward by Ward and Brownlee in their 2000 book of the same title—states that prokaryote-type organisms may be common in the universe but animals and higher plants are exceedingly rare. If this idea is correct, the search for extraterrestrial life is essentially the search for microorganisms. Various indicators may be used to detect extant or extinct microbial life beyond Earth. Among them are chemical biosignatures, such as biomolecules and stable isotope ratios. The present minireview focuses on the major problems associated with the identification of chemical biosignatures. Two main types of misinterpretation are distinguished, namely false positive and false negative results. The former can be caused by terrestrial biogenic contaminants or by abiotic products. Terrestrial contamination is a common problem in space missions that search for biosignatures on other planets and moons. Abiotic organics can lead to false positive results if erroneously interpreted as biomolecules, but also to false negatives, for example when an abiotic source obscures a less productive biological one. In principle, all types of putative chemical biosignatures are prone to misinterpretation. Some, however, are more reliable (“stronger”) than others. These include: (i) homochiral polymers of defined length and sequence, comparable to proteins and polynucleotides; (ii) enantiopure compounds; (iii) the existence of only a subset of molecules when abiotic syntheses would produce a continuous range of molecules; the proteinogenic amino acids constitute such a subset. These considerations are particularly important for life detection missions to solar system bodies such as Mars, Europa, and Enceladus. PMID:28970819
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Ramirez-Arcos, Sandra; DiFranco, Caesar; McIntyre, Terri; Goldman, Mindy
2017-09-01
Canadian Blood Services screens 100% of platelet concentrates (PCs) for bacterial contamination with the BacT/ALERT system. Quality-control sterility testing of 1% (≥10 units) of outdated PCs is performed monthly. Data from routine screening, quality-control testing, and septic reactions obtained from 2010 to 2016 are presented herein. In total, 601,988 buffy coat PC pools and 186,737 apheresis PCs were routinely screened with aerobic cultures over 6 years. Outdate quality-control testing of 8535 buffy coat and 8498 apheresis PCs was performed using aerobic and anaerobic cultures during the same period. Results were classified as "true-positives" when the same bacterium was isolated in initial and confirmatory cultures or "false-negatives" when bacteria were missed in early screening and were captured during quality-control sterility testing or through investigation of sepsis cases. During routine screening, the true-positive rates between buffy coat (0.94 per 10,000) and apheresis (0.96 per 10,000) PCs were similar (p = 0.9473). Seventy-five bacteria isolated during PC screening included Gram-positive and Gram-negative organisms. Six false-negative septic reactions were reported that implicated coagulase-negative staphylococci (n = 3) and Staphylococcus aureus (n = 3) for approximate rates of 1 per 100,000 transfusion reactions and 1 per 500,000 fatalities. During quality-control testing, the false-negative rates between buffy coat (8 per 10,000) and apheresis (9 per 10,000) PCs were similar (p = 0.7897). All 15 quality-control isolates were Gram-positive bacteria. The current bacterial screening protocol is efficacious for identifying Gram-negative bacteria. However, the high proportion of Gram-positive organisms detected on outdate quality-control testing and septic transfusion events demonstrates a residual safety risk that merits further intervention. © 2017 AABB.
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Mundangepfupfu, Tichaendepi; Waseem, Muhammad
2014-03-01
Hydatidiform mole (molar pregnancy) is a benign tumor of placental trophoblastic cells, which release human chorionic gonadotropin (hCG). Several case reports have described complete hydatidiform moles with false-negative urine qualitative hCG tests. These negative pregnancy tests have been attributed to the hook effect. We report an unusual presentation of a partial mole and review an alternative explanation for the negative hCG test. As partial moles are usually not associated with a large proliferation of trophoblastic cells, levels of hCG are commonly < 100,000 mIU/mL. The most common presentation of a hydatidiform mole is vaginal bleeding. Hydatidiform mole is associated with a risk of malignant transformation and disseminated disease. In a pregnant patient, vaginal bleeding and abdominal pain are common presentations. Molar pregnancy is an uncommon cause of abdominal pain and vaginal bleeding that should be considered. A 47-year-old female presented to the emergency department with abdominal pain and vaginal bleeding. Urine qualitative hCG was negative and serum quantitative hCG was 1,094,950 mIU/mL. Pelvic ultrasonography showed a uterine cavity containing a soft-tissue mass with multiple cystic lesions and the hydatidiform mole was extracted with suction curettage. Tissue pathology confirmed partial hydatidiform mole. In addition to the hook effect, we present another possible explanation for the false-negative test; namely the inability of some assays to detect hCG-degradation products, which may be higher in clinical samples from patients with hydatidiform mole. This case underscores the importance of knowing the limitations of the commonly used hCG assays. Copyright © 2014 Elsevier Inc. All rights reserved.
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[Computed tomography with computer-assisted detection of pulmonary nodules in dogs and cats].
Niesterok, C; Piesnack, S; Köhler, C; Ludewig, E; Alef, M; Kiefer, I
2015-01-01
The aim of this study was to assess the potential benefit of computer-assisted detection (CAD) of pulmonary nodules in veterinary medicine. Therefore, the CAD rate was compared to the detection rates of two individual examiners in terms of its sensitivity and false-positive findings. We included 51 dogs and 16 cats with pulmonary nodules previously diagnosed by computed tomography. First, the number of nodules ≥ 3 mm was recorded for each patient by two independent examiners. Subsequently, each examiner used the CAD software for automated nodule detection. With the knowledge of the CAD results, a final consensus decision on the number of nodules was achieved. The software used was a commercially available CAD program. The sensitivity of examiner 1 was 89.2%, while that of examiner 2 reached 87.4%. CAD had a sensitivity of 69.4%. With CAD, the sensitivity of examiner 1 increased to 94.7% and that of examiner 2 to 90.8%. The CAD-system, which we used in our study, had a moderate sensitivity of 69.4%. Despite its severe limitations, with a high level of false-positive and false-negative results, CAD increased the examiners' sensitivity. Therefore, its supportive role in diagnostics appears to be evident.
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Huo, Yuankai; Xu, Zhoubing; Bao, Shunxing; Bermudez, Camilo; Plassard, Andrew J.; Liu, Jiaqi; Yao, Yuang; Assad, Albert; Abramson, Richard G.; Landman, Bennett A.
2018-01-01
Spleen volume estimation using automated image segmentation technique may be used to detect splenomegaly (abnormally enlarged spleen) on Magnetic Resonance Imaging (MRI) scans. In recent years, Deep Convolutional Neural Networks (DCNN) segmentation methods have demonstrated advantages for abdominal organ segmentation. However, variations in both size and shape of the spleen on MRI images may result in large false positive and false negative labeling when deploying DCNN based methods. In this paper, we propose the Splenomegaly Segmentation Network (SSNet) to address spatial variations when segmenting extraordinarily large spleens. SSNet was designed based on the framework of image-to-image conditional generative adversarial networks (cGAN). Specifically, the Global Convolutional Network (GCN) was used as the generator to reduce false negatives, while the Markovian discriminator (PatchGAN) was used to alleviate false positives. A cohort of clinically acquired 3D MRI scans (both T1 weighted and T2 weighted) from patients with splenomegaly were used to train and test the networks. The experimental results demonstrated that a mean Dice coefficient of 0.9260 and a median Dice coefficient of 0.9262 using SSNet on independently tested MRI volumes of patients with splenomegaly.
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Contour-Based Corner Detection and Classification by Using Mean Projection Transform
Kahaki, Seyed Mostafa Mousavi; Nordin, Md Jan; Ashtari, Amir Hossein
2014-01-01
Image corner detection is a fundamental task in computer vision. Many applications require reliable detectors to accurately detect corner points, commonly achieved by using image contour information. The curvature definition is sensitive to local variation and edge aliasing, and available smoothing methods are not sufficient to address these problems properly. Hence, we propose Mean Projection Transform (MPT) as a corner classifier and parabolic fit approximation to form a robust detector. The first step is to extract corner candidates using MPT based on the integral properties of the local contours in both the horizontal and vertical directions. Then, an approximation of the parabolic fit is calculated to localize the candidate corner points. The proposed method presents fewer false-positive (FP) and false-negative (FN) points compared with recent standard corner detection techniques, especially in comparison with curvature scale space (CSS) methods. Moreover, a new evaluation metric, called accuracy of repeatability (AR), is introduced. AR combines repeatability and the localization error (Le) for finding the probability of correct detection in the target image. The output results exhibit better repeatability, localization, and AR for the detected points compared with the criteria in original and transformed images. PMID:24590354
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Contour-based corner detection and classification by using mean projection transform.
Kahaki, Seyed Mostafa Mousavi; Nordin, Md Jan; Ashtari, Amir Hossein
2014-02-28
Image corner detection is a fundamental task in computer vision. Many applications require reliable detectors to accurately detect corner points, commonly achieved by using image contour information. The curvature definition is sensitive to local variation and edge aliasing, and available smoothing methods are not sufficient to address these problems properly. Hence, we propose Mean Projection Transform (MPT) as a corner classifier and parabolic fit approximation to form a robust detector. The first step is to extract corner candidates using MPT based on the integral properties of the local contours in both the horizontal and vertical directions. Then, an approximation of the parabolic fit is calculated to localize the candidate corner points. The proposed method presents fewer false-positive (FP) and false-negative (FN) points compared with recent standard corner detection techniques, especially in comparison with curvature scale space (CSS) methods. Moreover, a new evaluation metric, called accuracy of repeatability (AR), is introduced. AR combines repeatability and the localization error (Le) for finding the probability of correct detection in the target image. The output results exhibit better repeatability, localization, and AR for the detected points compared with the criteria in original and transformed images.
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Residual Agar Determination in Bacterial Spores by Electrospray Ionization Mass Spectrometry
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wahl, Karen L.; Colburn, Heather A.; Wunschel, David S.
2010-02-15
Presented here is an analytical method to detect residual agar from a bacterial spore sample as an indication of culturing on an agar plate. This method is based on the resolubilization of agar polysaccharide from a bacterial spore sample, enzymatic digestion, followed by electrospray ionization tandem mass spectrometry (ESI-MSn) analysis for detection of a specific agar fragment ion. A range of Bacillus species and strains were selected to demonstrate the effectiveness of this approach. The characteristic agar fragment ion was detected in the spores grown on agar that were washed from 1 to 5 times, irradiated or non-irradiated and notmore » in the spores grown in broth. A sample containing approximately 108 spores is currently needed for confident detection of residual agar from culture on agar plates in the presence of bacterial spores with a limit of detection of approximately 1 ppm agar spiked into a broth-grown spore sample. The results of a proficiency test with 42 blinded samples are presented demonstrating the utility of this method with no false positives and only 3 false negatives for samples that were below the detection level of the method as documented.« less
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INFRARED- BASED BLINK DETECTING GLASSES FOR FACIAL PACING: TOWARDS A BIONIC BLINK
Frigerio, Alice; Hadlock, Tessa A; Murray, Elizabeth H; Heaton, James T
2015-01-01
IMPORTANCE Facial paralysis remains one of the most challenging conditions to effectively manage, often causing life-altering deficits in both function and appearance. Facial rehabilitation via pacing and robotic technology has great yet unmet potential. A critical first step towards reanimating symmetrical facial movement in cases of unilateral paralysis is the detection of healthy movement to use as a trigger for stimulated movement. OBJECTIVE To test a blink detection system that can be attached to standard eyeglasses and used as part of a closed-loop facial pacing system. DESIGN Standard safety glasses were equipped with an infrared (IR) emitter/detector pair oriented horizontally across the palpebral fissure, creating a monitored IR beam that became interrupted when the eyelids closed. SETTING Tertiary care Facial Nerve Center. PARTICIPANTS 24 healthy volunteers. MAIN OUTCOME MEASURE Video-quantified blinking was compared with both IR sensor signal magnitude and rate of change in healthy participants with their gaze in repose, while they shifted gaze from central to far peripheral positions, and during the production of particular facial expressions. RESULTS Blink detection based on signal magnitude achieved 100% sensitivity in forward gaze, but generated false-detections on downward gaze. Calculations of peak rate of signal change (first derivative) typically distinguished blinks from gaze-related lid movements. During forward gaze, 87% of detected blink events were true positives, 11% were false positives, and 2% false negatives. Of the 11% false positives, 6% were associated with partial eyelid closures. During gaze changes, false blink detection occurred 6.3% of the time during lateral eye movements, 10.4% during upward movements, 46.5% during downward movements, and 5.6% for movements from an upward or downward gaze back to the primary gaze. Facial expressions disrupted sensor output if they caused substantial squinting or shifted the glasses. CONCLUSION AND RELEVANCE Our blink detection system provides a reliable, non-invasive indication of eyelid closure using an invisible light beam passing in front of the eye. Future versions will aim to mitigate detection errors by using multiple IR emitter/detector pairs mounted on the glasses, and alternative frame designs may reduce shifting of the sensors relative to the eye during facial movements. PMID:24699708
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Computer-aided marginal artery detection on computed tomographic colonography
NASA Astrophysics Data System (ADS)
Wei, Zhuoshi; Yao, Jianhua; Wang, Shijun; Liu, Jiamin; Summers, Ronald M.
2012-03-01
Computed tomographic colonography (CTC) is a minimally invasive technique for colonic polyps and cancer screening. The marginal artery of the colon, also known as the marginal artery of Drummond, is the blood vessel that connects the inferior mesenteric artery with the superior mesenteric artery. The marginal artery runs parallel to the colon for its entire length, providing the blood supply to the colon. Detecting the marginal artery may benefit computer-aided detection (CAD) of colonic polyp. It can be used to identify teniae coli based on their anatomic spatial relationship. It can also serve as an alternative marker for colon localization, in case of colon collapse and inability to directly compute the endoluminal centerline. This paper proposes an automatic method for marginal artery detection on CTC. To the best of our knowledge, this is the first work presented for this purpose. Our method includes two stages. The first stage extracts the blood vessels in the abdominal region. The eigenvalue of Hessian matrix is used to detect line-like structures in the images. The second stage is to reduce the false positives in the first step. We used two different masks to exclude the false positive vessel regions. One is a dilated colon mask which is obtained by colon segmentation. The other is an eroded visceral fat mask which is obtained by fat segmentation in the abdominal region. We tested our method on a CTC dataset with 6 cases. Using ratio-of-overlap with manual labeling of the marginal artery as the standard-of-reference, our method yielded true positive, false positive and false negative fractions of 89%, 33%, 11%, respectively.
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Sensitivity and Specificity of Histoplasma Antigen Detection by Enzyme Immunoassay.
Cunningham, Lauren; Cook, Audrey; Hanzlicek, Andrew; Harkin, Kenneth; Wheat, Joseph; Goad, Carla; Kirsch, Emily
2015-01-01
The objective of this study was to evaluate the sensitivity and specificity of an antigen enzyme immunoassay (EIA) on urine samples for the diagnosis of histoplasmosis in dogs. This retrospective medical records review included canine cases with urine samples submitted for Histoplasma EIA antigen assay between 2007 and 2011 from three veterinary institutions. Cases for which urine samples were submitted for Histoplasma antigen testing were reviewed and compared to the gold standard of finding Histoplasma organisms or an alternative diagnosis on cytology or histopathology. Sensitivity, specificity, negative predictive value, positive predictive value, and the kappa coefficient and associated confidence interval were calculated for the EIA-based Histoplasma antigen assay. Sixty cases met the inclusion criteria. Seventeen cases were considered true positives based on identification of the organism, and 41 cases were considered true negatives with an alternative definitive diagnosis. Two cases were considered false negatives, and there were no false positives. Sensitivity was 89.47% and the negative predictive value was 95.35%. Specificity and the positive predictive value were both 100%. The kappa coefficient was 0.9207 (95% confidence interval, 0.8131-1). The Histoplasma antigen EIA test demonstrated high specificity and sensitivity for the diagnosis of histoplasmosis in dogs.
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McMahon, Tanis C.; Blais, Burton W.; Wong, Alex; Carrillo, Catherine D.
2017-01-01
Foodborne illness attributed to enterohemorrhagic E. coli (EHEC), a highly pathogenic subset of Shiga toxin-producing E. coli (STEC), is increasingly recognized as a significant public health issue. Current microbiological methods for identification of EHEC in foods often use PCR-based approaches to screen enrichment broth cultures for characteristic gene markers [i.e., Shiga toxin (stx) and intimin (eae)]. However, false positives arise when complex food matrices, such as beef, contain mixtures of eae-negative STEC and eae-positive E. coli, but no EHEC with both markers in a single cell. To reduce false-positive detection of EHEC in food enrichment samples, a Multiplexed, Single Intact Cell droplet digital PCR (MuSIC ddPCR) assay capable of detecting the co-occurrence of the stx and eae genes in a single bacterial cell was developed. This method requires: (1) dispersal of intact bacteria into droplets; (2) release of genomic DNA (gDNA) by heat lysis; and (3) amplification and detection of genetic targets (stx and eae) using standard TaqMan chemistries with ddPCR. Performance of the method was tested with panels of EHEC and non-target E. coli. By determining the linkage (i.e., the proportion of droplets in which stx and eae targets were both amplified), samples containing EHEC (typically greater than 20% linkage) could be distinguished from samples containing mixtures of eae-negative STEC and eae-positive E. coli (0–2% linkage). The use of intact cells was necessary as this linkage was not observed with gDNA extracts. EHEC could be accurately identified in enrichment broth cultures containing excess amounts of background E. coli and in enrichment cultures derived from ground beef/pork and leafy-green produce samples. To our knowledge, this is the first report of dual-target detection in single bacterial cells using ddPCR. The application of MuSIC ddPCR to enrichment-culture screening would reduce false-positives, thereby improving the cost, speed, and accuracy of current methods for EHEC detection in foods. PMID:28303131
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McMahon, Tanis C; Blais, Burton W; Wong, Alex; Carrillo, Catherine D
2017-01-01
Foodborne illness attributed to enterohemorrhagic E. coli (EHEC), a highly pathogenic subset of Shiga toxin-producing E. coli (STEC), is increasingly recognized as a significant public health issue. Current microbiological methods for identification of EHEC in foods often use PCR-based approaches to screen enrichment broth cultures for characteristic gene markers [i.e., Shiga toxin ( stx ) and intimin ( eae )]. However, false positives arise when complex food matrices, such as beef, contain mixtures of eae -negative STEC and eae -positive E. coli , but no EHEC with both markers in a single cell. To reduce false-positive detection of EHEC in food enrichment samples, a Multiplexed, Single Intact Cell droplet digital PCR (MuSIC ddPCR) assay capable of detecting the co-occurrence of the stx and eae genes in a single bacterial cell was developed. This method requires: (1) dispersal of intact bacteria into droplets; (2) release of genomic DNA (gDNA) by heat lysis; and (3) amplification and detection of genetic targets ( stx and eae ) using standard TaqMan chemistries with ddPCR. Performance of the method was tested with panels of EHEC and non-target E. coli . By determining the linkage (i.e., the proportion of droplets in which stx and eae targets were both amplified), samples containing EHEC (typically greater than 20% linkage) could be distinguished from samples containing mixtures of eae -negative STEC and eae -positive E. coli (0-2% linkage). The use of intact cells was necessary as this linkage was not observed with gDNA extracts. EHEC could be accurately identified in enrichment broth cultures containing excess amounts of background E. coli and in enrichment cultures derived from ground beef/pork and leafy-green produce samples. To our knowledge, this is the first report of dual-target detection in single bacterial cells using ddPCR. The application of MuSIC ddPCR to enrichment-culture screening would reduce false-positives, thereby improving the cost, speed, and accuracy of current methods for EHEC detection in foods.
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Cragg, Jenna L.; Burger, Alan E.; Piatt, John F.
2015-01-01
Cryptic nest sites and secretive breeding behavior make population estimates and monitoring of Marbled Murrelets Brachyramphus marmoratus difficult and expensive. Standard audio-visual and radar protocols have been refined but require intensive field time by trained personnel. We examined the detection range of automated sound recorders (Song Meters; Wildlife Acoustics Inc.) and the reliability of automated recognition models (“recognizers”) for identifying and quantifying Marbled Murrelet vocalizations during the 2011 and 2012 breeding seasons at Kodiak Island, Alaska. The detection range of murrelet calls by Song Meters was estimated to be 60 m. Recognizers detected 20 632 murrelet calls (keer and keheer) from a sample of 268 h of recordings, yielding 5 870 call series, which compared favorably with human scanning of spectrograms (on average detecting 95% of the number of call series identified by a human observer, but not necessarily the same call series). The false-negative rate (percentage of murrelet call series that the recognizers failed to detect) was 32%, mainly involving weak calls and short call series. False-positives (other sounds included by recognizers as murrelet calls) were primarily due to complex songs of other bird species, wind and rain. False-positives were lower in forest nesting habitat (48%) and highest in shrubby vegetation where calls of other birds were common (97%–99%). Acoustic recorders tracked spatial and seasonal trends in vocal activity, with higher call detections in high-quality forested habitat and during late July/early August. Automated acoustic monitoring of Marbled Murrelet calls could provide cost-effective, valuable information for assessing habitat use and temporal and spatial trends in nesting activity; reliability is dependent on careful placement of sensors to minimize false-positives and on prudent application of digital recognizers with visual checking of spectrograms.
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Seto, Yasuo; Sekiguchi, Hiroshi; Maruko, Hisashi; Yamashiro, Shigeharu; Sano, Yasuhiro; Takayama, Yasuo; Sekioka, Ryoji; Yamaguchi, Shintaro; Kishi, Shintaro; Satoh, Takafumi; Sekiguchi, Hiroyuki; Iura, Kazumitsu; Nagashima, Hisayuki; Nagoya, Tomoki; Tsuge, Kouichiro; Ohsawa, Isaac; Okumura, Akihiko; Takada, Yasuaki; Ezawa, Naoya; Watanabe, Susumu; Hashimoto, Hiroaki
2014-05-06
A highly sensitive and specific real-time field-deployable detection technology, based on counterflow air introduction atmospheric pressure chemical ionization, has been developed for a wide range of chemical warfare agents (CWAs) comprising gaseous (two blood agents, three choking agents), volatile (six nerve gases and one precursor agent, five blister agents), and nonvolatile (three lachrymators, three vomiting agents) agents in air. The approach can afford effective chemical ionization, in both positive and negative ion modes, for ion trap multiple-stage mass spectrometry (MS(n)). The volatile and nonvolatile CWAs tested provided characteristic ions, which were fragmented into MS(3) product ions in positive and negative ion modes. Portions of the fragment ions were assigned by laboratory hybrid mass spectrometry (MS) composed of linear ion trap and high-resolution mass spectrometers. Gaseous agents were detected by MS or MS(2) in negative ion mode. The limits of detection for a 1 s measurement were typically at or below the microgram per cubic meter level except for chloropicrin (submilligram per cubic meter). Matrix effects by gasoline vapor resulted in minimal false-positive signals for all the CWAs and some signal suppression in the case of mustard gas. The moisture level did influence the measurement of the CWAs.
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Iacocca, Michael A; Wang, Jian; Dron, Jacqueline S; Robinson, John F; McIntyre, Adam D; Cao, Henian; Hegele, Robert A
2017-11-01
Familial hypercholesterolemia (FH) is a heritable condition of severely elevated LDL cholesterol, caused predominantly by autosomal codominant mutations in the LDL receptor gene ( LDLR ). In providing a molecular diagnosis for FH, the current procedure often includes targeted next-generation sequencing (NGS) panels for the detection of small-scale DNA variants, followed by multiplex ligation-dependent probe amplification (MLPA) in LDLR for the detection of whole-exon copy number variants (CNVs). The latter is essential because ∼10% of FH cases are attributed to CNVs in LDLR ; accounting for them decreases false negative findings. Here, we determined the potential of replacing MLPA with bioinformatic analysis applied to NGS data, which uses depth-of-coverage analysis as its principal method to identify whole-exon CNV events. In analysis of 388 FH patient samples, there was 100% concordance in LDLR CNV detection between these two methods: 38 reported CNVs identified by MLPA were also successfully detected by our NGS method, while 350 samples negative for CNVs by MLPA were also negative by NGS. This result suggests that MLPA can be removed from the routine diagnostic screening for FH, significantly reducing associated costs, resources, and analysis time, while promoting more widespread assessment of this important class of mutations across diagnostic laboratories. Copyright © 2017 by the American Society for Biochemistry and Molecular Biology, Inc.
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The use of a differential fluorescent staining method to detect bacteriuria.
Ciancaglini, Ettore; Fazii, Paolo; Sforza, Giuseppe Riario
2004-01-01
This report describes a differential staining method which distinguishes gram-positive from gram-negative bacteria in fluorescence. Gram-positive bacteria appear yellow and gram-negative bacteria appear green. The method is based on two fluorochromes, one acting in the wavelength of red, i.e. the acridine orange, and another acting in the wavelength of green, i.e. the fluorescein, which together form a red/ green system. In this report we compared the accuracy of the differential fluorescent staining method and the Gram stain in screening for bacteriuria, as detected by conventional cultures. A total of 1487 urine samples were tested. 289 cultures were positive. 237 specimens grew a single organism at 10(5) and 10(4) CFU/ml. 224 smears were detected by the differential fluorescent staining method and 162 were detected by Gram stain. 1198 samples failed to grow organisms at 10(5) and 10(4) CFU/ml. 107 smears were falsely positive by the fluorescent staining procedure and 289 were falsely positive by the Gram stain. On the basis of the culture results, the sensitivity of the differential fluorescent staining method was 94.5% and that of the Gram stain 68.3%. The specificity of the fluorescent staining procedure was 91.6% and that of the Gram stain 75.8%. The positive predictive value and the negative predictive value of the fluorescent staining method were 67.6% and 98.8%, respectively. Those of the Gram stain were 35.9% and 92.3%, respectively. A wide range of microbiological and chemical techniques are available to identify bacteria in urine. This fluorescent staining method represents a simple, rapid, reliable method with low-running costs. The main advantage of this technique is that it enables the microbiologist to exclude the presence of bacteria in the urine within a short time after specimen receipt and to eliminate a large number of specimens for culture with significant cost saving. Another advantage of the method is that it allows to distinguish gram-positive from gram-negative bacteria in positive slides on the same day the sample is obtained. The stained smears were easily interpreted, even when the bacterial counts in the specimen were low.
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Nation, Javan; Jiang, Wen
2017-01-01
To test the ability of a handheld metal detector (HHMD) to identify the presence and location of ingested metallic foreign bodies (MFBs) in children. Prospective case series enrolling children suspected of metallic foreign body ingestion presenting to the Emergency Department. Thirty-eight children were enrolled and the HHMD was used to detect the presence and location of a MFB. Results were compared to standard radiographic studies. Thirty-seven of the 38 ingested foreign bodies were MFBs. Of the 37 MFBs, the HHMD positively identified 33, and 4 were missed by HHMD but identified on radiography. When positive, the location indicated by HHMD correlated 100% with radiograph. There were 33 true positives, 0 false positives, 4 false negatives, and 1 true negative. This resulted in a sensitivity of 89% (95% CI of 75%-96%) and specificity of 100% (95% CI of 2.5%-100%). Our study demonstrates the accuracy of HHMD in the identification and localization of metallic foreign bodies. We propose an emergency room foreign body protocol that uses HHMD as an early screening tool in triage in order to expedite the process of obtaining Otolaryngology consultation and potentially shorten the wait time to the operating room or discharge. In instances were outside films are previously performed, HHMD use may be able to minimize the overall radiation exposure to children by obviating the need for repeat radiographs. As the sensitivity is not 100%, a negative HHMD screening does not negate the need for a standard radiograph in order to avoid missed MFBs. HHMD is best suited for detection of coins, which accounts for the majority of the MFB ingestions, and may not be suitable for all metallic objects since the amount of metal may decrease its sensitivity. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
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Bjornsdottir-Butler, Kristin; Jones, Jessica L; Benner, Ronald; Burkhardt, William
2011-05-01
Prompt detection of bacteria that contribute to scombrotoxin (histamine) fish poisoning can aid in the detection of potentially toxic fish products and prevent the occurrence of illness. We report development of the first real-time PCR method for rapid detection of Gram-negative histamine-producing bacteria (HPB) in fish. The real-time PCR assay was 100% inclusive for detecting high-histamine producing isolates and did not detect any of the low- or non-histamine producing isolates. The efficiency of the assay with/without internal amplification control ranged from 96-104% and in the presence of background flora and inhibitory matrices was 92/100% and 73-96%, respectively. This assay was used to detect HPB from naturally contaminated yellowfin tuna, bluefish, and false albacore samples. Photobacterium damselae (8), Plesiomonas shigelloides (2), Shewanella sp. (1), and Morganella morganii (1) were subsequently isolated from the real-time PCR positive fish samples. These results indicate that the real-time PCR assay developed in this study is a rapid and sensitive method for detecting high-HPB. The assay may be adapted for quantification of HPB, either directly or with an MPN-PCR method. Copyright © 2010. Published by Elsevier Ltd.
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Rice, Jason P; Seifert, Marva; Moser, Kathleen S; Rodwell, Timothy C
2017-01-01
Performance of the Xpert MTB/RIF assay, designed to simultaneously detect Mycobacterium tuberculosis complex (MTBC) and rifampin (RIF) resistance, has been well documented in low-resource settings with high TB-incidence. However, few studies have assessed its accuracy in low TB incidence settings. We evaluated the performance of Xpert MTB/RIF using clinical sputum specimens routinely collected from suspect pulmonary TB patients over a 4-year time period in San Diego County, California. Xpert MTB/RIF results were compared to acid-fast bacilli (AFB) smear microscopy, mycobacterial culture, and phenotypic drug susceptibility testing (DST). Of 751 sputum specimens, 134 (17.8%) were MTBC culture-positive and 2 (1.5%) were multidrug-resistant (MDR). For the detection of MTBC, Xpert MTB/RIF sensitivity was 89.6% (97.7% and 74.5% in smear-positive and -negative sputa, respectively) and specificity was 97.2%; while AFB smear sensitivity and specificity were 64.9% and 77.8%, respectively. Xpert MTB/RIF detected 35 of 47 smear-negative culture-positive specimens, and excluded 124 of 137 smear-positive culture-negative specimens. Xpert MTB/RIF also correctly excluded 99.2% (121/122) of nontuberculous mycobacteria (NTM) specimens, including all 33 NTM false-positives by smear microscopy. For the detection of RIF resistance, Xpert MTB/RIF sensitivity and specificity were 100% and 98.3%, respectively. Our findings demonstrate that Xpert MTB/RIF is able to accurately detect MTBC and RIF resistance in routinely collected respiratory specimens in a low TB-incidence setting, with comparable performance to that achieved in high-incidence settings; and suggest that under these conditions the assay has particular utility in detecting smear-negative TB cases, excluding smear-positive patients without MTBC disease, and differentiating MTBC from NTM.
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Rice, Jason P.; Moser, Kathleen S.; Rodwell, Timothy C.
2017-01-01
Performance of the Xpert MTB/RIF assay, designed to simultaneously detect Mycobacterium tuberculosis complex (MTBC) and rifampin (RIF) resistance, has been well documented in low-resource settings with high TB-incidence. However, few studies have assessed its accuracy in low TB incidence settings. We evaluated the performance of Xpert MTB/RIF using clinical sputum specimens routinely collected from suspect pulmonary TB patients over a 4-year time period in San Diego County, California. Xpert MTB/RIF results were compared to acid-fast bacilli (AFB) smear microscopy, mycobacterial culture, and phenotypic drug susceptibility testing (DST). Of 751 sputum specimens, 134 (17.8%) were MTBC culture-positive and 2 (1.5%) were multidrug-resistant (MDR). For the detection of MTBC, Xpert MTB/RIF sensitivity was 89.6% (97.7% and 74.5% in smear-positive and -negative sputa, respectively) and specificity was 97.2%; while AFB smear sensitivity and specificity were 64.9% and 77.8%, respectively. Xpert MTB/RIF detected 35 of 47 smear-negative culture-positive specimens, and excluded 124 of 137 smear-positive culture-negative specimens. Xpert MTB/RIF also correctly excluded 99.2% (121/122) of nontuberculous mycobacteria (NTM) specimens, including all 33 NTM false-positives by smear microscopy. For the detection of RIF resistance, Xpert MTB/RIF sensitivity and specificity were 100% and 98.3%, respectively. Our findings demonstrate that Xpert MTB/RIF is able to accurately detect MTBC and RIF resistance in routinely collected respiratory specimens in a low TB-incidence setting, with comparable performance to that achieved in high-incidence settings; and suggest that under these conditions the assay has particular utility in detecting smear-negative TB cases, excluding smear-positive patients without MTBC disease, and differentiating MTBC from NTM. PMID:29016684
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Discrepancy between culture and DNA probe analysis for the detection of periodontal bacteria.
van Steenbergen, T J; Timmerman, M F; Mikx, F H; de Quincey, G; van der Weijden, G A; van der Velden, U; de Graaff, J
1996-10-01
The purpose of this study was to compare a commercially available DNA probe technique with conventional cultural techniques for the detection of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia in subgingival plaque samples. Samples from 20 patients with moderate to severe periodontitis were evaluated at baseline and during a 15 months period of periodontal treatment. Paperpoints from 4 periodontal pockets per patient were forwarded to Omnigene for DNA probe analysis, and simultaneously inserted paperpoints from the same pockets were analyzed by standard culture techniques. In addition, mixed bacterial samples were constructed harbouring known proportions of 25 strains of A. actinomycetemcomitans, P. gingivalis and P. intermedia each. A relatively low concordance was found between both methods. At baseline a higher detection frequency was found for A. actinomycetemcomitans and P. gingivalis for the DNA probe technique; for P. intermedia the detection frequency by culture was higher. For A. actinomycetemcomitans, 21% of the culture positive samples was positive with the DNA probe. Testing the constructed bacterial samples with the DNA probe method resulted in about 16% false positive results for the 3 species tested. Furthermore, 40% of P. gingivalis strains were not detected by the DNA probe. The present data suggest that at least part of the discrepancies found between the DNA probe technique used and cultural methods are caused by false positive and false negative DNA probe results. Therefore, the value of this DNA probe method for the detection of periodontal pathogens is questionable.
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A Closer Look at Self-Reported Suicide Attempts: False Positives and False Negatives
ERIC Educational Resources Information Center
Ploderl, Martin; Kralovec, Karl; Yazdi, Kurosch; Fartacek, Reinhold
2011-01-01
The validity of self-reported suicide attempt information is undermined by false positives (e.g., incidences without intent to die), or by unreported suicide attempts, referred to as false negatives. In a sample of 1,385 Austrian adults, we explored the occurrence of false positives and false negatives with detailed, probing questions. Removing…
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Koita, Ousmane A; Doumbo, Ogobara K; Ouattara, Amed; Tall, Lalla K; Konaré, Aoua; Diakité, Mahamadou; Diallo, Mouctar; Sagara, Issaka; Masinde, Godfred L; Doumbo, Safiatou N; Dolo, Amagana; Tounkara, Anatole; Traoré, Issa; Krogstad, Donald J
2012-02-01
We identified 480 persons with positive thick smears for asexual Plasmodium falciparum parasites, of whom 454 had positive rapid diagnostic tests (RDTs) for the histidine-rich protein 2 (HRP2) product of the hrp2 gene and 26 had negative tests. Polymerase chain reaction (PCR) amplification for the histidine-rich repeat region of that gene was negative in one-half (10/22) of false-negative specimens available, consistent with spontaneous deletion. False-negative RDTs were found only in persons with asymptomatic infections, and multiplicities of infection (MOIs) were lower in persons with false-negative RDTs (both P < 0.001). These results show that parasites that fail to produce HRP2 can cause patent bloodstream infections and false-negative RDT results. The importance of these observations is likely to increase as malaria control improves, because lower MOIs are associated with false-negative RDTs and false-negative RDTs are more frequent in persons with asymptomatic infections. These findings suggest that the use of HRP2-based RDTs should be reconsidered.
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False negative rates in Drosophila cell-based RNAi screens: a case study
2011-01-01
Background High-throughput screening using RNAi is a powerful gene discovery method but is often complicated by false positive and false negative results. Whereas false positive results associated with RNAi reagents has been a matter of extensive study, the issue of false negatives has received less attention. Results We performed a meta-analysis of several genome-wide, cell-based Drosophila RNAi screens, together with a more focused RNAi screen, and conclude that the rate of false negative results is at least 8%. Further, we demonstrate how knowledge of the cell transcriptome can be used to resolve ambiguous results and how the number of false negative results can be reduced by using multiple, independently-tested RNAi reagents per gene. Conclusions RNAi reagents that target the same gene do not always yield consistent results due to false positives and weak or ineffective reagents. False positive results can be partially minimized by filtering with transcriptome data. RNAi libraries with multiple reagents per gene also reduce false positive and false negative outcomes when inconsistent results are disambiguated carefully. PMID:21251254
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Chen, X; Zhang, J; Feng, X; Chen, X; Yin, S; Wen, H; Zheng, S
2014-01-01
The patients with false immune diagnosis of hydatid disease were investigated for the humoural immune response to analyse the possible reasons and mechanism leading to false immune diagnosis. Two hundred and thirty-nine patients with nature-unknown cysts and 30 healthy controls were detected by immunological assays (four hydatid antigen-based immunogold filtration assay and enzyme-linked immune absorbent assay) and ultrasound. Sensitivity of and specificity of immunological assay and ultrasound were calculated, respectively. The serological diagnosis was compared with surgical pathology to screen the patients with false immune diagnosis for the immunoglobulin measurement and pathological analysis. The history and cyst characteristics were also reviewed. The results indicate the immunoglobulin has little influence on false immunodiagnosis. The false-negative immunodiagnosis was caused by the cysts' inactive status while the false positive caused by previous rupture, antigen cross-reaction. The clinical diagnosis of cystic echinococcosis requires a combination of immunodiagnosis and ultrasonography, which is the necessary complementary confirmation. PMID:24372157
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Breast 3 T-MR imaging: indication for stereotactic vacuum-assisted breast biopsy.
Yamamoto, Nobuko; Yoshizako, Takeshi; Yoshikawa, Kazuaki; Itakura, Masayuki; Maruyama, Riruke; Kitagaki, Hajime
2014-01-01
The purpose of this study was to assess indications for stereotactic vacuum-assisted breast biopsy (SVAB) evaluated by breast 3 T-magnetic resonance (3 T-MR) imaging in patients showing suspicious microcalcifications on mammography and negative ultrasound (US) findings. Fifty-five patients with 55 breast lesions showing suspicious microcalcifications on mammography and negative US findings underwent preoperative 3 T-MR examination including dynamic MR imaging. All patients underwent SVAB within 1 month of MR imaging. The pathological diagnosis of each breast lesion was made by examining tissues obtained by SVAB or radical/partial mastectomy. 3 T-MR imaging findings were evaluated by using the American College of Radiology Breast Imaging Reporting and Data System Atlas (BI-RADS-MRI) and then were correlated with the histopathological findings. When BI-RADS 4 and 5 MR imaging lesions were assumed to be malignant, the usefulness of 3 T-MR imaging was evaluated for diagnosis of impalpable breast lesions by SVAB among lesions with microcalcification detected by mammography and negative US findings. There were 21 malignant lesions, including 5 invasive ductal carcinomas, 16 lesions of ductal carcinoma in situ (DCIS). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 3 T-MR imaging for deciding the indications for SVAB was 90.5%, 97.1%, 95.0%, 94.3%, and 94.5%, respectively. The one-false negative case was a DCIS with small enhancing lesions (0.5 mm). The one false-positive case was ductal adenoma with a linear ductal pattern of enhancement. 3 T-MR imaging may be useful for deciding the indications for SVAB in patients who have breast lesions with microcalcification that are impalpable and are detected by mammography and negative US findings. However, our findings should be considered preliminary and further prospective investigation is required.
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A comparison of acoustic montoring methods for common anurans of the northeastern United States
Brauer, Corinne; Donovan, Therese; Mickey, Ruth M.; Katz, Jonathan; Mitchell, Brian R.
2016-01-01
Many anuran monitoring programs now include autonomous recording units (ARUs). These devices collect audio data for extended periods of time with little maintenance and at sites where traditional call surveys might be difficult. Additionally, computer software programs have grown increasingly accurate at automatically identifying the calls of species. However, increased automation may cause increased error. We collected 435 min of audio data with 2 types of ARUs at 10 wetland sites in Vermont and New York, USA, from 1 May to 1 July 2010. For each minute, we determined presence or absence of 4 anuran species (Hyla versicolor, Pseudacris crucifer, Anaxyrus americanus, and Lithobates clamitans) using 1) traditional human identification versus 2) computer-mediated identification with software package, Song Scope® (Wildlife Acoustics, Concord, MA). Detections were compared with a data set consisting of verified calls in order to quantify false positive, false negative, true positive, and true negative rates. Multinomial logistic regression analysis revealed a strong (P < 0.001) 3-way interaction between the ARU recorder type, identification method, and focal species, as well as a trend in the main effect of rain (P = 0.059). Overall, human surveyors had the lowest total error rate (<2%) compared with 18–31% total errors with automated methods. Total error rates varied by species, ranging from 4% for A. americanus to 26% for L. clamitans. The presence of rain may reduce false negative rates. For survey minutes where anurans were known to be calling, the odds of a false negative were increased when fewer individuals of the same species were calling.
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Padoan, R; Genoni, S; Moretti, E; Seia, M; Giunta, A; Corbetta, C
2002-01-01
A study was performed on the delayed diagnosis of cystic fibrosis (CF) in infants who had false-negative results in a neonatal screening programme. The genetic and clinical features of false-negative infants in this screening programme were assessed together with the efficiency of the screening procedure in the Lombardia region. In total, 774,687 newborns were screened using a two-step immunoreactive trypsinogen (IRT) (in the years 1990-1992), IRT/IRT + delF508 (1993-1998) or IRT/IRT + polymerase chain reaction (PCR) and oligonucleotide ligation assay (OLA) protocol (1998-1999). Out of 196 CF children born in the 10 y period 15 were false negative on screening (7.6%) and molecular analysis showed a high variability in the genotypes. The cystic fibrosis transmembrane regulator (CFTR) gene mutations identified were delF508, D1152H, R1066C, R334W, G542X, N1303K, F1052V, A120T, 3849 + 10kbC --> T, 2789 + 5G --> A, 5T-12TG and the novel mutation D110E. In three patients no mutation was identified after denaturing gradient gel electrophoresis of the majority of CFTR gene exons. The clinical phenotypes of CF children diagnosed by their symptoms at different ages were very mild. None of them presented with a severe lung disease. The majority of them did not seem to have been damaged by the delayed diagnosis. The combination of IRT assay plus genotype analysis (1998-1999) appears to be a more reliable method of detecting CF than IRT measurement alone or combined with only the delF508 mutation.
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Brownback, Kyle R; Pitts, Lucas R; Simpson, Steven Q
2013-09-01
Diagnosis of invasive pulmonary aspergillosis (IPA) is a challenging process in immunocompromised patients. Galactomannan (GM) antigen detection in bronchoalveolar lavage (BAL) fluid is a method to detect IPA with improved sensitivity over conventional studies. We sought to determine the diagnostic yield of BAL GM assay in a diverse population of immunocompromised patients. A retrospective review of 150 fiberoptic bronchoscopy (FOB) with BAL for newly diagnosed pulmonary infiltrate in immunocompromised patients was performed. Patient information, procedural details and laboratory studies were collected. BAL and serum samples were evaluated for GM using enzyme-linked immunoassay. Of 150 separate FOB with BAL, BAL GM was obtained in 143 samples. There were 31 positive BAL GM assays. In those 31 positive tests, 13 were confirmed as IPA, giving a positive predictive value of 41.9%. There was one false negative BAL GM. Of the 18 false positive BAL GM, 4 were receiving piperacillin-tazobactam and 11 were receiving an alternative beta-lactam antibiotic. BAL GM assay shows excellent sensitivity for diagnosing IPA. There was a significant number of false positive BAL GM assays and several of those patients were receiving beta-lactam antibiotics at the time of bronchoscopy. © 2013 Blackwell Verlag GmbH.
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Ianniello, Stefania; Di Giacomo, Vincenza; Sessa, Barbara; Miele, Vittorio
2014-09-01
Combined clinical examination and supine chest radiography have shown low accuracy in the assessment of pneumothorax in unstable patients with major chest trauma during the primary survey in the emergency room. The aim of our study was to evaluate the diagnostic accuracy of extended-focused assessment with sonography in trauma (e-FAST), in the diagnosis of pneumothorax, compared with the results of multidetector computed tomography (MDCT) and of invasive interventions (thoracostomy tube placement). This was a retrospective case series involving 368 consecutive unstable adult patients (273 men and 95 women; average age, 25 years; range, 16-68 years) admitted to our hospital's emergency department between January 2011 and December 2012 for major trauma (Injury Severity Score ≥ 15). We evaluated the accuracy of thoracic ultrasound in the detection of pneumothorax compared with the results of MDCT and invasive interventions (thoracostomy tube placement). Institutional review board approval was obtained prior to commencement of this study. Among the 736 lung fields included in the study, 87 pneumothoraces were detected with thoracic CT scans (23.6%). e-FAST detected 67/87 and missed 20 pneumothoraces (17 mild, 3 moderate). The diagnostic performance of ultrasound was: sensitivity 77% (74% in 2011 and 80% in 2012), specificity 99.8%, positive predictive value 98.5%, negative predictive value 97%, accuracy 97.2% (67 true positive; 668 true negative; 1 false positive; 20 false negative); 17 missed mild pneumothoraces were not immediately life-threatening (thickness less than 5 mm). Thoracic ultrasound (e-FAST) is a rapid and accurate first-line, bedside diagnostic modality for the diagnosis of pneumothorax in unstable patients with major chest trauma during the primary survey in the emergency room.
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[Evaluation of quality of HIV diagnostic procedures in Poland].
Parczewski, Miłosz; Madaliński, Kazimierz; Leszczyszyn-Pynka, Magdalena; Boroń-Kaczmarska, Anna
2010-01-01
The aim of this work was quality assessment of HIV diagnostic procedures in Poland, including human and technical resources as well as laboratory practice. Sixty questionnaires were distributed among diagnostic centers to obtain qualitative data. Basing on the survey data serological control using coded panels of HIV-1/2 samples was performed. Thirty-one filled questionnaires were received (50.8%). Surveyed laboratories perform from 350 to 5500 serological screening tests per year. In most of laboratories fourth generation assays are available, while Blood Donation Centers screen the blood both with serological assays and by HIV-RNA detection. Sanitary and Epidemiological Stations and academic laboratories hold the ISO/IEC 17025 or IS0 9001:2001 accreditation, five of the surveyed centers participate in Labquality assurance and two in Quality Control in Molecular Diagnostics programs. Data of control serological testing were received from 21 centers. In the quality control assessment 194 analyses were performed with 91 true negative, 2 false negative, 96 true positive and 5 false positive results. False negative rate of % and false positive rate of 5.2% was noted for this study. Currently, virtually no guidelines related to the HIV-diagnostics quality assurance and control in Poland are in delineated. Development of the national unified quality control system, basing on the central institution is highly desirable. National certification within the frames of the quality control and assurance program should be mandatory for all the diagnostic labs, and aim at improvement of reliability of the result distributed among clinicians and patients.
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He, Xianmin; Wei, Qing; Sun, Meiqian; Fu, Xuping; Fan, Sichang; Li, Yao
2006-05-01
Biological techniques such as Array-Comparative genomic hybridization (CGH), fluorescent in situ hybridization (FISH) and affymetrix single nucleotide pleomorphism (SNP) array have been used to detect cytogenetic aberrations. However, on genomic scale, these techniques are labor intensive and time consuming. Comparative genomic microarray analysis (CGMA) has been used to identify cytogenetic changes in hepatocellular carcinoma (HCC) using gene expression microarray data. However, CGMA algorithm can not give precise localization of aberrations, fails to identify small cytogenetic changes, and exhibits false negatives and positives. Locally un-weighted smoothing cytogenetic aberrations prediction (LS-CAP) based on local smoothing and binomial distribution can be expected to address these problems. LS-CAP algorithm was built and used on HCC microarray profiles. Eighteen cytogenetic abnormalities were identified, among them 5 were reported previously, and 12 were proven by CGH studies. LS-CAP effectively reduced the false negatives and positives, and precisely located small fragments with cytogenetic aberrations.
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Lai, Andrea Z; Schrock, Alexa B; Erlich, Rachel L; Ross, Jeffrey S; Miller, Vincent A; Yakirevich, Evgeny; Ali, Siraj M; Braiteh, Fadi
2017-07-01
ALK rearrangements have been observed in 0.05%-2.5% of patients with colorectal cancers (CRCs) and are predicted to be oncogenic drivers largely mutually exclusive of KRAS, NRAS, or BRAF alterations. Here we present the case of a patient with metastatic CRC who was treatment naïve at the time of molecular testing. Initial ALK immunohistochemistry (IHC) staining was negative, but parallel genomic profiling of both circulating tumor DNA (ctDNA) and tissue using similar hybrid capture-based assays each identified an identical STRN-ALK fusion. Subsequent ALK IHC staining of the same specimens was positive, suggesting that the initial result was a false negative. This report is the first instance of an ALK fusion in CRC detected using a ctDNA assay. Current guidelines for colorectal cancer (CRC) only recommend genomic assessment of KRAS, NRAS, BRAF, and microsatellite instability (MSI) status. ALK rearrangements are rare in CRC, but patients with activating ALK fusions have responded to targeted therapies ALK rearrangements can be detected by genomic profiling of ctDNA from blood or tissue, and this methodology may be informative in cases where immunohistochemistry (IHC) or other standard testing is negative. © AlphaMed Press 2017.
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ERIC Educational Resources Information Center
Greyson, Bruce
2005-01-01
Some persons who claim to have had near-death experiences (NDEs) fail research criteria for having had NDEs ("false positives"); others who deny having had NDEs do meet research criteria for having had NDEs ("false negatives"). The author evaluated false positive claims and false negative denials in an organization that promotes near-death…
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Siu, L Kristopher; Tsai, Yu-Kuo; Lin, Jung-Chung; Chen, Te-Li; Fung, Chang-Phone; Chang, Feng-Yee
2016-12-01
In this study, a novel colloidal gold-based immunochromatographic strip (ICS) containing anti-Klebsiella pneumoniae capsular polysaccharide polyclonal antibodies was developed to specifically detect K. pneumoniae serotypes K1 and K2. Capsular polysaccharide K1 and K2 antigens were first used to produce polyclonal anti-K1 and anti-K2 antibodies. Reference strains with different serotypes, nontypeable K. pneumoniae strains, and other bacterial species were then used to assess the sensitivity and specificity of these test strips. The detection limit was found to be 10 5 CFU, and the ICSs were stable for 6 months when stored at room temperature. No false-positive or false-negative results were observed, and equivalent results were obtained compared to those of more conventional test methods, such as PCR or serum agglutination. In conclusion, the ICS developed here requires no technical expertise and allows for the specific, rapid, and simultaneous detection of K. pneumoniae serotypes K1 and K2. Copyright © 2016, American Society for Microbiology. All Rights Reserved.
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Evaluation of BACTEC 9240 blood culture system by using high-volume aerobic resin media.
Schwabe, L D; Thomson, R B; Flint, K K; Koontz, F P
1995-01-01
The BACTEC 9240 blood culture system (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) is one of three automated, continuous-monitoring systems that is widely used in clinical laboratories. The BACTEC 9240 was compared with the BACTEC NR 660 for the detection of organisms and bacteremic episodes; time to detection of positive cultures; number of false-positive and false-negative cultures; and time needed to load, process, and perform quality control functions by using high-volume aerobic media. Blood specimens (5,282) were inoculated in equal volumes (5 to 10 ml per bottle) into BACTEC Plus Aerobic/F (9240 system) and BACTEC Plus NR26 (660 system) bottles. Clinically significant isolates were detected in 6.6% of cultures, representing 348 microorganisms and 216 bacteremic episodes. Two hundred forty-eight microorganisms were detected by both systems, 48 by the 9240 only and 52 by the 660 only (P = not significant). Of the bacteremic episodes, 158 were detected by both systems, 27 by the 9240 only and 31 by the 660 only (P = not significant). Analysis of data by month revealed equivalent recovery rates for both systems, with the exception of a 30-day period at one study site during which the 660 system detected significantly more microorganisms. Following a proprietary hardware design retrofit of the 9240 instrument, detection rates were again equivalent for the remaining three months at this study site. Positive cultures detected by both systems were detected an average of 4.3 h faster by the 9240 system (21 versus 25.3 h). The numbers of false-positive cultures for the 9240 and 660 systems were 40 (1.0%) and 9 ( < 1.0%), respectively.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7494044
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Limits of detection and decision. Part 3
NASA Astrophysics Data System (ADS)
Voigtman, E.
2008-02-01
It has been shown that the MARLAP (Multi-Agency Radiological Laboratory Analytical Protocols) for estimating the Currie detection limit, which is based on 'critical values of the non-centrality parameter of the non-central t distribution', is intrinsically biased, even if no calibration curve or regression is used. This completed the refutation of the method, begun in Part 2. With the field cleared of obstructions, the true theory underlying Currie's limits of decision, detection and quantification, as they apply in a simple linear chemical measurement system (CMS) having heteroscedastic, Gaussian measurement noise and using weighted least squares (WLS) processing, was then derived. Extensive Monte Carlo simulations were performed, on 900 million independent calibration curves, for linear, "hockey stick" and quadratic noise precision models (NPMs). With errorless NPM parameters, all the simulation results were found to be in excellent agreement with the derived theoretical expressions. Even with as much as 30% noise on all of the relevant NPM parameters, the worst absolute errors in rates of false positives and false negatives, was only 0.3%.
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Carvalho, Gustavo A; Minnett, Peter J; Fleming, Lora E; Banzon, Viva F; Baringer, Warner
2010-06-01
In a continuing effort to develop suitable methods for the surveillance of Harmful Algal Blooms (HABs) of Karenia brevis using satellite radiometers, a new multi-algorithm method was developed to explore whether improvements in the remote sensing detection of the Florida Red Tide was possible. A Hybrid Scheme was introduced that sequentially applies the optimized versions of two pre-existing satellite-based algorithms: an Empirical Approach (using water-leaving radiance as a function of chlorophyll concentration) and a Bio-optical Technique (using particulate backscatter along with chlorophyll concentration). The long-term evaluation of the new multi-algorithm method was performed using a multi-year MODIS dataset (2002 to 2006; during the boreal Summer-Fall periods - July to December) along the Central West Florida Shelf between 25.75°N and 28.25°N. Algorithm validation was done with in situ measurements of the abundances of K. brevis; cell counts ≥1.5×10(4) cells l(-1) defined a detectable HAB. Encouraging statistical results were derived when either or both algorithms correctly flagged known samples. The majority of the valid match-ups were correctly identified (~80% of both HABs and non-blooming conditions) and few false negatives or false positives were produced (~20% of each). Additionally, most of the HAB-positive identifications in the satellite data were indeed HAB samples (positive predictive value: ~70%) and those classified as HAB-negative were almost all non-bloom cases (negative predictive value: ~86%). These results demonstrate an excellent detection capability, on average ~10% more accurate than the individual algorithms used separately. Thus, the new Hybrid Scheme could become a powerful tool for environmental monitoring of K. brevis blooms, with valuable consequences including leading to the more rapid and efficient use of ships to make in situ measurements of HABs.
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Carvalho, Gustavo A.; Minnett, Peter J.; Fleming, Lora E.; Banzon, Viva F.; Baringer, Warner
2010-01-01
In a continuing effort to develop suitable methods for the surveillance of Harmful Algal Blooms (HABs) of Karenia brevis using satellite radiometers, a new multi-algorithm method was developed to explore whether improvements in the remote sensing detection of the Florida Red Tide was possible. A Hybrid Scheme was introduced that sequentially applies the optimized versions of two pre-existing satellite-based algorithms: an Empirical Approach (using water-leaving radiance as a function of chlorophyll concentration) and a Bio-optical Technique (using particulate backscatter along with chlorophyll concentration). The long-term evaluation of the new multi-algorithm method was performed using a multi-year MODIS dataset (2002 to 2006; during the boreal Summer-Fall periods – July to December) along the Central West Florida Shelf between 25.75°N and 28.25°N. Algorithm validation was done with in situ measurements of the abundances of K. brevis; cell counts ≥1.5×104 cells l−1 defined a detectable HAB. Encouraging statistical results were derived when either or both algorithms correctly flagged known samples. The majority of the valid match-ups were correctly identified (~80% of both HABs and non-blooming conditions) and few false negatives or false positives were produced (~20% of each). Additionally, most of the HAB-positive identifications in the satellite data were indeed HAB samples (positive predictive value: ~70%) and those classified as HAB-negative were almost all non-bloom cases (negative predictive value: ~86%). These results demonstrate an excellent detection capability, on average ~10% more accurate than the individual algorithms used separately. Thus, the new Hybrid Scheme could become a powerful tool for environmental monitoring of K. brevis blooms, with valuable consequences including leading to the more rapid and efficient use of ships to make in situ measurements of HABs. PMID:21037979
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Snyder, James W.; Munier, Gina K.; Johnson, Charles L.
2010-01-01
This study compared the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) real-time PCR assay to culture by the use of BBL CHROMagar MRSA for the detection of MRSA in 627 nasal surveillance specimens collected from intensive care unit (ICU) patients. The PCR assay had a sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 96.7%, 70.3%, and 100%, respectively. Nine of 19 false-positive PCR specimens grew methicillin-susceptible S. aureus (MSSA) from broth enrichment culture, of which two demonstrated evidence of mecA gene dropout. Compared to culture by the use of BBL CHROMagar MRSA, the BD GeneOhm MRSA PCR assay demonstrated sensitivity and specificity above 95% for the detection of MRSA nasal colonization and provided shorter turnaround time in generating positive and negative final results. PMID:20181916
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Bezold, G; Volkenandt, M; Gottlöber, P; Peter, R U
2000-12-01
PCR-based detection of microorganisms is widely used for diagnostic purposes. Most routine PCR applications do not control for inhibition of PCR, thus leading to false-negative results. One hundred eighteen swab samples obtained from skin and mucosa were investigated for the presence of herpes simplex virus (HSV), varicella-zoster virus (VZV), and the control gene betaglobin by internally controlled PCR with purified and unpurified DNA in parallel. With unpurified DNA, inhibition of PCR was detected in 23% of betaglobin PCRs, 25% of VZV PCRs, and 16% of HSV PCRs versus 3% each for purified DNA. Approximately 20% of the samples with positive results for HSV or VZV had negative or inhibited results using unpurified DNA. These results indicate that PCR from clinical swab specimens should be performed exclusively with internal controls because the positive control alone cannot exclude PCR inhibition in individual samples. Purification of DNA will decrease, but not exclude, PCR inhibition.
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Rácil, Z; Kocmanová, I; Wagnerová, B; Winterová, J; Lengerová, M; Moulis, M; Mayer, J
2008-01-01
PREMISES AND OBJECTIVES: Timely diagnosis is of critical importance for the prognosis of invasive aspergilosis (IA) patients. Over recent years, IA detection of galactomannan using the ELISA method has assumed growing importance. The objective of the study was to analyse the usability of the method in current clinical practice of a hemato-oncological ward. From May 2003 to October 2006, blood samples were taken from patients at IA risk to detect galactomannan (GM) in serum using the ELISA method. The patients who underwent the tests were classified by the probability of IA presence on the basis of the results of conventional diagnostic methods and section findings. A total of 11,360 serum samples from 911 adult patients were tested for GM presence. IA (probable/proven) was diagnosed in 42 (4.6%) of them. The rates of sensitivity, specificity, positive and negative predictive value of galactomannan detection for IA diagnosis in our ward were, respectively, 95.2%, 90.0%, 31.5% and 99.7%. The principal causes of the limited positive predictive value of the test were the high percentage of false-positive test results (mainly caused by concomitant administration of some penicillin antibiotics or Plasma-Lyte infusion solution), as well as the fact that a large percentage of patients we examined fell within the group of patients with hematological malignity with a very low prevalence of IA. GM detection in serum is associated with high sensitivity and excellent negative predictive value in IA diagnosis in hemato-oncological patients. Knowledge and elimination of possible causes of false-positive results as well as focusing the screening on patients at greatest risk of infection are necessary for an even better exploitation of the test.
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Bordelon, Hali; Ricks, Keersten M.; Pask, Megan E.; Russ, Patricia K.; Solinas, Francesca; Baglia, Mark L.; Short, Philip A.; Nel, Andrew; Blackburn, Jonathan; Dheda, Keertan; Zamudio, Carlos; Cáceres, Tatiana; Wright, David W.; Haselton, Frederick R.; Pettit, April C.
2017-01-01
Urine samples are increasingly used for diagnosing infections including Escherichia coli, Ebola virus, and Zika virus. However, extraction and concentration of nucleic acid biomarkers from urine is necessary for many molecular detection strategies such as polymerase chain reaction (PCR). Since urine samples typically have large volumes with dilute biomarker concentrations making them prone to false negatives, another impediment for urine-based diagnostics is the establishment of appropriate controls particularly to rule out false negatives. In this study, a mouse glyceraldehyde 3-phosphate dehydrogenase (GAPDH) DNA target was added to retrospectively collected urine samples from tuberculosis (TB)-infected and TB-uninfected patients to indicate extraction of intact DNA and removal of PCR inhibitors from urine samples. We tested this design on surrogate urine samples, retrospective 1 milliliter (mL) urine samples from patients in Lima, Peru and retrospective 5 mL urine samples from patients in Cape Town, South Africa. Extraction/PCR control DNA was detectable in 97% of clinical samples with no statistically significant differences among groups. Despite the inclusion of this control, there was no difference in the amount of TB IS6110 Tr-DNA detected between TB-infected and TB-uninfected groups except for samples from known HIV-infected patients. We found a increase in TB IS6110 Tr-DNA between TB/HIV co-infected patients compared to TB-uninfected/HIV-infected patients (N=18, p=0.037). The inclusion of an extraction/PCR control DNA to indicate successful DNA extraction and removal of PCR inhibitors should be easily adaptable as a sample preparation control for other acellular sample types. PMID:28285168
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Malaria rapid diagnostic tests in endemic settings.
Maltha, J; Gillet, P; Jacobs, J
2013-05-01
Malaria rapid diagnostic tests (RDTs) are instrument-free tests that provide results within 20 min and can be used by community health workers. RDTs detect antigens produced by the Plasmodium parasite such as Plasmodium falciparum histidine-rich protein-2 (PfHPR2) and Plasmodium lactate dehydrogenase (pLDH). The accuracy of RDTs for the diagnosis of uncomplicated P. falciparum infection is equal or superior to routine microscopy (but inferior to expert microscopy). Sensitivity for Plasmodium vivax is 75-100%; for Plasmodium ovale and Plasmodium malariae, diagnostic performance is poor. Design limitations of RDTs include poor sensitivity at low parasite densities, susceptibility to the prozone effect (PfHRP2-detecting RDTs), false-negative results due to PfHRP2 deficiency in the case of pfhrp2 gene deletions (PfHRP2-detecting RDTs), cross-reactions between Plasmodium antigens and detection antibodies, false-positive results by other infections and susceptibility to heat and humidity. End-user's errors relate to safety, procedure (delayed reading, incorrect sample and buffer volumes) and interpretation (not recognizing invalid test results, disregarding faint test lines). Withholding antimalarial treatment in the case of negative RDT results tends to be infrequent and tendencies towards over-prescription of antibiotics have been noted. Numerous shortcomings in RDT kits' labelling, instructions for use (correctness and readability) and contents have been observed. The World Health Organization and partners actively address quality assurance of RDTs by comparative testing of RDTs, inspections of manufacturing sites, lot testing and training tools but no formal external quality assessment programme of end-user performance exists. Elimination of malaria requires RDTs with lower detection limits, for which nucleic acid amplification tests are under development. © 2013 The Authors Clinical Microbiology and Infection © 2013 European Society of Clinical Microbiology and Infectious Diseases.
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Currie, A C; Brigic, A; Thomas-Gibson, S; Suzuki, N; Moorghen, M; Jenkins, J T; Faiz, O D; Kennedy, R H
2017-11-01
Previous attempts at sentinel lymph node (SLN) mapping in colon cancer have been compromised by ineffective tracers and the inclusion of advanced disease. This study evaluated the feasibility of fluorescence detection of SLNs with indocyanine green (ICG) for lymphatic mapping in T1/T2 clinically staged colonic malignancy. Consecutive patients with clinical T1/T2 stage colon cancer underwent endoscopic peritumoral submucosal injection of indocyanine green (ICG) for fluorescence detection of SLN using a near-infrared (NIR) camera. All patients underwent laparoscopic complete mesocolic excision surgery. Detection rate and sensitivity of the NIR-ICG technique were the study endpoints. Thirty patients mean age = 68 years [range = 38-80], mean BMI = 26.2 (IQR = 24.7-28.6) were studied. Mesocolic sentinel nodes (median = 3/patient) were detected by fluorescence within the standard resection field in 27/30 patients. Overall, ten patients had lymph node metastases, with one of these patients having a failed SLN procedure. Of the 27 patients with completed SLN mapping, nine patients had histologically positive lymph nodes containing malignancy. 3/9 had positive SLNs with 6 false negatives. In five of these false negative patients, tumours were larger than 35 mm with four also being T3/T4. ICG mapping with NIR fluorescence allowed mesenteric detection of SLNs in clinical T1/T2 stage colonic cancer. CLINICALTRIALS.GOV: ID: NCT01662752. Copyright © 2017 Elsevier Ltd, BASO ~ The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.
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Bordelon, Hali; Ricks, Keersten M; Pask, Megan E; Russ, Patricia K; Solinas, Francesca; Baglia, Mark L; Short, Philip A; Nel, Andrew; Blackburn, Jonathan; Dheda, Keertan; Zamudio, Carlos; Cáceres, Tatiana; Wright, David W; Haselton, Frederick R; Pettit, April C
2017-05-01
Urine samples are increasingly used for diagnosing infections including Escherichia coli, Ebola virus, and Zika virus. However, extraction and concentration of nucleic acid biomarkers from urine is necessary for many molecular detection strategies such as polymerase chain reaction (PCR). Since urine samples typically have large volumes with dilute biomarker concentrations making them prone to false negatives, another impediment for urine-based diagnostics is the establishment of appropriate controls particularly to rule out false negatives. In this study, a mouse glyceraldehyde 3-phosphate dehydrogenase (GAPDH) DNA target was added to retrospectively collected urine samples from tuberculosis (TB)-infected and TB-uninfected patients to indicate extraction of intact DNA and removal of PCR inhibitors from urine samples. We tested this design on surrogate urine samples, retrospective 1milliliter (mL) urine samples from patients in Lima, Peru and retrospective 5mL urine samples from patients in Cape Town, South Africa. Extraction/PCR control DNA was detectable in 97% of clinical samples with no statistically significant differences among groups. Despite the inclusion of this control, there was no difference in the amount of TB IS6110 Tr-DNA detected between TB-infected and TB-uninfected groups except for samples from known HIV-infected patients. We found an increase in TB IS6110 Tr-DNA between TB/HIV co-infected patients compared to TB-uninfected/HIV-infected patients (N=18, p=0.037). The inclusion of an extraction/PCR control DNA to indicate successful DNA extraction and removal of PCR inhibitors should be easily adaptable as a sample preparation control for other acellular sample types. Copyright © 2017 Elsevier B.V. All rights reserved.
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Screening for acute HIV infection in South Africa: finding acute and chronic disease
Bassett, Ingrid V.; Chetty, Senica; Giddy, Janet; Reddy, Shabashini; Bishop, Karen; Lu, Zhigang; Losina, Elena; Freedberg, Kenneth A.; Walensky, Rochelle P.
2010-01-01
Background The yield of screening for acute HIV infection among general medical patients in resource-scarce settings remains unclear. Our objective was to evaluate a strategy of pooled HIV plasma RNA to diagnose acute HIV infection in patients with negative or discordant rapid HIV antibody tests in Durban, South Africa. Methods We prospectively enrolled patients with negative or discordant rapid HIV antibody tests from a routine HIV screening program in an outpatient department in Durban with an HIV prevalence of 48%. Study participants underwent venipuncture for pooled qualitative HIV RNA, and if positive, quantitative RNA, enzyme immunoassay and Western Blot (WB). Patients with negative or indeterminate WB and positive quantitative HIV RNA were considered acutely infected. Those with chronic infection (positive RNA and WB) despite negative or discordant rapid HIV tests were considered false negative rapid antibody tests. Results Nine hundred ninety-four participants were enrolled with either negative (N=976) or discordant (N=18) rapid test results. Eleven (1.1%, 95% CI: 0.6–2.0%) had acute HIV infection. Of the 994 patients, an additional 20 (2.0%, 95% CI: 1.3–.3.1%) had chronic HIV infection (false negative rapid test). Conclusions One percent of outpatients with negative or discordant rapid HIV tests in Durban, South Africa had acute HIV infection readily detectable through pooled serum HIV RNA screening. Pooled RNA testing also identified an additional 2% of patients with chronic HIV infection. HIV RNA screening has the potential to identify both acute and chronic HIV infections that are otherwise missed by standard HIV testing algorithms. PMID:20553336
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Linguistic Determinants of the Difficulty of True-False Test Items
ERIC Educational Resources Information Center
Peterson, Candida C.; Peterson, James L.
1976-01-01
Adults read a prose passage and responded to passages based on it which were either true or false and were phrased either affirmatively or negatively. True negatives yielded most errors, followed in order by false negatives, true affirmatives, and false affirmatives. (Author/RC)
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Automated asteroseismic peak detections
NASA Astrophysics Data System (ADS)
García Saravia Ortiz de Montellano, Andrés; Hekker, S.; Themeßl, N.
2018-05-01
Space observatories such as Kepler have provided data that can potentially revolutionize our understanding of stars. Through detailed asteroseismic analyses we are capable of determining fundamental stellar parameters and reveal the stellar internal structure with unprecedented accuracy. However, such detailed analyses, known as peak bagging, have so far been obtained for only a small percentage of the observed stars while most of the scientific potential of the available data remains unexplored. One of the major challenges in peak bagging is identifying how many solar-like oscillation modes are visible in a power density spectrum. Identification of oscillation modes is usually done by visual inspection that is time-consuming and has a degree of subjectivity. Here, we present a peak-detection algorithm especially suited for the detection of solar-like oscillations. It reliably characterizes the solar-like oscillations in a power density spectrum and estimates their parameters without human intervention. Furthermore, we provide a metric to characterize the false positive and false negative rates to provide further information about the reliability of a detected oscillation mode or the significance of a lack of detected oscillation modes. The algorithm presented here opens the possibility for detailed and automated peak bagging of the thousands of solar-like oscillators observed by Kepler.
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Effects of Sampling and Spatio/Temporal Granularity in Traffic Monitoring on Anomaly Detectability
NASA Astrophysics Data System (ADS)
Ishibashi, Keisuke; Kawahara, Ryoichi; Mori, Tatsuya; Kondoh, Tsuyoshi; Asano, Shoichiro
We quantitatively evaluate how sampling and spatio/temporal granularity in traffic monitoring affect the detectability of anomalous traffic. Those parameters also affect the monitoring burden, so network operators face a trade-off between the monitoring burden and detectability and need to know which are the optimal paramter values. We derive equations to calculate the false positive ratio and false negative ratio for given values of the sampling rate, granularity, statistics of normal traffic, and volume of anomalies to be detected. Specifically, assuming that the normal traffic has a Gaussian distribution, which is parameterized by its mean and standard deviation, we analyze how sampling and monitoring granularity change these distribution parameters. This analysis is based on observation of the backbone traffic, which exhibits spatially uncorrelated and temporally long-range dependence. Then we derive the equations for detectability. With those equations, we can answer the practical questions that arise in actual network operations: what sampling rate to set to find the given volume of anomaly, or, if the sampling is too high for actual operation, what granularity is optimal to find the anomaly for a given lower limit of sampling rate.
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Gotfred-Rasmussen, Helle; Lund, Marianne; Enemark, Heidi L; Erlandsen, Mogens; Petersen, Eskild
2016-03-01
For decades, microscopy of feces after formol-ethylacetate (FEA) concentration and iodine staining has been the routine test for intestinal protozoa. Lately, polymerase chain reaction or fluorescence-labeled parasite-specific antibodies have been introduced, but their place in everyday routine diagnostics has not yet been established. We compared FEA and salt-sugar flotation (SSF) concentration followed by microscopy of iodine-stained concentrate and immunofluorescence assay (IFA) and real-time polymerase chain reaction (qPCR) for detection of Giardia duodenalis in human feces. The median number of Giardia cysts found by FEA in 19 Giardia-positive samples was 50 cysts per gram (CPG), by SSF 350 CPG, by IFA 76,700 CPG, and by qPCR 316,000 CPG. We next tested 455 consecutive samples for presence of Giardia cysts. Using IFA as reference, qPCR had a sensitivity of 91%, specificity of 95.1%, a false-positive rate of 50%, a false-negative rate of 0.48%, a positive predictive value of 50%, and a negative predictive value of 99.5%. In conclusion, qPCR and IFA were significantly more sensitive than microscopy of iodine-stained concentrates using either FEA or SSF. We suggest, when using qPCR, that positive samples are verified by IFA to prevent false-positive results. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.
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Weinstein, Susan P.; McDonald, Elizabeth S.; Conant, Emily F.
2016-01-01
Digital breast tomosynthesis (DBT) represents a valuable addition to breast cancer screening by decreasing recall rates while increasing cancer detection rates. The increased accuracy achieved with DBT is due to the quasi–three-dimensional format of the reconstructed images and the ability to “scroll through” breast tissue in the reconstructed images, thereby reducing the effect of tissue superimposition found with conventional planar digital mammography. The margins of both benign and malignant lesions are more conspicuous at DBT, which allows improved lesion characterization, increased reader confidence, and improved screening outcomes. However, even with the improvements in accuracy achieved with DBT, there remain differences in breast cancer conspicuity by mammographic view. Early data suggest that breast cancers may be more conspicuous on craniocaudal (CC) views than on mediolateral oblique (MLO) views. While some very laterally located breast cancers may be visualized on only the MLO view, the increased conspicuity of cancers on the CC view compared with the MLO view suggests that DBT screening should be performed with two-view imaging. Even with the improved conspicuity of lesions at DBT, there may still be false-negative studies. Subtle lesions seen on only one view may be discounted, and dense and/or complex tissue patterns may make some cancers occult or extremely difficult to detect. Therefore, radiologists should be cognizant of both perceptual and cognitive errors to avoid potential pitfalls in lesion detection and characterization. ©RSNA, 2016 Online supplemental material is available for this article. PMID:27715711
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A screening questionnaire for convulsive seizures: A three-stage field-validation in rural Bolivia.
Giuliano, Loretta; Cicero, Calogero Edoardo; Crespo Gómez, Elizabeth Blanca; Padilla, Sandra; Bruno, Elisa; Camargo, Mario; Marin, Benoit; Sofia, Vito; Preux, Pierre-Marie; Strohmeyer, Marianne; Bartoloni, Alessandro; Nicoletti, Alessandra
2017-01-01
Epilepsy is one of the most common neurological diseases in Latin American Countries (LAC) and epilepsy associated with convulsive seizures is the most frequent type. Therefore, the detection of convulsive seizures is a priority, but a validated Spanish-language screening tool to detect convulsive seizures is not available. We performed a field validation to evaluate the accuracy of a Spanish-language questionnaire to detect convulsive seizures in rural Bolivia using a three-stage design. The questionnaire was also administered face-to-face, using a two-stage design, to evaluate the difference in accuracy. The study was carried out in the rural communities of the Gran Chaco region. The questionnaire consists of a single screening question directed toward the householders and a confirmatory section administered face-to-face to the index case. Positive subjects underwent a neurological examination to detect false positive and true positive subjects. To estimate the proportion of false negative, a random sample of about 20% of the screened negative underwent a neurological evaluation. 792 householders have been interviewed representing a population of 3,562 subjects (52.2% men; mean age 24.5 ± 19.7 years). We found a sensitivity of 76.3% (95% CI 59.8-88.6) with a specificity of 99.6% (95% CI 99.4-99.8). The two-stage design showed only a slightly higher sensitivity respect to the three-stage design. Our screening tool shows a good accuracy and can be easily used by trained health workers to quickly screen the population of the rural communities of LAC through the householders using a three-stage design.
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A hybrid approach for text detection in natural scenes
NASA Astrophysics Data System (ADS)
Wang, Runmin; Sang, Nong; Wang, Ruolin; Kuang, Xiaoqin
2013-10-01
In this paper, a hybrid approach is proposed to detect texts in natural scenes. It is performed by the following steps: Firstly, the edge map and the text saliency region are obtained. Secondly, the text candidate regions are detected by connected components (CC) based method and are identified by an off-line trained HOG classifier. And then, the remaining CCs are grouped into text lines with some heuristic strategies to make up for the false negatives. Finally, the text lines are broken into separate words. The performance of the proposed approach is evaluated on the location detection database of ICDAR 2003 robust reading competition. Experimental results demonstrate the validity of our approach and are competitive with other state-of-the-art algorithms.
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Antunes, Bárbara; Murtagh, Fliss; Bausewein, Claudia; Harding, Richard; Higginson, Irene J
2015-02-01
Depression is common among patients with advanced disease but often difficult to detect. To assess the Palliative care Outcome Scale (POS) (10 items) against the Geriatric Depression Scale (GDS)-10 total score and the Hospital Anxiety and Depression Scale (HADS)-Depression subscale total score and determine if the POS has appropriate items to screen for depression among people with advanced disease. This was a secondary analysis performed on five studies. Four psychometric properties were assessed: data quality, scaling assumptions, acceptability, and internal consistency (reliability). Receiver operating characteristic (ROC) curves were used to determine the area under the curve. Sensitivity, specificity, positive and negative predictive values, false positive and negative rates, and positive and negative likelihood ratios were computed. The overall sample had 416 patients from Germany and England: 144 had cancer and 267 had nonmalignant conditions. Prevalence of depression across the sample was 17.5%. Floor and ceiling effects were rare. Cronbach's alpha coefficients for POS items 7 and 8 summed, GDS-10 and HADS-Depression items varied: 0.61 (heart failure) and 0.80 (cancer). Two items combined (Item 7-feeling depressed and Item 8-feeling good about yourself) consistently presented the highest area under the ROC curve, ranging from 0.76 (95% CI 0.60, 0.93) (Germany, lung cancer) to 0.97 (95% CI 0.91, 1.0) (heart failure), highest negative predictive value, and lowest false negative rate. For the overall sample, the cutoff 2/3 presented a negative predictive value of 89.4% (95% CI 84.7, 92.8) and false negative rate of 10.6 (95% CI 7.2, 15.3). POS items 7 and 8 summed are potentially useful to screen for depression in advanced disease populations. Copyright © 2015 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.
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Kamugisha, M L; Msangeni, H; Beale, E; Malecela, E K; Akida, J; Ishengoma, D R S; Lemnge, M M
2008-01-01
Malaria is a major public health problem particularly in rural Sub-Saharan Africa. In most urban areas, malaria transmission intensity is low thus monitoring trends using reliable tools is crucial to provide vital information for future management of the disease. Rapid diagnostic tests (RDT) such as Paracheck Pf are now increasingly adopted for Plasmodium falciparum malaria diagnosis and are advantageous and cost effective alternative to microscopy. This cross sectional survey was carried out during June 2005 to determine the prevalence of malaria in an urban setting and compare microscopy diagnosis versus Paracheck Pf for detecting Plasmodium falciparum. Blood samples from a total of 301 children (< 10 years) attending outpatient clinic at Makorora Health Centre, in Tanga, Tanzania were examined for the presence of malaria. Twenty-nine (9.6%) of the children were positive to malaria by microscopy while 30 (10.0%) were positive by Paracheck test. Three out of 30 positive cases detected by Paracheck were negative by microscopy; thus considered to be false positive results. For the 271 Paracheck Pf negative cases, 2 were positive by microscopy; yielding 2 false negative results. Paracheck Pf sensitivity and specificity were 93.1% and 98.9%, respectively. P. falciparum was the only malarial species observed among the 29 microscopy positive cases. The prevalence of anaemia among the children was 53.16%. These findings indicate a low prevalence of malaria in Tanga City and that Paracheck Pf can be an effective tool for malaria diagnosis.
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Clinical use of MRI for the evaluation of acute appendicitis during pregnancy.
Patel, Darshan; Fingard, Jordan; Winters, Sean; Low, Gavin
2017-07-01
The purpose of this study was to determine the diagnostic accuracy of MRI for detecting acute appendicitis in pregnancy in a multi-institution study involving general body MR readers with no specific expertise in MR imaging of the pregnant patient. Retrospective review of MRI examinations on PACS in 42 pregnant patients was evaluated for acute right lower quadrant pain. Three fellowship-trained general body radiologists analyzed the MRI examinations in consensus and attempted to localize the appendix, assess for features of appendicitis, and exclude alternative etiologies for the right lower quadrant pain. Of the 42 MRI examinations, the readers noted 6 cases of acute appendicitis, 16 cases of a normal appendix, and 20 cases involving non-visualization of the appendix but where there were no secondary features of acute appendicitis. Based on the surgical data and clinical follow-up, there were 3 true-positive cases, 3 false-positive cases, 34 true-negative cases, and 2 false-negative cases of acute appendicitis on MRI. This yielded an accuracy of 88.1%, sensitivity of 60%, specificity of 91.9%, positive predictive value of 50%, and negative predictive value of 94.4% for the detection of acute appendicitis in the pregnant patient on MRI. Alternative etiologies for the right lower quadrant pain on MRI included torsion of an ovarian dermoid in 1 case and pyelonephritis in 1 case. MRI is an excellent modality for excluding acute appendicitis in pregnant patients presenting with right lower quadrant pain.
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Fusion Imaging: A Novel Staging Modality in Testis Cancer
Sterbis, Joseph R.; Rice, Kevin R.; Javitt, Marcia C.; Schenkman, Noah S.; Brassell, Stephen A.
2010-01-01
Objective: Computed tomography and chest radiographs provide the standard imaging for staging, treatment, and surveillance of testicular germ cell neoplasms. Positron emission tomography has recently been utilized for staging, but is somewhat limited in its ability to provide anatomic localization. Fusion imaging combines the metabolic information provided by positron emission tomography with the anatomic precision of computed tomography. To the best of our knowledge, this represents the first study of the effectiveness using fusion imaging in evaluation of patients with testis cancer. Methods: A prospective study of 49 patients presenting to Walter Reed Army Medical Center with testicular cancer from 2003 to 2009 was performed. Fusion imaging was compared with conventional imaging, tumor markers, pathologic results, and clinical follow-up. Results: There were 14 true positives, 33 true negatives, 1 false positive, and 1 false negative. Sensitivity, specificity, positive predictive value, and negative predictive value were 93.3, 97.0, 93.3, and 97.0% respectively. In 11 patient scenarios, fusion imaging differed from conventional imaging. Utility was found in superior lesion detection compared to helical computed tomography due to anatomical/functional image co-registration, detection of micrometastasis in lymph nodes (pathologic nodes < 1cm), surveillance for recurrence post-chemotherapy, differentiating fibrosis from active disease in nodes < 2.5cm, and acting as a quality assurance measure to computed tomography alone. Conclusions: In addition to demonstrating a sensitivity and specificity comparable or superior to conventional imaging, fusion imaging shows promise in providing additive data that may assist in clinical decision-making. PMID:21103077
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Fusion imaging: a novel staging modality in testis cancer.
Sterbis, Joseph R; Rice, Kevin R; Javitt, Marcia C; Schenkman, Noah S; Brassell, Stephen A
2010-11-05
Computed tomography and chest radiographs provide the standard imaging for staging, treatment, and surveillance of testicular germ cell neoplasms. Positron emission tomography has recently been utilized for staging, but is somewhat limited in its ability to provide anatomic localization. Fusion imaging combines the metabolic information provided by positron emission tomography with the anatomic precision of computed tomography. To the best of our knowledge, this represents the first study of the effectiveness using fusion imaging in evaluation of patients with testis cancer. A prospective study of 49 patients presenting to Walter Reed Army Medical Center with testicular cancer from 2003 to 2009 was performed. Fusion imaging was compared with conventional imaging, tumor markers, pathologic results, and clinical follow-up. There were 14 true positives, 33 true negatives, 1 false positive, and 1 false negative. Sensitivity, specificity, positive predictive value, and negative predictive value were 93.3, 97.0, 93.3, and 97.0% respectively. In 11 patient scenarios, fusion imaging differed from conventional imaging. Utility was found in superior lesion detection compared to helical computed tomography due to anatomical/functional image co-registration, detection of micrometastasis in lymph nodes (pathologic nodes < 1cm), surveillance for recurrence post-chemotherapy, differentiating fibrosis from active disease in nodes < 2.5cm, and acting as a quality assurance measure to computed tomography alone. In addition to demonstrating a sensitivity and specificity comparable or superior to conventional imaging, fusion imaging shows promise in providing additive data that may assist in clinical decision-making.
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Tejada-Palacios, P; Zarratea, L; Moral, M; de la Cruz-Bértolo, J
2015-08-01
To determine the performance of RetCam vs. binocular ophthalmoscopy (BIO) in a screening program for retinopathy of prematurity (ROP). Observational comparative study with prospective data collection. Examinations with RetCam (n=169) were performed on 83 infants included in a screening program for ROP and stored for analysis at a later stage. An experienced ophthalmologist examined the ocular fundus with binocular indirect ophthalmoscopy (BIO). The RetCam images were assessed for the presence of ROP, zone, grade, and presence of plus disease. RetCam and BIO data were compared by visually to estimate sensitivity, specificity, positive (VPP) and negative (VPN) predictive values. ROP disease was detected in 108 eyes with BIO, and in 74 with RetCam. Out of 306 eyes examined with RetCam, false negative results were found in 34 eyes, with no false positives. Sensitivity of RetCam exam vs. BIO was 0.68, and specificity was 0.99. Positive predictive value was 0.93 and negative predictive value was 0.85. All 34 ROP cases not detected with RetCam were in zone III or outer zone II. They were all mild and regressed spontaneously. No threshold ROP was missed with RetCam. Binocular indirect ophthalmoscopy is the reference method for the diagnosis of ROP. RetCam may be used as an alternative for ROP screening. Copyright © 2010 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.
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Clare, John; McKinney, Shawn T.; DePue, John E.; Loftin, Cynthia S.
2017-01-01
It is common to use multiple field sampling methods when implementing wildlife surveys to compare method efficacy or cost efficiency, integrate distinct pieces of information provided by separate methods, or evaluate method-specific biases and misclassification error. Existing models that combine information from multiple field methods or sampling devices permit rigorous comparison of method-specific detection parameters, enable estimation of additional parameters such as false-positive detection probability, and improve occurrence or abundance estimates, but with the assumption that the separate sampling methods produce detections independently of one another. This assumption is tenuous if methods are paired or deployed in close proximity simultaneously, a common practice that reduces the additional effort required to implement multiple methods and reduces the risk that differences between method-specific detection parameters are confounded by other environmental factors. We develop occupancy and spatial capture–recapture models that permit covariance between the detections produced by different methods, use simulation to compare estimator performance of the new models to models assuming independence, and provide an empirical application based on American marten (Martes americana) surveys using paired remote cameras, hair catches, and snow tracking. Simulation results indicate existing models that assume that methods independently detect organisms produce biased parameter estimates and substantially understate estimate uncertainty when this assumption is violated, while our reformulated models are robust to either methodological independence or covariance. Empirical results suggested that remote cameras and snow tracking had comparable probability of detecting present martens, but that snow tracking also produced false-positive marten detections that could potentially substantially bias distribution estimates if not corrected for. Remote cameras detected marten individuals more readily than passive hair catches. Inability to photographically distinguish individual sex did not appear to induce negative bias in camera density estimates; instead, hair catches appeared to produce detection competition between individuals that may have been a source of negative bias. Our model reformulations broaden the range of circumstances in which analyses incorporating multiple sources of information can be robustly used, and our empirical results demonstrate that using multiple field-methods can enhance inferences regarding ecological parameters of interest and improve understanding of how reliably survey methods sample these parameters.
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A two-hypothesis approach to establishing a life detection/biohazard protocol for planetary samples
NASA Astrophysics Data System (ADS)
Conley, Catharine; Steele, Andrew
2016-07-01
The COSPAR policy on performing a biohazard assessment on samples brought from Mars to Earth is framed in the context of a concern for false-positive results. However, as noted during the 2012 Workshop for Life Detection in Samples from Mars (ref. Kminek et al., 2014), a more significant concern for planetary samples brought to Earth is false-negative results, because an undetected biohazard could increase risk to the Earth. This is the reason that stringent contamination control must be a high priority for all Category V Restricted Earth Return missions. A useful conceptual framework for addressing these concerns involves two complementary 'null' hypotheses: testing both of them, together, would allow statistical and community confidence to be developed regarding one or the other conclusion. As noted above, false negatives are of primary concern for safety of the Earth, so the 'Earth Safety null hypothesis' -- that must be disproved to assure low risk to the Earth from samples introduced by Category V Restricted Earth Return missions -- is 'There is native life in these samples.' False positives are of primary concern for Astrobiology, so the 'Astrobiology null hypothesis' -- that must be disproved in order to demonstrate the existence of extraterrestrial life is 'There is no life in these samples.' The presence of Earth contamination would render both of these hypotheses more difficult to disprove. Both these hypotheses can be tested following a strict science protocol; analyse, interprete, test the hypotheses and repeat. The science measurements undertaken are then done in an iterative fashion that responds to discovery with both hypotheses testable from interpretation of the scientific data. This is a robust, community involved activity that ensures maximum science return with minimal sample use.
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Nandipati, Kalyana C; Allamaneni, Shyam; Kakarla, Ravindra; Wong, Alfredo; Richards, Neil; Satterfield, James; Turner, James W; Sung, Kae-Jae
2011-05-01
Early identification of pneumothorax is crucial to reduce the mortality in critically injured patients. The objective of our study is to investigate the utility of surgeon performed extended focused assessment with sonography for trauma (EFAST) in the diagnosis of pneumothorax. We prospectively analysed 204 trauma patients in our level I trauma center over a period of 12 (06/2007-05/2008) months in whom EFAST was performed. The patients' demographics, type of injury, clinical examination findings (decreased air entry), CXR, EFAST and CT scan findings were entered into the data base. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated. Of 204 patients (mean age--43.01+/-19.5 years, sex--male 152, female 52) 21 (10.3%) patients had pneumothorax. Of 21 patients who had pneumothorax 12 were due to blunt trauma and 9 were due to penetrating trauma. The diagnosis of pneumothorax in 204 patients demonstrated the following: clinical examination was positive in 17 patients (true positive in 13/21, 62%; 4 were false positive and 8 were false negative), CXR was positive in 16 (true positive in 15/19, 79%; 1 false positive, 4 missed and 2 CXR not performed before chest tube) patients and EFAST was positive in 21 patients (20 were true positive [95.2%], 1 false positive and 1 false negative). In diagnosing pneumothorax EFAST has significantly higher sensitivity compared to the CXR (P=0.02). Surgeon performed trauma room extended FAST is simple and has higher sensitivity compared to the chest X-ray and clinical examination in detecting pneumothorax. Published by Elsevier Ltd.
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Dharan, Nila J; Blakemore, Robert; Sloutsky, Alex; Kaur, Devinder; Alexander, Richard C; Ghajar, Minoo; Musser, Kimberlee A; Escuyer, Vincent E; Rowlinson, Marie-Claire; Crowe, Susanne; Laniado-Laborin, Rafael; Valli, Eloise; Nabeta, Pamela; Johnson, Pamela; Alland, David
2016-12-20
The Xpert ® MTB/RIF (Xpert) assay is a rapid PCR-based assay for the detection of Mycobacterium tuberculosis complex DNA (MTBc) and mutations associated with rifampin resistance (RIF). An updated version introduced in 2011, the G4 Xpert, included modifications to probe B and updated analytic software. An analytical study was performed to assess Xpert detection of mutations associated with rifampin resistance in rifampin-susceptible and -resistant isolates. A clinical study was performed in which specimens from US and non-US persons suspected of tuberculosis (TB) were tested to determine Xpert performance characteristics. All specimens underwent smear microscopy, mycobacterial culture, conventional drug-susceptibility testing and Xpert testing; DNA from isolates with discordant rifampin resistance results was sequenced. Among 191 laboratory-prepared isolates in the analytical study, Xpert sensitivity for detection of rifampin resistance associated mutations was 97.7% and specificity was 90.8%, which increased to 99.0% after DNA sequencing analysis of the discordant samples. Of the 1,096 subjects in the four clinical studies, 49% were from the US. Overall, Xpert detected MTBc in 439 of 468 culture-positive specimens for a sensitivity of 93.8% (95% confidence interval [CI]: 91.2%-95.7%) and did not detect MTBc in 620 of 628 culture-negative specimens for a specificity of 98.7% (95% CI: 97.5%-99.4%). Sensitivity was 99.7% among smear-positive cases, and 76.1% among smear-negative cases. Non-determinate MTBc detection and false-positive RIF resistance results were low (1.2 and 0.9%, respectively). The updated Xpert assay retained the high sensitivity and specificity of the previous assay versions and demonstrated low rates of non-determinate and RIF resistance false positive results.
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Data integrity systems for organ contours in radiation therapy planning.
Shah, Veeraj P; Lakshminarayanan, Pranav; Moore, Joseph; Tran, Phuoc T; Quon, Harry; Deville, Curtiland; McNutt, Todd R
2018-06-12
The purpose of this research is to develop effective data integrity models for contoured anatomy in a radiotherapy workflow for both real-time and retrospective analysis. Within this study, two classes of contour integrity models were developed: data driven models and contiguousness models. The data driven models aim to highlight contours which deviate from a gross set of contours from similar disease sites and encompass the following regions of interest (ROI): bladder, femoral heads, spinal cord, and rectum. The contiguousness models, which individually analyze the geometry of contours to detect possible errors, are applied across many different ROI's and are divided into two metrics: Extent and Region Growing over volume. After analysis, we found that 70% of detected bladder contours were verified as suspicious. The spinal cord and rectum models verified that 73% and 80% of contours were suspicious respectively. The contiguousness models were the most accurate models and the Region Growing model was the most accurate submodel. 100% of the detected noncontiguous contours were verified as suspicious, but in the cases of spinal cord, femoral heads, bladder, and rectum, the Region Growing model detected additional two to five suspicious contours that the Extent model failed to detect. When conducting a blind review to detect false negatives, it was found that all the data driven models failed to detect all suspicious contours. The Region Growing contiguousness model produced zero false negatives in all regions of interest other than prostate. With regards to runtime, the contiguousness via extent model took an average of 0.2 s per contour. On the other hand, the region growing method had a longer runtime which was dependent on the number of voxels in the contour. Both contiguousness models have potential for real-time use in clinical radiotherapy while the data driven models are better suited for retrospective use. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.
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Stürenburg, Enno; Lang, Melanie; Horstkotte, Matthias A; Laufs, Rainer; Mack, Dietrich
2004-11-01
We aimed to assess the performance of the MicroScan ESBL plus confirmation panel using a series of 87 oxyimino-cephalosporin-resistant Gram-negative bacilli of various species. Organisms tested included 57 extended-spectrum beta-lactamase (ESBL) strains comprising Enterobacter aerogenes (3), Enterobacter cloacae (10), Escherichia coli (11), Klebsiella pneumoniae (26), Klebsiella oxytoca (3) and Proteus mirabilis (4). Also included were 30 strains resistant to oxyimino cephalosporins but lacking ESBLs, which were characterized with other resistance mechanisms, such as inherent clavulanate susceptibility in Acinetobacter spp. (4), hyperproduction of AmpC enzyme in Citrobacter freundii (2), E. aerogenes (3), E. cloacae (3), E. coli (4), Hafnia alvei (1) and Morganella morganii (1), production of plasmid-mediated AmpC beta-lactamase in K. pneumoniae (3) and E. coli (3) or hyperproduction of K1 enzyme in K. oxytoca (6). The MicroScan MIC-based clavulanate synergy correctly classified 50 of 57 ESBL strains as ESBL-positive and 23 of 30 non-ESBL strains as ESBL-negative (yielding a sensitivity of 88% and a specificity of 76.7%, respectively). False negatives among ESBL producers were highest with Enterobacter spp. due to masking interactions between ESBL and AmpC beta-lactamases. False-positive classifications occurred in two Acinetobacter spp., one E. coli producing plasmid-mediated AmpC beta-lactamase and two K. oxytoca hyperproducing their chromosomal K1 beta-lactamase. The MicroScan clavulanate synergy test proved to be a valuable tool for ESBL confirmation. However, this test has limitations in detecting ESBLs in Enterobacter spp. and in discriminating ESBL-related resistance from the K1 enzyme and from inherent clavulanate susceptibility in Acinetobacter spp.
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A statistical method for the detection of variants from next-generation resequencing of DNA pools.
Bansal, Vikas
2010-06-15
Next-generation sequencing technologies have enabled the sequencing of several human genomes in their entirety. However, the routine resequencing of complete genomes remains infeasible. The massive capacity of next-generation sequencers can be harnessed for sequencing specific genomic regions in hundreds to thousands of individuals. Sequencing-based association studies are currently limited by the low level of multiplexing offered by sequencing platforms. Pooled sequencing represents a cost-effective approach for studying rare variants in large populations. To utilize the power of DNA pooling, it is important to accurately identify sequence variants from pooled sequencing data. Detection of rare variants from pooled sequencing represents a different challenge than detection of variants from individual sequencing. We describe a novel statistical approach, CRISP [Comprehensive Read analysis for Identification of Single Nucleotide Polymorphisms (SNPs) from Pooled sequencing] that is able to identify both rare and common variants by using two approaches: (i) comparing the distribution of allele counts across multiple pools using contingency tables and (ii) evaluating the probability of observing multiple non-reference base calls due to sequencing errors alone. Information about the distribution of reads between the forward and reverse strands and the size of the pools is also incorporated within this framework to filter out false variants. Validation of CRISP on two separate pooled sequencing datasets generated using the Illumina Genome Analyzer demonstrates that it can detect 80-85% of SNPs identified using individual sequencing while achieving a low false discovery rate (3-5%). Comparison with previous methods for pooled SNP detection demonstrates the significantly lower false positive and false negative rates for CRISP. Implementation of this method is available at http://polymorphism.scripps.edu/~vbansal/software/CRISP/.
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Working memory affects false memory production for emotional events.
Mirandola, Chiara; Toffalini, Enrico; Ciriello, Alfonso; Cornoldi, Cesare
2017-01-01
Whereas a link between working memory (WM) and memory distortions has been demonstrated, its influence on emotional false memories is unclear. In two experiments, a verbal WM task and a false memory paradigm for negative, positive or neutral events were employed. In Experiment 1, we investigated individual differences in verbal WM and found that the interaction between valence and WM predicted false recognition, with negative and positive material protecting high WM individuals against false remembering; the beneficial effect of negative material disappeared in low WM participants. In Experiment 2, we lowered the WM capacity of half of the participants with a double task request, which led to an overall increase in false memories; furthermore, consistent with Experiment 1, the increase in negative false memories was larger than that of neutral or positive ones. It is concluded that WM plays a critical role in determining false memory production, specifically influencing the processing of negative material.
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Peeters, Bart; Herijgers, Paul; Beuselinck, Kurt; Peetermans, Willy E.; Herregods, Marie-Christin
2016-01-01
Identification of the causative pathogen of infective endocarditis (IE) is crucial for adequate management and therapy. A broad-range PCR-electrospray ionization mass spectrometry (PCR-ESI-MS) technique was compared with broad-spectrum 16S rRNA PCR and amplicon sequencing (16S rRNA PCR) for the detection of bacterial pathogens in 40 heart valves obtained from 34 definite infective endocarditis patients according to the modified Duke criteria and six nonendocarditis patients. Concordance between the two molecular techniques was 98% for being positive or negative, 97% for concordant identification up to the genus level, and 77% for concordant identification up to the species level. Sensitivity for detecting the causative pathogen (up to the genus level) in excised heart valves was 88% for 16S rRNA PCR and 85% for PCR-ESI-MS; the specificity was 83% for both methods. The two molecular techniques were significantly more sensitive than valve culture (18%) and accurately identified bacteria in excised heart valves. In eight patients with culture-negative IE, the following results were obtained: concordant detection of Coxiella burnetii (n = 2), Streptococcus gallolyticus (n = 1), Propionibacterium acnes (n = 1), and viridans group streptococci (n = 1) by both molecular tests, detection of P. acnes by PCR-ESI-MS whereas the 16S rRNA PCR was negative (n = 1), and a false-negative result by both molecular techniques (n = 2). In one case of IE caused by viridans streptococci, PCR-ESI-MS was positive for Enterococcus spp. The advantages of PCR-ESI-MS compared to 16S rRNA PCR are its automated workflow and shorter turnaround times. PMID:27629895
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Improving Cyber-Security of Smart Grid Systems via Anomaly Detection and Linguistic Domain Knowledge
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ondrej Linda; Todd Vollmer; Milos Manic
The planned large scale deployment of smart grid network devices will generate a large amount of information exchanged over various types of communication networks. The implementation of these critical systems will require appropriate cyber-security measures. A network anomaly detection solution is considered in this work. In common network architectures multiple communications streams are simultaneously present, making it difficult to build an anomaly detection solution for the entire system. In addition, common anomaly detection algorithms require specification of a sensitivity threshold, which inevitably leads to a tradeoff between false positives and false negatives rates. In order to alleviate these issues, thismore » paper proposes a novel anomaly detection architecture. The designed system applies the previously developed network security cyber-sensor method to individual selected communication streams allowing for learning accurate normal network behavior models. Furthermore, the developed system dynamically adjusts the sensitivity threshold of each anomaly detection algorithm based on domain knowledge about the specific network system. It is proposed to model this domain knowledge using Interval Type-2 Fuzzy Logic rules, which linguistically describe the relationship between various features of the network communication and the possibility of a cyber attack. The proposed method was tested on experimental smart grid system demonstrating enhanced cyber-security.« less
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The impact of negative affect on reality discrimination.
Smailes, David; Meins, Elizabeth; Fernyhough, Charles
2014-09-01
People who experience auditory hallucinations tend to show weak reality discrimination skills, so that they misattribute internal, self-generated events to an external, non-self source. We examined whether inducing negative affect in healthy young adults would increase their tendency to make external misattributions on a reality discrimination task. Participants (N = 54) received one of three mood inductions (one positive, two negative) and then performed an auditory signal detection task to assess reality discrimination. Participants who received either of the two negative inductions made more false alarms, but not more hits, than participants who received the neutral induction, indicating that negative affect makes participants more likely to misattribute internal, self-generated events to an external, non-self source. These findings are drawn from an analogue sample, and research that examines whether negative affect also impairs reality discrimination in patients who experience auditory hallucinations is required. These findings show that negative affect disrupts reality discrimination and suggest one way in which negative affect may lead to hallucinatory experiences. Copyright © 2014 Elsevier Ltd. All rights reserved.
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Miles, Anne; Rodrigues, Vania; Sevdalis, Nick
2013-11-01
To examine the impact of numeric risk information about false negative (FN) and false positive (FP) rates in faecal occult blood testing (FOBt) on attitudes towards screening. 95 people aged 45-59, living in England, read 6 hypothetical vignettes presented online about the use of FOB testing to detect bowel cancer, in which information about FN and FP rates was systematically varied. Both verbal and numeric FN risk information reduced people's interest in screening compared with no FN information. Numeric FN risk information reduced people's perceptions of screening effectiveness and lowered perceived trust in the results of screening compared with both verbal FN information and no FN information. FP information did not affect attitudes towards FOB testing. There was limited evidence that FN information reduced interest and perceptions of screening effectiveness more in educated groups. Numeric FN risk information decreased people's perceptions of screening effectiveness and trust in the results of screening but did not affect people's interest in screening anymore than verbal FN risk information. Numeric FN information could be added to patient information without affecting interest in screening, although this needs to be replicated in a larger, more representative sample. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
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False positives complicate ancient pathogen identifications using high-throughput shotgun sequencing
2014-01-01
Background Identification of historic pathogens is challenging since false positives and negatives are a serious risk. Environmental non-pathogenic contaminants are ubiquitous. Furthermore, public genetic databases contain limited information regarding these species. High-throughput sequencing may help reliably detect and identify historic pathogens. Results We shotgun-sequenced 8 16th-century Mixtec individuals from the site of Teposcolula Yucundaa (Oaxaca, Mexico) who are reported to have died from the huey cocoliztli (‘Great Pestilence’ in Nahautl), an unknown disease that decimated native Mexican populations during the Spanish colonial period, in order to identify the pathogen. Comparison of these sequences with those deriving from the surrounding soil and from 4 precontact individuals from the site found a wide variety of contaminant organisms that confounded analyses. Without the comparative sequence data from the precontact individuals and soil, false positives for Yersinia pestis and rickettsiosis could have been reported. Conclusions False positives and negatives remain problematic in ancient DNA analyses despite the application of high-throughput sequencing. Our results suggest that several studies claiming the discovery of ancient pathogens may need further verification. Additionally, true single molecule sequencing’s short read lengths, inability to sequence through DNA lesions, and limited ancient-DNA-specific technical development hinder its application to palaeopathology. PMID:24568097
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Saavedra, Miguel; Zulantay, Inés; Apt, Werner; Martínez, Gabriela; Rojas, Antonio; Rodríguez, Jorge
2013-01-01
We evaluate the elimination of the microscopic stage of conventional xenodiagnosis (XD) to optimize the parasitological diagnosis of Trypanosoma cruzi in chronic Chagas disease. To this purpose we applied under informed consent two XD cages to 150 Chilean chronic chagasic patients. The fecal samples (FS) of the triatomines at 30, 60 and 90 days post feeding were divided into two parts: in one a microscopic search for mobile trypomastigote and/or epimastigote forms was performed. In the other part, DNA extraction-purification for PCR directed to the conserved region of kDNA minicircles of trypanosomes (PCR-XD), without previous microscopic observation was done. An XD was considered positive when at least one mobile T. cruzi parasite in any one of three periods of incubation was observed, whereas PCR-XD was considered positive when the 330 bp band specific for T. cruzi was detected. 25 of 26 cases with positive conventional XD were PCR-XD positive (concordance 96.2%), whereas 85 of 124 cases with negative conventional XD were positive by PCR-XD (68.5%). Human chromosome 12 detected by Real-time PCR used as exogenous internal control of PCR-XD reaction allowed to discounting of PCR inhibition and false negative in 40 cases with negative PCR-XD. PCR-XD performed without previous microscopic observation is a useful tool for detection of viable parasites with higher efficiency then conventional XD.
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Face detection assisted auto exposure: supporting evidence from a psychophysical study
NASA Astrophysics Data System (ADS)
Jin, Elaine W.; Lin, Sheng; Dharumalingam, Dhandapani
2010-01-01
Face detection has been implemented in many digital still cameras and camera phones with the promise of enhancing existing camera functions (e.g. auto exposure) and adding new features to cameras (e.g. blink detection). In this study we examined the use of face detection algorithms in assisting auto exposure (AE). The set of 706 images, used in this study, was captured using Canon Digital Single Lens Reflex cameras and subsequently processed with an image processing pipeline. A psychophysical study was performed to obtain optimal exposure along with the upper and lower bounds of exposure for all 706 images. Three methods of marking faces were utilized: manual marking, face detection algorithm A (FD-A), and face detection algorithm B (FD-B). The manual marking method found 751 faces in 426 images, which served as the ground-truth for face regions of interest. The remaining images do not have any faces or the faces are too small to be considered detectable. The two face detection algorithms are different in resource requirements and in performance. FD-A uses less memory and gate counts compared to FD-B, but FD-B detects more faces and has less false positives. A face detection assisted auto exposure algorithm was developed and tested against the evaluation results from the psychophysical study. The AE test results showed noticeable improvement when faces were detected and used in auto exposure. However, the presence of false positives would negatively impact the added benefit.
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Le Strat, Yann
2017-01-01
The objective of this paper is to evaluate a panel of statistical algorithms for temporal outbreak detection. Based on a large dataset of simulated weekly surveillance time series, we performed a systematic assessment of 21 statistical algorithms, 19 implemented in the R package surveillance and two other methods. We estimated false positive rate (FPR), probability of detection (POD), probability of detection during the first week, sensitivity, specificity, negative and positive predictive values and F1-measure for each detection method. Then, to identify the factors associated with these performance measures, we ran multivariate Poisson regression models adjusted for the characteristics of the simulated time series (trend, seasonality, dispersion, outbreak sizes, etc.). The FPR ranged from 0.7% to 59.9% and the POD from 43.3% to 88.7%. Some methods had a very high specificity, up to 99.4%, but a low sensitivity. Methods with a high sensitivity (up to 79.5%) had a low specificity. All methods had a high negative predictive value, over 94%, while positive predictive values ranged from 6.5% to 68.4%. Multivariate Poisson regression models showed that performance measures were strongly influenced by the characteristics of time series. Past or current outbreak size and duration strongly influenced detection performances. PMID:28715489
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Storbeck, Justin
2013-01-01
I investigated whether negative affective states enhance encoding of and memory for item-specific information reducing false memories. Positive, negative, and neutral moods were induced, and participants then completed a Deese-Roediger-McDermott (DRM) false-memory task. List items were presented in unique spatial locations or unique fonts to serve as measures for item-specific encoding. The negative mood conditions had more accurate memories for item-specific information, and they also had fewer false memories. The final experiment used a manipulation that drew attention to distinctive information, which aided learning for DRM words, but also promoted item-specific encoding. For the condition that promoted item-specific encoding, false memories were reduced for positive and neutral mood conditions to a rate similar to that of the negative mood condition. These experiments demonstrated that negative affective cues promote item-specific processing reducing false memories. People in positive and negative moods encode events differently creating different memories for the same event.
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Detecting Candida albicans in human milk.
Morrill, Jimi Francis; Pappagianis, Demosthenes; Heinig, M Jane; Lönnerdal, Bo; Dewey, Kathryn G
2003-01-01
Procedures for diagnosis of mammary candidosis, including laboratory confirmation, are not well defined. Lactoferrin present in human milk can inhibit growth of Candida albicans, thereby limiting the ability to detect yeast infections. The inhibitory effect of various lactoferrin concentrations on the growth of C. albicans in whole human milk was studied. The addition of iron to the milk led to a two- to threefold increase in cell counts when milk contained 3.0 mg of lactoferrin/ml and markedly reduced the likelihood of false-negative culture results. This method may provide the necessary objective support needed for diagnosis of mammary candidosis.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Mistrangelo, Massimiliano, E-mail: mistrangelo@katamail.co; Centre of Minimally Invasive Surgery, University of Turin; Pelosi, Ettore
2010-05-01
Background: Inguinal lymph node metastases in patients with anal cancer are an independent prognostic factor for local failure and overall mortality. Inguinal lymph node status can be adequately assessed with sentinel node biopsy, and the radiotherapy strategy can subsequently be changed. We compared this technique vs. dedicated 18F-fluorodeoxyglucose positron emission tomography (PET) to determine which was the better tool for staging inguinal lymph nodes. Methods and Materials: In our department, 27 patients (9 men and 18 women) underwent both inguinal sentinel node biopsy and PET-CT. PET-CT was performed before treatment and then at 1 and 3 months after treatment. Results:more » PET-CT scans detected no inguinal metastases in 20 of 27 patients and metastases in the remaining 7. Histologic analysis of the sentinel lymph node detected metastases in only three patients (four PET-CT false positives). HIV status was not found to influence the results. None of the patients negative at sentinel node biopsy developed metastases during the follow-up period. PET-CT had a sensitivity of 100%, with a negative predictive value of 100%. Owing to the high number of false positives, PET-CT specificity was 83%, and positive predictive value was 43%. Conclusions: In this series of patients with anal cancer, inguinal sentinel node biopsy was superior to PET-CT for staging inguinal lymph nodes.« less
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A solid-phase assay for the detection of anti-sperm antibodies.
Okada, H; Kamidono, S; Owens, G R; Nagamatsu, G R; Addonizio, J C
1993-05-01
ELISA is an ideal assay method for a large-scale screening of anti-sperm antibodies among a large number of infertile males. However, conventional ELISA with whole spermatozoa needs time-consuming steps of centrifugation. A solid-phase assay used for detecting anti-sperm antibodies was established. This assay is suitable not only for detecting circulating anti-sperm antibodies of IgG, IgM, and IgA subclass simultaneously but also for screening hybridomas secreting anti-sperm monoclonal antibodies (mAbs). The microtiter plates, on which solubilized sperm antigens are fixed, can be stored at -80 degrees C for up to six months without losing reactivity with anti-sperm antibodies. Using this assay, 53 sera (13 were proven positive and 40 were proven negative for sperm agglutination antibody) were tested. Although the false-negative rate was 0%, the false-positive rate was 32%. One thousand one hundred sixty-five supernatants from hybridomas constructed with splenocytes of mice who were hyperimmunized with human sperm and nonsecreting myeloma cells were tested by this solid-phase assay and two anti-sperm mAb secreting clones were selected and established. It is recommended that for research work this assay could be used for the first screening of the hybridoma secreting anti-sperm mAb, and for clinical use this assay might be suitable for the first screening of sera of infertile patients. However, conventional bioassays should follow to confirm the biological meaning of the positivity.
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Prieto García, M A; Delgado Sevillano, R; Baldó Sierra, C; González Díaz, E; López Secades, A; Llavona Amor, J A; Vidal Marín, B
2013-09-01
To review and classify the interval cancers found in the Principality of Asturias's Breast Cancer Screening Program (PDPCM). A secondary objective was to determine the histological characteristics, size, and stage of the interval cancers at the time of diagnosis. We included the interval cancers in the PDPCM in the period 2003-2007. Interval cancers were classified according to the breast cancer screening program protocol, with double reading without consensus, without blinding, with arbitration. Mammograms were interpreted by 10 radiologists in the PDPCM. A total of 33.7% of the interval cancers could not be classified; of the interval cancers that could be classified, 40.67% were labeled true interval cancers, 31.4% were labeled false negatives on screening, 23.7% had minimal signs, and 4.23% were considered occult. A total of 70% of the interval cancers were diagnosed in the year of the period between screening examinations and 71.7% were diagnosed after subsequent screening. A total of 76.9% were invasive ductal carcinomas, 61.1% were stage II when detected, and 78.7% were larger than 10mm when detected. The rate of interval cancers and the rate of false negatives in the PDPCM are higher than those recommended in the European guidelines. Interval cancers are diagnosed later than the tumors detected at screening. Studying interval cancers provides significant training for the radiologists in the PDPCM. Copyright © 2011 SERAM. Published by Elsevier Espana. All rights reserved.
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Conway, Damian P; Holt, Martin; McNulty, Anna; Couldwell, Deborah L; Smith, Don E; Davies, Stephen C; Cunningham, Philip; Keen, Phillip; Guy, Rebecca
2014-01-01
Determine HIV Combo (DHC) is the first point of care assay designed to increase sensitivity in early infection by detecting both HIV antibody and antigen. We conducted a large multi-centre evaluation of DHC performance in Sydney sexual health clinics. We compared DHC performance (overall, by test component and in early infection) with conventional laboratory HIV serology (fourth generation screening immunoassay, supplementary HIV antibody, p24 antigen and Western blot tests) when testing gay and bisexual men attending four clinic sites. Early infection was defined as either acute or recent HIV infection acquired within the last six months. Of 3,190 evaluation specimens, 39 were confirmed as HIV-positive (12 with early infection) and 3,133 were HIV-negative by reference testing. DHC sensitivity was 87.2% overall and 94.4% and 0% for the antibody and antigen components, respectively. Sensitivity in early infection was 66.7% (all DHC antibody reactive) and the DHC antigen component detected none of nine HIV p24 antigen positive specimens. Median HIV RNA was higher in false negative than true positive cases (238,025 vs. 37,591 copies/ml; p = 0.022). Specificity overall was 99.4% with the antigen component contributing to 33% of false positives. The DHC antibody component detected two thirds of those with early infection, while the DHC antigen component did not enhance performance during point of care HIV testing in a high risk clinic-based population.
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NASA Astrophysics Data System (ADS)
Devipriya, K.; Ivy, B. Persis Urbana; Prabha, D.
2018-04-01
A mobile ad hoc network (MANET) is an assemblage of nodes composed of mobile devices coupled in various ways wirelessly which do not have any central administration. Each node in MANET cooperates in forwarding packets in the network. This type of collaboration incurs high cost but there exits nodes that declines to cooperate leading to selfish conduct of nodes which effects overall network performance. To discover the attacks caused by such nodes, a renowned mechanism using watchdog can be deployed. In infrastructure less network attack detection and reaction and high false positives, false negatives initiating black hole attack becomes major issue in watchdog. This paper put forward a collaborative approach for identifying such attacks in MANET. Through abstract analysis and extensive simulation of this approach, the detection time of misbehaved nodes is reduced and substantial enhancement in overhead and throughput is witnessed.
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Optical detection of chemical warfare agents and toxic industrial chemicals
NASA Astrophysics Data System (ADS)
Webber, Michael E.; Pushkarsky, Michael B.; Patel, C. Kumar N.
2004-12-01
We present an analytical model evaluating the suitability of optical absorption based spectroscopic techniques for detection of chemical warfare agents (CWAs) and toxic industrial chemicals (TICs) in ambient air. The sensor performance is modeled by simulating absorption spectra of a sample containing both the target and multitude of interfering species as well as an appropriate stochastic noise and determining the target concentrations from the simulated spectra via a least square fit (LSF) algorithm. The distribution of the LSF target concentrations determines the sensor sensitivity, probability of false positives (PFP) and probability of false negatives (PFN). The model was applied to CO2 laser based photoacosutic (L-PAS) CWA sensor and predicted single digit ppb sensitivity with very low PFP rates in the presence of significant amount of interferences. This approach will be useful for assessing sensor performance by developers and users alike; it also provides methodology for inter-comparison of different sensing technologies.
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Chemiluminescent DNA optical fibre sensor for Brettanomyces bruxellensis detection.
Cecchini, Francesca; Manzano, Marisa; Mandabi, Yohai; Perelman, Eddie; Marks, Robert S
2012-01-01
Food and beverage industries require rapid tests to limit economic losses and one way to do so is via molecular tests. In the present work, DNA capture and secondary probes, were designed to target the ITS (Internal Transcribed) sequences of Brettanomyces bruxellensis, a yeast responsible for the production of off flavours in both wine and beer. ITS1 and ITS2 were found to contain distinct regions with sufficient sequence divergence to make them suitable as specific identification target sites. The dot blot technique was used to determine the sensitivity and specificity of the capture probe. Both probes were, thereafter, adapted to construct an optical fibre genosensor, which produced neither false positives nor false negatives, and was both repeatable and faster with respect to traditional methods, the latter requiring at least one week to detect B. bruxellensis. Copyright © 2011 Elsevier B.V. All rights reserved.
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SPEPlip: the detection of signal peptide and lipoprotein cleavage sites.
Fariselli, Piero; Finocchiaro, Giacomo; Casadio, Rita
2003-12-12
SPEPlip is a neural network-based method, trained and tested on a set of experimentally derived signal peptides from eukaryotes and prokaryotes. SPEPlip identifies the presence of sorting signals and predicts their cleavage sites. The accuracy in cross-validation is similar to that of other available programs: the rate of false positives is 4 and 6%, for prokaryotes and eukaryotes respectively and that of false negatives is 3% in both cases. When a set of 409 prokaryotic lipoproteins is predicted, SPEPlip predicts 97% of the chains in the signal peptide class. However, by integrating SPEPlip with a regular expression search utility based on the PROSITE pattern, we can successfully discriminate signal peptide-containing chains from lipoproteins. We propose the method for detecting and discriminating signal peptides containing chains and lipoproteins. It can be accessed through the web page at http://gpcr.biocomp.unibo.it/predictors/
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Simulation study into the identification of nuclear materials in cargo containers using cosmic rays
NASA Astrophysics Data System (ADS)
Blackwell, T. B.; Kudryavtsev, V. A.
2015-04-01
Muon tomography represents a new type of imaging technique that can be used in detecting high-Z materials. Monte Carlo simulations for muon scattering in different types of target materials are presented. The dependence of the detector capability to identify high-Z targets on spatial resolution has been studied. Muon tracks are reconstructed using a basic point of closest approach (PoCA) algorithm. In this article we report the development of a secondary analysis algorithm that is applied to the reconstructed PoCA points. This algorithm efficiently ascertains clusters of voxels with high average scattering angles to identify `areas of interest' within the inspected volume. Using this approach the effect of other parameters, such as the distance between detectors and the number of detectors per set, on material identification is also presented. Finally, false positive and false negative rates for detecting shielded HEU in realistic scenarios with low-Z clutter are presented.
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Tirnaksiz, M B; Deschamps, C; Allen, M S; Johnson, D C; Pairolero, P C
2005-01-01
Aqueous contrast swallow study is recommended as a screening procedure for the evaluation of esophageal anastomotic integrity following esophagectomy. The aim of this study was to assess the accuracy of water-soluble contrast swallow screening as a predictor of clinically significant anastomotic leak in patients with esophagectomy. The records of 505 consecutive patients undergoing esophagectomy in Mayo Clinic from January 1991 through December 1995 were retrospectively reviewed. 464 (92%) patients had water-soluble contrast swallows performed in the early postoperative period (median postoperative day 7, range 4-11 days). A total of 39 radiological leaks were obtained but only 17 of these had clinical signs of anastomotic leakage. Furthermore, 25 patients who had normal swallow study developed a clinical anastomotic leak. There were therefore 22 (4.7%) false positive and 25 (5.4%) false negative results giving values for the specificity, sensitivity and false negative error rate of the radiological examination of 94.7, 40.4, and 59.5% respectively. Aspiration of the contrast agent was noted on fluoroscopy in 30 (6.5%) patients. Only 2 (0.4%) patients developed aqueous contrast agent-caused aspiration pneumonia. There was no procedure-related mortality. While radiological assessment of esophageal anastomoses in the early postoperative period using aqueous contrast agents appears to be a relatively safe procedure, the poor sensitivity and high false negative error rate of this technique, when performed on postoperative day 7 and in a series with clinical anastomotic leak rate of 9%, is insufficient for it to be worthwhile as a screening procedure. Copyright (c) 2005 S. Karger AG, Basel.
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Hoffmann, Manuela A; Miederer, Matthias; Wieler, Helmut J; Ruf, Christian; Jakobs, Frank M; Schreckenberger, Mathias
2017-12-19
Radiolabeled prostate-specific membrane antigen (PSMA) has proven to be a highly accurate method to detect recurrence and metastases of prostate cancer, but only sparse data is available about its performance in the diagnosis of clinically significant primary prostate cancer. We compared 68 Ga-PSMA-11 PET/CT in 25 patients with 18 FEC PET/CT in 40 patients with suspected prostate carcinoma based on an increased PSA level.The PET/CT results were compared with the histopathologic Gleason Score (GS) of biopsies. The 68 Ga-PSMA-11 PET/CT revealed highly suspect prostatic lesions (maximum standardized uptake value/SUV max >2.5) in 21/25 patients (84%), associated with GS≥6 (low-grade/high-grade carcinoma). Two histopathologic non-malignancy-relevant cases (GS<6) had PSMA-SUV max ≤2.5; all histopathologic high-grade cases (GS≥7b) showed PSMA-SUV max >12.0 which further increased with rising GS. There were 2 false positives and no false negative findings for high-grade prostate cancer using a cut off-level for SUV max of 2.5.In contrast, the 18 FEC PET/CT showed suspected malignant lesions in 38/40 patients (95%), which included 3 lesions with GS<6. The mean SUV max values did not differ with different GS. There were 11 false positives and 1 false negative for detection of high-grade prostate cancer (cut off 2.5).By means of ROC analysis a SUV max of 5.4 was found to be an optimal cut off-level to distinguish between low- and high-grade carcinoma in 68 Ga-PSMA-11 PET/CT (AUC=0.9692; 95% CI 0.9086;1.0000;SD(AUC)=0.0309)). Choosing a cut off-level of SUV max 5.4, 68 Ga-PSMA-11 PET/CT was able to distinguish between GS ≤7a/≥7b with a sensitivity of 84%, a specificity of 100%, a negative predictive value (NPV) of 67%, and an efficiency of 88% ( p <0.001).The ROC analysis revealed a SUV max 6.5 as an optimal cut off-level to distinguish between low- and high-grade carcinoma in 18 FEC PET/CT (AUC=0.7470; 95% CI 0.5919;0.9020;SD(AUC)=0.0791) with a sensitivity of 61% and a specificity of 92%; but the efficiency was only 70% and the NPV 50% ( p =0.01). 68 Ga-PSMA-11 PET/CT guided biopsy of the prostate increases diagnostic precision and is likely to help to reduce overtreatment of low-grade malignant disease as well as detect the foci of the highest Gleason pattern. Both methods ( 68 Ga-PSMA-11, 18 FEC) were suitable to detect primary prostate cancer, but the excellent image quality, the higher specificity and the good correlation of positive scans with GS are advantages of 68 Ga-PSMA-11.
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Dunford, Linda; Freitas, Ines; Holder, Paul; Nguyen, Lan Anh; O'Gorman, Joanne; Connell, Jeff; Carr, Michael; Hall, William; De Gascun, Cillian
2015-01-01
Genetic characterization of the genotype 3a (GT3a) hepatitis C virus (HCV) core region from HCV core antigen (HCVcAg)-negative/RNA-positive cases and HCVcAg-positive/RNA-positive controls identified significant associations between the substitutions A48T and T49A/P and failure to detect HCVcAg (P < 0.05). Polymorphisms at residues 48 and 49 in the core protein are present across all major epidemic and endemic GTs. These findings have implications for HCV diagnosis, particularly in low-income regions in which GT3a HCV is endemic. PMID:25994168
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Rapid response radiation sensors for homeland security applications
NASA Astrophysics Data System (ADS)
Mukhopadhyay, Sanjoy; Maurer, Richard; Guss, Paul
2014-09-01
The National Security Technologies, LLC, Remote Sensing Laboratory is developing a rapid response radiation detection system for homeland security field applications. The intelligence-driven system is deployed only when non-radiological information about the target is verifiable. The survey area is often limited, so the detection range is small; in most cases covering a distance of 10 meters or less suffices. Definitive response is required in no more than 3 seconds and should minimize false negative alarms, but can err on the side of positive false alarms. The detection system is rapidly reconfigurable in terms of size, shape, and outer appearance; it is a plug-and-play system. Multiple radiation detection components (viz., two or more sodium iodide scintillators) are used to independently "over-determine" the existence of the threat object. Rapid response electronic dose rate meters are also included in the equipment suite. Carefully studied threat signatures are the basis of the decision making. The use of Rad-Detect predictive modeling provides information on the nature of the threat object. Rad-Detect provides accurate dose rate from heavily shielded large sources; for example those lost in Mexico were Category 1 radiation sources (~3,000 Ci of 60Co), the most dangerous of five categories defined by the International Atomic Energy Agency. Taken out of their shielding containers, Category 1 sources can kill anyone who is exposed to them at close range for a few minutes to an hour. Whenever possible sub-second data acquisition will be attempted, and, when deployed, the system will be characterized for false alarm rates. Although the radiation detection materials selected are fast (viz., faster scintillators), their speed is secondary to sensitivity, which is of primary importance. Results from these efforts will be discussed and demonstrated.
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Pre-Participation Musculoskeletal and Cardiac Screening of Male Athletes in the United Arab Emirates
Alattar, A; Ghani, S; Mahdy, N; Hussain, H; Maffulli, N
2014-01-01
This study presents the results of pre-participation musculoskeletal and cardiac screening using the Lausanne recommendations, which include a personal and family history, physical examination and electrocardiography. Cross sectional study using the Lausanne screenings and the European Society of Cardiology (ESC) recommendations carried out at Al-Ahli club in Dubai, United Arab Emirates. 230 male athletes participating in organised sports were included. Exclusion criteria were those under 14 or over 35 years old, females and athletes with established cardiovascular disease. Primary outcome are the results of Lausanne screening with outline of the negative, positive and false positive results and number needed to screen. Secondary outcomes include the results of musculoskeletal and neurological screening. A total of 174 (76%) athletes had a negative screening result. Fifty-four athletes (23%) underwent additional testing. Forty-seven athletes (20.4%) had false positive screening results. Seven athletes (3%) had a positive screening result and four athletes (2%) were restricted from sport. The number of athletes needed to screen to detect one lethal cardiovascular condition was 33 athletes. The Lausanne recommendations are well suited for the United Arab Emirates. The number needed to screen to detect one athlete with serious cardiovascular disease is acceptable at 33. PMID:24809035
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A new approach for low-cost noninvasive detection of asymptomatic heart disease at rest.
DeMarzo, Arthur P; Calvin, James E
2007-01-01
It would be useful to have an inexpensive, noninvasive point-of-care test for early detection of asymptomatic heart disease. This study used impedance cardiography (ICG) in a new way to assess heart function that did not use stroke volume or cardiac output. There is a model of the ICG dZ/dt waveform that may be used as a template to represent normal heart function. The hypothesis was that a dZ/dt waveform which deviates from that template should indicate heart dysfunction and therefore heart disease. The objective was to assess the accuracy of this new ICG approach, using echocardiography as the standard. Thirty-four outpatients undergoing echocardiographic testing were tested by ICG while sitting upright and supine. All patients had no symptoms or history of a structural or functional heart disorder. Echocardiographic testing showed 17 patients with abnormalities and 17 as normal. ICG testing yielded 16 true positives for heart dysfunction with 1 false negative (sensitivity = 94%) and 17 true negatives with no false positives (specificity = 100%). Considering that the cost, technical skill, and time required for this ICG test are comparable to those of an electrocardiograph, this new approach has potential as a point-of-care screening test for asymptomatic heart disease.
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New monoclonal antibody-based test for Helicobacter pylori urease in gastric tissue.
Kim, Do Hyun; Kim, Ho Dong; Park, Hyeuk; Choi, Seung; Beom, Jae Won; Kim, Woo Jong; Park, Chang Kook; Lee, Young Jik; Park, Ju Young; Kim, Hyung Rag; Park, Chul; Joo, Young Eun; Jung, Young Do
2016-01-01
To evaluate a new monoclonal antibody for Helicobacter pylori urease in gastric tissue. A total of 107 volunteers were enrolled. All subjects underwent a (13)C-urea breath test and esophagogastroduodenoscopy. Gastric aspirates were analyzed for pH and ammonia. Six biopsy specimens in the gastric antrum and body were obtained for a rapid urease test and histology. The new monoclonal antibody-based H. pylori urease test (HPU) was performed to rapidly and qualitatively detect urease in two biopsy specimens. H. pylori infection was diagnosed in 73 subjects. The sensitivity and specificity of the HPU was 89% and 74%, respectively. The subjects were divided into two groups: one with true-positive and true-negative HPU results (n = 90) and the other with false-positive and false-negative HPU results (n = 17). Across all subjects, ammonia levels were 900.5 ± 646.7 and 604.3 ± 594.3 μmol/L (p > 0.05), and pH was 3.37 ± 1.64 and 2.82 ± 1.51 (p > 0.05). Sensitivity was higher in the presence of atrophic gastritis or intestinal metaplasia. HPU detected H. pylori in approximately 10 min. Gastric aspirate ammonia and pH levels did not affect the test results. Sensitivity was good in the presence of atrophic gastritis or intestinal metaplasia.
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Mapping of Synaptic-Neuronal Impairment on the Brain Surface through Fluctuation Analysis
DOE Office of Scientific and Technical Information (OSTI.GOV)
Musha, Toshimitsu; Kurachi, Takayoshi; Suzuki, Naohoro
2005-08-25
Increase of demented population year by year is becoming a serious social problem to be solved urgently. The most effective way to block this increase is in its early detection by means of an inexpensive, non-invasive, sensitive, reliable and easy-to-operate diagnosis method. We have developed a method satisfying these requirements by using scalp potential fluctuations. We have collected 21ch EEG and SPECT data of 25 very mild Alzheimer's disease (AD) (MMSE=26{+-}1.8), moderately severe AD (MMSE=15.3{+-}6.4) and age-matched normal controls. As AD progresses, local synaptic-neuronal activity becomes abnormal, either more unstable or more inactive than in normal state. Such abnormality ismore » detected in terms of normalized power variance (NPV) of a scalp potential recorded with a scalp electrode. The z-score is defined by z = ((NPV of a subject) - (mean NPV of normal subjects))/(standard deviation of NPV of normal subjects). Correlation of a measured z-score map with the mean z-score map for AD patients characterizes likelihood to AD, in terms of which AD is discriminated from normal with 75% of true positive and 25% false negative probability. By introducing two thresholds, we have 90% of true positive and 10% of false negative discrimination.« less
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García-Hoyos, María; Cortón, Marta; Ávila-Fernández, Almudena; Riveiro-Álvarez, Rosa; Giménez, Ascensión; Hernan, Inma; Carballo, Miguel; Ayuso, Carmen
2012-01-01
Purpose Presently, 22 genes have been described in association with autosomal dominant retinitis pigmentosa (adRP); however, they explain only 50% of all cases, making genetic diagnosis of this disease difficult and costly. The aim of this study was to evaluate a specific genotyping microarray for its application to the molecular diagnosis of adRP in Spanish patients. Methods We analyzed 139 unrelated Spanish families with adRP. Samples were studied by using a genotyping microarray (adRP). All mutations found were further confirmed with automatic sequencing. Rhodopsin (RHO) sequencing was performed in all negative samples for the genotyping microarray. Results The adRP genotyping microarray detected the mutation associated with the disease in 20 of the 139 families with adRP. As in other populations, RHO was found to be the most frequently mutated gene in these families (7.9% of the microarray genotyped families). The rate of false positives (microarray results not confirmed with sequencing) and false negatives (mutations in RHO detected with sequencing but not with the genotyping microarray) were established, and high levels of analytical sensitivity (95%) and specificity (100%) were found. Diagnostic accuracy was 15.1%. Conclusions The adRP genotyping microarray is a quick, cost-efficient first step in the molecular diagnosis of Spanish patients with adRP. PMID:22736939
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Clinical outcome of subchromosomal events detected by whole‐genome noninvasive prenatal testing
Helgeson, J.; Wardrop, J.; Boomer, T.; Almasri, E.; Paxton, W. B.; Saldivar, J. S.; Dharajiya, N.; Monroe, T. J.; Farkas, D. H.; Grosu, D. S.
2015-01-01
Abstract Objective A novel algorithm to identify fetal microdeletion events in maternal plasma has been developed and used in clinical laboratory‐based noninvasive prenatal testing. We used this approach to identify the subchromosomal events 5pdel, 22q11del, 15qdel, 1p36del, 4pdel, 11qdel, and 8qdel in routine testing. We describe the clinical outcomes of those samples identified with these subchromosomal events. Methods Blood samples from high‐risk pregnant women submitted for noninvasive prenatal testing were analyzed using low coverage whole genome massively parallel sequencing. Sequencing data were analyzed using a novel algorithm to detect trisomies and microdeletions. Results In testing 175 393 samples, 55 subchromosomal deletions were reported. The overall positive predictive value for each subchromosomal aberration ranged from 60% to 100% for cases with diagnostic and clinical follow‐up information. The total false positive rate was 0.0017% for confirmed false positives results; false negative rate and sensitivity were not conclusively determined. Conclusion Noninvasive testing can be expanded into the detection of subchromosomal copy number variations, while maintaining overall high test specificity. In the current setting, our results demonstrate high positive predictive values for testing of rare subchromosomal deletions. © 2015 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd. PMID:26088833
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Peeters, Dominique; Peters, Iain R; Helps, Chris R; Dehard, Sandrine; Day, Michael J; Clercx, Cécile
2008-04-01
Various combinations of tests are used to confirm the diagnosis of canine sino-nasal aspergillosis (SNA) because false-positive and false-negative results can occur with each test. Therefore, the aim of this study was to evaluate whether detection of fungal DNA in blood and nasal tissue samples was of value in the clinical diagnosis of this disease. Four groups were included in the study (dogs with SNA, lymphoplasmacytic rhinitis or nasal neoplasia, and control animals). Real-time PCR assays detecting DNA from all Penicillium and Aspergillus species (PenAsp assay) or species-specific DNA from A. fumigatus, A. terreus, A. flavus and A. niger were applied to whole blood and nasal tissue samples. Results obtained by PCR were compared between the groups. Sensitivity, specificity, positive and negative predictive values (PPV and NPV) for fungal DNA detection were compared with those for alternative diagnostic procedures including histopathology, serology and fungal culture. Significantly more fungal DNA was detected by the PenAsp assay in tissue biopsies from dogs with SNA than in the three other groups. Sensitivity, specificity, PPV and NPV for this method were 1.00, 0.06, 0.32 and 1.00. A. fumigatus DNA was detected in seven tissue biopsies from dogs with SNA and in one biopsy from a dog with a nasal tumour. Sensitivity, specificity, PPV and NPV for this diagnostic test were 0.50, 0.97, 0.87 and 0.82. No significant difference was found between the groups with respect to the amount of DNA detected in blood by the PenAsp assay. Sensitivity, specificity, PPV and NPV for this method were 0.71, 0.24, 0.31 and 0.64. A. fumigatus DNA was detected in the blood of three dogs with SNA and sixteen dogs without SNA. Sensitivity, specificity, PPV and NPV for this diagnostic tool were 0.21, 0.45, 0.15 and 0.54. Detection of A. fumigatus DNA in nasal tissue had the highest specificity, PPV and NPV but sensitivity of this method was low. Detection of fungal DNA in whole blood was of no value in the diagnosis of SNA.
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Rahimi-Movaghar, Vafa; Yousefifard, Mahmoud; Ghelichkhani, Parisa; Baikpour, Masoud; Tafakhori, Abbas; Asady, Hadi; Faridaalaee, Gholamreza; Hosseini, Mostafa; Safari, Saeed
2016-01-01
Hemothorax is one of the most prevalent injuries caused by thoracic traumas. Early detection and treatment of this injury is of utmost importance in prognosis of the patient, but there are still controversial debates on the diagnostic value of imaging techniques in detection of hemothorax. Therefore, the present study aimed to evaluate the diagnostic value of chest ultrasonography and radiography in detection of hemothorax through a systematic review and meta-analysis. Two independent reviewers performed an extended systematic search in databases of Medline, EMBASE, ISI Web of Knowledge, Scopus, Cochrane Library, and ProQuest. Data were extract and quality of the relevant studies were assessed. The number of true positive, false positive, true negative and false negative cases were extracted and screening performance characteristics of two imaging techniques were calculated using a mixed-effects binary regression model. Data from 12 studies were extracted and included in the meta-analysis (7361 patients, 77.1% male). Pooled sensitivity and specificity of ultrasonography in detection of hemothorax were 0.67 (95% CI: 0.41-0.86; I2= 68.38, p<0.001) and 0.99 (95% CI: 0.95-1.0; I2= 88.16, p<0.001), respectively. These measures for radiography were 0.54 (95% CI: 0.33-0.75; I2= 92.85, p<0.001) and 0.99 (95% CI: 0.94-1.0; I2= 99.22, p<0.001), respectively. Subgroup analysis found operator of the ultrasonography device, frequency of the transducer and sample size to be important sources of heterogeneity of included studies. The results of this study showed that although the sensitivity of ultrasonography in detection of hemothorax is relatively higher than radiography, but it is still at a moderate level (0.67%). The specificity of both imaging modalities were found to be at an excellent level in this regard. The screening characteristics of ultrasonography was found to be influenced of the operator and frequency of transducer.
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Yousefifard, Mahmoud; Baikpour, Masoud; Ghelichkhani, Parisa; Asady, Hadi; Darafarin, Abolfazl; Amini Esfahani, Mohammad Reza; Hosseini, Mostafa; Yaseri, Mehdi; Safari, Saeed
2016-01-01
Introduction: The potential benefit of ultrasonography for detection of thoracic bone fractures has been proven in various surveys but no comprehensive conclusion has been drawn yet; therefore, the present study aimed to conduct a thorough meta-analytic systematic review on this subject. Methods: Two reviewers independently carried out a comprehensive systematic search in Medline, EMBASE, ISI Web of Knowledge, Scopus, Cochrane Library, and ProQuest databases. Data were summarized as true positive, false positive, true negative and false negative and were analyzed via STATA 11.0 software using a mixed-effects binary regression model. Sources of heterogeneity were further assessed through subgroup analysis. Results: Data on 1667 patients (807 subjects with and 860 cases without thoracic fractures), whose age ranged from 0 to 92 years, were extracted from 17 surveys. Pooled sensitivity and specificity of ultrasonography in detection of thoracic bone fractures were 0.97 (95% CI: 0.90-0.99; I2= 88.88, p<0.001) and 0.94 (95% CI: 0.86-0.97; I2= 71.97, p<0.001), respectively. The same measures for chest radiography were found to be 0.77 (95% CI: 0.56-0.90; I2= 97.76, p<0.001) and 1.0 (95% CI: 0.91-1.00; I2= 97.24, p<0.001), respectively. The sensitivity of ultrasonography was higher in detection of rib fractures, compared to fractures of sternum or clavicle (97% vs. 91%). Moreover, the sensitivity was found to be higher when the procedure was carried out by a radiologist in comparison to an emergency medicine specialist (96% vs. 90%). Conclusion: Base on the findings of the present meta-analysis, screening performance characteristic of ultrasonography in detection of thoracic bone fractures was found to be higher than radiography. However, these characteristics were more prominent in detection of rib fractures and in cases where was performed by a radiologist. PMID:27274514
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Yousefifard, Mahmoud; Baikpour, Masoud; Ghelichkhani, Parisa; Asady, Hadi; Darafarin, Abolfazl; Amini Esfahani, Mohammad Reza; Hosseini, Mostafa; Yaseri, Mehdi; Safari, Saeed
2016-01-01
The potential benefit of ultrasonography for detection of thoracic bone fractures has been proven in various surveys but no comprehensive conclusion has been drawn yet; therefore, the present study aimed to conduct a thorough meta-analytic systematic review on this subject. Two reviewers independently carried out a comprehensive systematic search in Medline, EMBASE, ISI Web of Knowledge, Scopus, Cochrane Library, and ProQuest databases. Data were summarized as true positive, false positive, true negative and false negative and were analyzed via STATA 11.0 software using a mixed-effects binary regression model. Sources of heterogeneity were further assessed through subgroup analysis. Data on 1667 patients (807 subjects with and 860 cases without thoracic fractures), whose age ranged from 0 to 92 years, were extracted from 17 surveys. Pooled sensitivity and specificity of ultrasonography in detection of thoracic bone fractures were 0.97 (95% CI: 0.90-0.99; I2= 88.88, p<0.001) and 0.94 (95% CI: 0.86-0.97; I2= 71.97, p<0.001), respectively. The same measures for chest radiography were found to be 0.77 (95% CI: 0.56-0.90; I2= 97.76, p<0.001) and 1.0 (95% CI: 0.91-1.00; I2= 97.24, p<0.001), respectively. The sensitivity of ultrasonography was higher in detection of rib fractures, compared to fractures of sternum or clavicle (97% vs. 91%). Moreover, the sensitivity was found to be higher when the procedure was carried out by a radiologist in comparison to an emergency medicine specialist (96% vs. 90%). Base on the findings of the present meta-analysis, screening performance characteristic of ultrasonography in detection of thoracic bone fractures was found to be higher than radiography. However, these characteristics were more prominent in detection of rib fractures and in cases where was performed by a radiologist.
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Evaluating 6 ricin field detection assays.
Slotved, Hans-Christian; Sparding, Nadja; Tanassi, Julia Tanas; Steenhard, Nina R; Heegaard, Niels H H
2014-01-01
This study presents data showing the performance of 6 commercial detection assays against ricin around concentrations specified as detection limits by the producers. A 2-fold dilution series of 20 ng/ml ricin was prepared and used for testing the lateral-flow kits: BADD, Pro Strips™, ENVI, RAID DX, Ricin BioThreat Alert, and IMASS™ device. Three of the 6 tested field assays (IMASS™ device, ENVI assay, and the BioThreat Alert assay) were able to detect ricin, although differences in the measured detection limits compared to the official detection limits and false-negative results were observed. We were not able to get the BADD, Pro Strips™, and RAID assays to function in our laboratory. We conclude that when purchasing a field responder assay, there is large variation in the specificity of the assays, and a number of in-house tests must be performed to ensure functionality.
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Unsupervised Ensemble Anomaly Detection Using Time-Periodic Packet Sampling
NASA Astrophysics Data System (ADS)
Uchida, Masato; Nawata, Shuichi; Gu, Yu; Tsuru, Masato; Oie, Yuji
We propose an anomaly detection method for finding patterns in network traffic that do not conform to legitimate (i.e., normal) behavior. The proposed method trains a baseline model describing the normal behavior of network traffic without using manually labeled traffic data. The trained baseline model is used as the basis for comparison with the audit network traffic. This anomaly detection works in an unsupervised manner through the use of time-periodic packet sampling, which is used in a manner that differs from its intended purpose — the lossy nature of packet sampling is used to extract normal packets from the unlabeled original traffic data. Evaluation using actual traffic traces showed that the proposed method has false positive and false negative rates in the detection of anomalies regarding TCP SYN packets comparable to those of a conventional method that uses manually labeled traffic data to train the baseline model. Performance variation due to the probabilistic nature of sampled traffic data is mitigated by using ensemble anomaly detection that collectively exploits multiple baseline models in parallel. Alarm sensitivity is adjusted for the intended use by using maximum- and minimum-based anomaly detection that effectively take advantage of the performance variations among the multiple baseline models. Testing using actual traffic traces showed that the proposed anomaly detection method performs as well as one using manually labeled traffic data and better than one using randomly sampled (unlabeled) traffic data.
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Proof of Concept of Automated Collision Detection Technology in Rugby Sevens.
Clarke, Anthea C; Anson, Judith M; Pyne, David B
2017-04-01
Clarke, AC, Anson, JM, and Pyne, DB. Proof of concept of automated collision detection technology in rugby sevens. J Strength Cond Res 31(4): 1116-1120, 2017-Developments in microsensor technology allow for automated detection of collisions in various codes of football, removing the need for time-consuming postprocessing of video footage. However, little research is available on the ability of microsensor technology to be used across various sports or genders. Game video footage was matched with microsensor-detected collisions (GPSports) in one men's (n = 12 players) and one women's (n = 12) rugby sevens match. True-positive, false-positive, and false-negative events between video and microsensor-detected collisions were used to calculate recall (ability to detect a collision) and precision (accurately identify a collision). The precision was similar between the men's and women's rugby sevens game (∼0.72; scale 0.00-1.00); however, the recall in the women's game (0.45) was less than that for the men's game (0.69). This resulted in 45% of collisions for men and 62% of collisions for women being incorrectly labeled. Currently, the automated collision detection system in GPSports microtechnology units has only modest utility in rugby sevens, and it seems that a rugby sevens-specific algorithm is needed. Differences in measures between the men's and women's game may be a result of physical size, and strength, and physicality, as well as technical and tactical factors.
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Gliner, Vadim; Behar, Joachim; Yaniv, Yael
2018-05-22
In parallel to the introduction of mobile communication devices with high computational power and internet connectivity, high-quality and low-cost health sensors have also become available. However, although the technology does exist, no clinical mobile system has been developed to monitor the R peaks from electrocardiogram recordings in real time with low false positive and low false negative detection. Implementation of a robust electrocardiogram R peak detector for various arrhythmogenic events has been hampered by the lack of an efficient design that will conserve battery power without reducing algorithm complexity or ease of implementation. Our goals in this paper are (1) to evaluate the suitability of the MATLAB Mobile platform for mHealth apps and whether it can run on any phone system, and (2) to embed in the MATLAB Mobile platform a real-time electrocardiogram R peak detector with low false positive and low false negative detection in the presence of the most frequent arrhythmia, atrial fibrillation. We implemented an innovative R peak detection algorithm that deals with motion artifacts, electrical drift, breathing oscillations, electrical spikes, and environmental noise by low-pass filtering. It also fixes the signal polarity and deals with premature beats by heuristic filtering. The algorithm was trained on the annotated non-atrial fibrillation MIT-BIH Arrhythmia Database and tested on the atrial fibrillation MIT-BIH Arrhythmia Database. Finally, the algorithm was implemented on mobile phones connected to a mobile electrocardiogram device using the MATLAB Mobile platform. Our algorithm precisely detected the R peaks with a sensitivity of 99.7% and positive prediction of 99.4%. These results are superior to some state-of-the-art algorithms. The algorithm performs similarly on atrial fibrillation and non-atrial fibrillation patient data. Using MATLAB Mobile, we ran our algorithm in less than an hour on both the iOS and Android system. Our app can accurately analyze 1 minute of real-time electrocardiogram signals in less than 1 second on a mobile phone. Accurate real-time identification of heart rate on a beat-to-beat basis in the presence of noise and atrial fibrillation events using a mobile phone is feasible. ©Vadim Gliner, Joachim Behar, Yael Yaniv. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 22.05.2018.
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Brassel, J; Rohrssen, F; Failing, K; Wehrend, A
2018-06-11
To evaluate the performance of a novel accelerometer-based oestrus detection system (ODS) for dairy cows on pasture, in comparison with measurement of concentrations of progesterone in milk, ultrasonographic examination of ovaries and farmer observations. Mixed-breed lactating dairy cows (n=109) in a commercial, seasonal-calving herd managed at pasture under typical farming conditions in Ireland, were fitted with oestrus detection collars 3 weeks prior to mating start date. The ODS performed multimetric analysis of eight different motion patterns to generate oestrus alerts. Data were collected during the artificial insemination period of 66 days, commencing on 16 April 2015. Transrectal ultrasonographic examinations of the reproductive tract and measurements of concentrations of progesterone in milk were used to confirm oestrus events. Visual observations by the farmer and the number of theoretically expected oestrus events were used to evaluate the number of false negative ODS alerts. The percentage of eligible cows that were detected in oestrus at least once (and were confirmed true positives) was calculated for the first 21, 42 and 63 days of the insemination period. During the insemination period, the ODS generated 194 oestrus alerts and 140 (72.2%) were confirmed as true positives. Six confirmed oestrus events recognised by the farmer did not generate ODS alerts. The positive predictive value of the ODS was 72.2 (95% CI=65.3-78.4)%. To account for oestrus events not identified by the ODS or the farmer, four theoretical missed oestrus events were added to the false negatives. Estimated sensitivity of the automated ODS was 93.3 (95% CI=88.1-96.8)%. The proportion of eligible cows that were detected in oestrus during the first 21 days of the insemination period was 92/106 (86.8%), and during the first 42 and 63 days of the insemination period was 103/106 (97.2%) and 105/106 (99.1%), respectively. The ODS under investigation was suitable for oestrus detection in dairy cows on pasture and showed a high sensitivity of oestrus detection. Multimetric analysis of behavioural data seems to be the superior approach to developing and improving ODS for dairy cows on pasture. Due to a high proportion of false positive alerts, its use as a stand-alone system for oestrus detection cannot be recommended. As it is the first time the system was investigated, testing on other farms would be necessary for further validation.
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Tang, Tianyu; Zhou, Shilin; Deng, Zhipeng; Zou, Huanxin; Lei, Lin
2017-02-10
Detecting vehicles in aerial imagery plays an important role in a wide range of applications. The current vehicle detection methods are mostly based on sliding-window search and handcrafted or shallow-learning-based features, having limited description capability and heavy computational costs. Recently, due to the powerful feature representations, region convolutional neural networks (CNN) based detection methods have achieved state-of-the-art performance in computer vision, especially Faster R-CNN. However, directly using it for vehicle detection in aerial images has many limitations: (1) region proposal network (RPN) in Faster R-CNN has poor performance for accurately locating small-sized vehicles, due to the relatively coarse feature maps; and (2) the classifier after RPN cannot distinguish vehicles and complex backgrounds well. In this study, an improved detection method based on Faster R-CNN is proposed in order to accomplish the two challenges mentioned above. Firstly, to improve the recall, we employ a hyper region proposal network (HRPN) to extract vehicle-like targets with a combination of hierarchical feature maps. Then, we replace the classifier after RPN by a cascade of boosted classifiers to verify the candidate regions, aiming at reducing false detection by negative example mining. We evaluate our method on the Munich vehicle dataset and the collected vehicle dataset, with improvements in accuracy and robustness compared to existing methods.
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Monaghan, S J; Thompson, K D; Adams, A; Bergmann, S M
2015-03-01
Koi herpesvirus (KHV) causes an economically important, highly infectious disease in common carp and koi, Cyprinus carpio L. Since the occurrence of mass mortalities worldwide, highly specific and sensitive molecular diagnostic methods have been developed for KHV detection. The sensitivity and reliability of these assays have essentially focused at the detection of low viral DNA copy numbers during latent or persistent infections. However, the efficacy of these assays has not been investigated with regard to low-level viraemia during acute infection stages. This study was conducted to compare the sensitivity of seven different polymerase chain reaction (PCR) assays to detect KHV during the first hours and days post-infection (hpi; dpi), using lethal and non-lethal sampling methods. The results highlight the limitations of the assays for detecting virus during the first 4 dpi despite rapid mortality in experimentally infected carp. False-negative results were associated with time post-infection and the tissue sampled. Non-lethal sampling appears effective for KHV screening, with efficient detection in mucus samples obtained from external swabs during this early infection period (<5 dpi), while biopsies from gills and kidney were negative using the same PCR assays. Non-lethal sampling may improve the reliability of KHV detection in subclinical, acutely infected carp. © 2014 John Wiley & Sons Ltd.
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Plasmodium vivax molecular diagnostics in community surveys: pitfalls and solutions.
Gruenberg, Maria; Moniz, Clara Antunes; Hofmann, Natalie Ellen; Wampfler, Rahel; Koepfli, Cristian; Mueller, Ivo; Monteiro, Wuelton Marcelo; Lacerda, Marcus; de Melo, Gisely Cardoso; Kuehn, Andrea; Siqueira, Andre M; Felger, Ingrid
2018-01-30
A distinctive feature of Plasmodium vivax infections is the overall low parasite density in peripheral blood. Thus, identifying asymptomatic infected individuals in endemic communities requires diagnostic tests with high sensitivity. The detection limits of molecular diagnostic tests are primarily defined by the volume of blood analysed and by the copy number of the amplified molecular marker serving as the template for amplification. By using mitochondrial DNA as the multi-copy template, the detection limit can be improved more than tenfold, compared to standard 18S rRNA targets, thereby allowing detection of lower parasite densities. In a very low transmission area in Brazil, application of a mitochondrial DNA-based assay increased prevalence from 4.9 to 6.5%. The usefulness of molecular tests in malaria epidemiological studies is widely recognized, especially when precise prevalence rates are desired. Of concern, however, is the challenge of demonstrating test accuracy and quality control for samples with very low parasite densities. In this case, chance effects in template distribution around the detection limit constrain reproducibility. Rigorous assessment of false positive and false negative test results is, therefore, required to prevent over- or under-estimation of parasite prevalence in epidemiological studies or when monitoring interventions.
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Arjona, Alvaro; Barquero, Nuria; Doménech, Ana; Tejerizo, German; Collado, Victorio M; Toural, Cristina; Martín, Daniel; Gomez-Lucia, Esperanza
2007-02-01
Laboratory diagnosis of feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) usually involves both viruses, as the clinical signs are similar and coinfection may occur. Serological methods may not represent an accurate diagnosis: maternal antibodies or cross-reactions may give false positive results to FIV, and false negative results may occur in latent FeLV status, or in certain FIV infection stages. A nested polymerase chain reaction (PCR) technique was designed to detect FeLV, FIV and feline endogenous retrovirus simultaneously. The detection of endogenous sequences was considered indicative of successful DNA extraction. The technique was used to diagnose FIV and FeLV in the blood cells of 179 cats. The kappa value with the serological data was 0.69 for FeLV and 0.87 for FIV. The joint detection of FeLV and FIV by this novel nested PCR is sensitive, specific, fast and convenient, and its applicability for clinical diagnosis is promising, as the direct evidence of the presence of the virus is more realistic than the indirect data provided by the serological detection.
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Video redaction: a survey and comparison of enabling technologies
NASA Astrophysics Data System (ADS)
Sah, Shagan; Shringi, Ameya; Ptucha, Raymond; Burry, Aaron; Loce, Robert
2017-09-01
With the prevalence of video recordings from smart phones, dash cams, body cams, and conventional surveillance cameras, privacy protection has become a major concern, especially in light of legislation such as the Freedom of Information Act. Video redaction is used to obfuscate sensitive and personally identifiable information. Today's typical workflow involves simple detection, tracking, and manual intervention. Automated methods rely on accurate detection mechanisms being paired with robust tracking methods across the video sequence to ensure the redaction of all sensitive information while minimizing spurious obfuscations. Recent studies have explored the use of convolution neural networks and recurrent neural networks for object detection and tracking. The present paper reviews the redaction problem and compares a few state-of-the-art detection, tracking, and obfuscation methods as they relate to redaction. The comparison introduces an evaluation metric that is specific to video redaction performance. The metric can be evaluated in a manner that allows balancing the penalty for false negatives and false positives according to the needs of particular application, thereby assisting in the selection of component methods and their associated hyperparameters such that the redacted video has fewer frames that require manual review.
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Mačkić-Đurović, Mirela; Projić, Petar; Ibrulj, Slavka; Cakar, Jasmina; Marjanović, Damir
2014-05-01
The goal of this study was to examine the effectiveness of 6 STR markers application (D21S1435, D21S11, D21S1270, D21S1411, D21S226 and IFNAR) in molecular genetic diagnostics of Down syndrome (DS) and to compare it with cytogenetic method. Testing was performed on 73 children, with the previously cytogenetically confirmed Down syndrome. DNA isolated from the buccal swab was used. Previously mentioned loci located on chromosome 21 were simultaneously amplified using quantitative fluorescence PCR (QF PCR). Using this method, 60 previously cytogenetically diagnosed DS with standard type of trisomy 21 were confirmed. Furthermore, six of eight children with mosaic type of DS were detected. Two false negative results for mosaic type of DS were obtained. Finally, five children with the translocation type of Down syndrome were also confirmed with this molecular test. In conclusion, molecular genetic analysis of STR loci is fast, cheap and simple method that could be used in detection of DS. Regarding possible false results detected for certain number of mosaic types, cytogenetic analysis should be used as a confirmatory test.
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Gitman, Melissa R; Ferguson, David; Landry, Marie L
2013-11-01
The Simplexa HSV 1 & 2 direct PCR assay was compared with conventional cell culture, cytospin-enhanced direct fluorescent antibody (DFA), and a laboratory-developed real-time TaqMan PCR (LDT HSV PCR) using extracted nucleic acid for the detection of herpes simplex virus (HSV) in dermal, genital, mouth, ocular, and other swab samples. One hundred seventy-one swabs were tested prospectively, and 58 were positive for HSV (34 HSV-1 and 24 HSV-2). Cytospin-DFA detected 50 (86.2%), conventional cell culture 51 (87.9%), Simplexa direct 55 (94.8%), and LDT HSV PCR 57 (98.3%) of 58 true positives. Simplexa direct detected more positives than DFA and culture, but the differences were not significant (P = 0.0736 and P = 0.3711, respectively, by the McNemar test). Samples that were positive by all methods (n = 48) were strong positives (LDT cycle threshold [CT] value, 14.4 to 26.1). One strongly positive sample was falsely negative by LDT HSV PCR due to a failure of TaqMan probe binding. Three samples falsely negative by Simplexa direct had high CT values by LDT HSV PCR (LDT CT, 35.8 to 38.2). Omission of the DNA extraction step by Simplexa direct led to a drop in sensitivity compared to the sensitivity of LDT HSV PCR using extracted samples (94.8% versus 98.3%, respectively), but the difference was not significant (P = 0.6171). Simplexa HSV 1 & 2 direct PCR was the most expensive but required the least training of the assays used, had the lowest hands-on time and fastest assay time (75 min, versus 3 h by LDT HSV PCR), and provided the HSV type.
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Gitman, Melissa R.; Ferguson, David
2013-01-01
The Simplexa HSV 1 & 2 direct PCR assay was compared with conventional cell culture, cytospin-enhanced direct fluorescent antibody (DFA), and a laboratory-developed real-time TaqMan PCR (LDT HSV PCR) using extracted nucleic acid for the detection of herpes simplex virus (HSV) in dermal, genital, mouth, ocular, and other swab samples. One hundred seventy-one swabs were tested prospectively, and 58 were positive for HSV (34 HSV-1 and 24 HSV-2). Cytospin-DFA detected 50 (86.2%), conventional cell culture 51 (87.9%), Simplexa direct 55 (94.8%), and LDT HSV PCR 57 (98.3%) of 58 true positives. Simplexa direct detected more positives than DFA and culture, but the differences were not significant (P = 0.0736 and P = 0.3711, respectively, by the McNemar test). Samples that were positive by all methods (n = 48) were strong positives (LDT cycle threshold [CT] value, 14.4 to 26.1). One strongly positive sample was falsely negative by LDT HSV PCR due to a failure of TaqMan probe binding. Three samples falsely negative by Simplexa direct had high CT values by LDT HSV PCR (LDT CT, 35.8 to 38.2). Omission of the DNA extraction step by Simplexa direct led to a drop in sensitivity compared to the sensitivity of LDT HSV PCR using extracted samples (94.8% versus 98.3%, respectively), but the difference was not significant (P = 0.6171). Simplexa HSV 1 & 2 direct PCR was the most expensive but required the least training of the assays used, had the lowest hands-on time and fastest assay time (75 min, versus 3 h by LDT HSV PCR), and provided the HSV type. PMID:24006008
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NASA Astrophysics Data System (ADS)
Pötzi, W.; Veronig, A. M.; Temmer, M.
2018-06-01
In the framework of the Space Situational Awareness program of the European Space Agency (ESA/SSA), an automatic flare detection system was developed at Kanzelhöhe Observatory (KSO). The system has been in operation since mid-2013. The event detection algorithm was upgraded in September 2017. All data back to 2014 was reprocessed using the new algorithm. In order to evaluate both algorithms, we apply verification measures that are commonly used for forecast validation. In order to overcome the problem of rare events, which biases the verification measures, we introduce a new event-based method. We divide the timeline of the Hα observations into positive events (flaring period) and negative events (quiet period), independent of the length of each event. In total, 329 positive and negative events were detected between 2014 and 2016. The hit rate for the new algorithm reached 96% (just five events were missed) and a false-alarm ratio of 17%. This is a significant improvement of the algorithm, as the original system had a hit rate of 85% and a false-alarm ratio of 33%. The true skill score and the Heidke skill score both reach values of 0.8 for the new algorithm; originally, they were at 0.5. The mean flare positions are accurate within {±} 1 heliographic degree for both algorithms, and the peak times improve from a mean difference of 1.7± 2.9 minutes to 1.3± 2.3 minutes. The flare start times that had been systematically late by about 3 minutes as determined by the original algorithm, now match the visual inspection within -0.47± 4.10 minutes.
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Kapan, Murat; Onder, Akin; Girgin, Sadullah; Ulger, Burak Veli; Firat, Ugur; Uslukaya, Omer; Oguz, Abdullah
2015-02-01
The aim of this study was to analyze the presence of malignancy in patients with Hashimoto's thyroiditis and to investigate the reliability of preoperative fine-needle aspiration biopsy (FNAB). The retrospective study included 44 patients who were operated on for nodular goiter between December 2010 and October 2011. The patients underwent thyroidectomy following a cytologic analysis plus FNAB. Hashimoto's thyroiditis was confirmed on histopathology in all patients. FNAB results were defined as benign in 14 (31.8%), suspicion for malignancy in 17 (38.6%), malignant in 9 (20.5%), and inadequate in 4 (9.1%). Following the thyroidectomy, presence of papillary thyroid carcinoma and follicular variant of papillary thyroid carcinoma were detected in 10 patients (22.7%) and 1 (2.3%) patient, respectively. The FNAB results were interpreted in terms of malignancy, which revealed the sensitivity as 80%; specificity, 40%; false positives, 69.2%; false negatives, 14.3%; positive predictive value, 31.8%; negative predictive value, 85.7%; and diagnostic accuracy, 50%. The coexistence of Hashimoto's thyroiditis with papillary thyroid carcinoma is quite common. The FNAB results for such cases are hard to evaluate, and they are likely to increase the number of false positives.
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van der Wilden, Gwendolyn M; Van der Wilden, Gwen; Albers, Christoph E; Albers, Christof; Haefeli, Pascal C; Haefeli, Peter; Zimmermann, Heinz; Zimmerman, Heinz; Exadaktylos, Aristomenis; Exadaktylos, Aris; Levy, Phillip; Birkhan, Oscar; Birkham, Oscar; Michaildou, Maria; Michailidou, Maria; Sideris, Antonios; Velmahos, George C; Velmahos, George; Alam, Hasan B; Alam, Hasan; King, David R; King, David; Fagenholz, Peter J; Fagenholz, Peter; Yeh, D Dante; Yeh, Dante; de Moya, Marc A
2012-12-01
Pneumothoraces (PTXs) are a common entity in thoracic trauma. Micropower impulse radar (MIR) has been able to detect PTXs in surgical patients. However, this technology has not been tested previously on trauma patients. The purpose of this study was to determine the sensitivity and specificity of MIR to detect clinically significant PTXs. We hypothesized that MIR technology can effectively screen trauma patients for clinically significant PTXs. This was a prospective observational study in Level I trauma centers in Boston, Massachusetts, and Bern, Switzerland. All trauma patients undergoing a chest computed tomographic (CT) scan were eligible for the study. Consent was obtained, and readings were performed within 30 minutes before or after the CT scan. The patients had eight lung fields tested (four on each side). The qualitative and quantitative MIR results were blinded and stored on the device. We then compared the results of the MIR to the CT scan and the need for chest tube drainage. We defined PTXs as clinically significant if they required a chest tube. Seventy-five patients were enrolled, with a mean age of 46 ± 16 years. Eighty-four percent were male. The screening test took approximately 1 minute. All but two patients had blunt chest trauma. Six true-positives, 6 false-positives, 63 true-negatives, and 0 false-negatives resulted in an overall sensitivity of 100%. MIR is an easy to use handheld technology that effectively screened patients for clinically significant PTXs, with a sensitivity and negative predictive value of 100%. MIR may be used for rapid, repeatable, and ongoing surveillance of trauma patients. Diagnostic study, level III.
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A Decision Theoretic Approach to Evaluate Radiation Detection Algorithms
DOE Office of Scientific and Technical Information (OSTI.GOV)
Nobles, Mallory A.; Sego, Landon H.; Cooley, Scott K.
2013-07-01
There are a variety of sensor systems deployed at U.S. border crossings and ports of entry that scan for illicit nuclear material. In this work, we develop a framework for comparing the performance of detection algorithms that interpret the output of these scans and determine when secondary screening is needed. We optimize each algorithm to minimize its risk, or expected loss. We measure an algorithm’s risk by considering its performance over a sample, the probability distribution of threat sources, and the consequence of detection errors. While it is common to optimize algorithms by fixing one error rate and minimizing another,more » our framework allows one to simultaneously consider multiple types of detection errors. Our framework is flexible and easily adapted to many different assumptions regarding the probability of a vehicle containing illicit material, and the relative consequences of a false positive and false negative errors. Our methods can therefore inform decision makers of the algorithm family and parameter values which best reduce the threat from illicit nuclear material, given their understanding of the environment at any point in time. To illustrate the applicability of our methods, in this paper, we compare the risk from two families of detection algorithms and discuss the policy implications of our results.« less
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Zhang, Yang; Chen, Fuming; Xue, Huijun; Li, Zhao; An, Qiang; Wang, Jianqi; Zhang, Yang
2016-01-01
Ultra-wideband (UWB) radar has been widely used for detecting human physiological signals (respiration, movement, etc.) in the fields of rescue, security, and medicine owing to its high penetrability and range resolution. In these applications, especially in rescue after disaster (earthquake, collapse, mine accident, etc.), the presence, number, and location of the trapped victims to be detected and rescued are the key issues of concern. Ample research has been done on the first issue, whereas the identification and localization of multi-targets remains a challenge. False positive and negative identification results are two common problems associated with the detection of multiple stationary human targets. This is mainly because the energy of the signal reflected from the target close to the receiving antenna is considerably stronger than those of the targets at further range, often leading to missing or false recognition if the identification method is based on the energy of the respiratory signal. Therefore, a novel method based on cross-correlation is proposed in this paper that is based on the relativity and periodicity of the signals, rather than on the energy. The validity of this method is confirmed through experiments using different scenarios; the results indicate a discernible improvement in the detection precision and identification of the multiple stationary targets. PMID:27801795
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Zhang, Yang; Chen, Fuming; Xue, Huijun; Li, Zhao; An, Qiang; Wang, Jianqi; Zhang, Yang
2016-10-27
Ultra-wideband (UWB) radar has been widely used for detecting human physiological signals (respiration, movement, etc.) in the fields of rescue, security, and medicine owing to its high penetrability and range resolution. In these applications, especially in rescue after disaster (earthquake, collapse, mine accident, etc.), the presence, number, and location of the trapped victims to be detected and rescued are the key issues of concern. Ample research has been done on the first issue, whereas the identification and localization of multi-targets remains a challenge. False positive and negative identification results are two common problems associated with the detection of multiple stationary human targets. This is mainly because the energy of the signal reflected from the target close to the receiving antenna is considerably stronger than those of the targets at further range, often leading to missing or false recognition if the identification method is based on the energy of the respiratory signal. Therefore, a novel method based on cross-correlation is proposed in this paper that is based on the relativity and periodicity of the signals, rather than on the energy. The validity of this method is confirmed through experiments using different scenarios; the results indicate a discernible improvement in the detection precision and identification of the multiple stationary targets.
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Somily, Ali M; Barry, Mazin A; Habib, Hanan A; Alotaibi, Fawzia E; Al-Zamil, Fahad A; Khan, Mohammed A; Sarwar, Mohammed S; Bakhash, Nawab D; Alrabiaah, Abdulkarim A; Shakoor, Zahid A; Senok, Abiola C
2016-12-01
To assess the performance of Xpert MTB/RIF, an automated molecular test for Mycobacterium tuberculosis (MTB) and resistance to rifampin (RIF), against smear microscopy and culture method for diagnosis of MTB infection. Methods: This is a retrospective analysis of 103 respiratory and 137 non-respiratory patient specimens suspected of tuberculosis at King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia performed between April 2014 and March 2015. Each sample underwent smear microscopy, mycobacterial culture, and GeneXpert MTB/RIF test. Results: Fifteen out of 103 respiratory samples were smear and culture positive, whereas 9 out of 137 non-respiratory samples were smear positive. Out of 9 smear positive specimens, 8 were also culture positive. All 15 culture positive respiratory samples were detected by Xpert MTB/RIF (sensitivity and positive predictive value [PPV]=100%). Similarly, all 8 culture positive non-respiratory specimens were identified by Xpert MTB/RIF (sensitivity 100%; PPV 88.8%). The Xpert MTB/RIF detected only one false positive result in 88 smear negative respiratory specimens (specificity 98.9%; negative predictive value [NPV]= 100%). All 125 smear negative non-respiratory specimens tested negative by culture and Xpert MTB/RIF (sensitivity, specificity, PPV, NPV= 100%). Conclusion: The performance of Xpert MTB/RIF was comparable to the gold standard culture method for identification of MTB in both respiratory and non-respiratory clinical specimens.
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Somily, Ali M.; Barry, Mazin A.; Habib, Hanan A.; Alotaibi, Fawzia E.; Al-Zamil, Fahad A.; Khan, Mohammed A.; Sarwar, Mohammed S.; Bakhash, Nawab D.; Alrabiaah, Abdulkarim A.; Shakoor, Zahid A.; Senok, Abiola C.
2016-01-01
Objectives To assess the performance of Xpert MTB/RIF, an automated molecular test for Mycobacterium tuberculosis (MTB) and resistance to rifampin (RIF), against smear microscopy and culture method for diagnosis of MTB infection. Methods This is a retrospective analysis of 103 respiratory and 137 non-respiratory patient specimens suspected of tuberculosis at King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia performed between April 2014 and March 2015. Each sample underwent smear microscopy, mycobacterial culture, and GeneXpert MTB/RIF test. Results Fifteen out of 103 respiratory samples were smear and culture positive, whereas 9 out of 137 non-respiratory samples were smear positive. Out of 9 smear positive specimens, 8 were also culture positive. All 15 culture positive respiratory samples were detected by Xpert MTB/RIF (sensitivity and positive predictive value [PPV]=100%). Similarly, all 8 culture positive non-respiratory specimens were identified by Xpert MTB/RIF (sensitivity 100%; PPV 88.8%). The Xpert MTB/RIF detected only one false positive result in 88 smear negative respiratory specimens (specificity 98.9%; negative predictive value [NPV]= 100%). All 125 smear negative non-respiratory specimens tested negative by culture and Xpert MTB/RIF (sensitivity, specificity, PPV, NPV= 100%). Conclusion The performance of Xpert MTB/RIF was comparable to the gold standard culture method for identification of MTB in both respiratory and non-respiratory clinical specimens. PMID:27874159
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Schröder, Jan; Hsu, Arthur; Boyle, Samantha E.; Macintyre, Geoff; Cmero, Marek; Tothill, Richard W.; Johnstone, Ricky W.; Shackleton, Mark; Papenfuss, Anthony T.
2014-01-01
Motivation: Methods for detecting somatic genome rearrangements in tumours using next-generation sequencing are vital in cancer genomics. Available algorithms use one or more sources of evidence, such as read depth, paired-end reads or split reads to predict structural variants. However, the problem remains challenging due to the significant computational burden and high false-positive or false-negative rates. Results: In this article, we present Socrates (SOft Clip re-alignment To idEntify Structural variants), a highly efficient and effective method for detecting genomic rearrangements in tumours that uses only split-read data. Socrates has single-nucleotide resolution, identifies micro-homologies and untemplated sequence at break points, has high sensitivity and high specificity and takes advantage of parallelism for efficient use of resources. We demonstrate using simulated and real data that Socrates performs well compared with a number of existing structural variant detection tools. Availability and implementation: Socrates is released as open source and available from http://bioinf.wehi.edu.au/socrates. Contact: papenfuss@wehi.edu.au Supplementary information: Supplementary data are available at Bioinformatics online. PMID:24389656
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Shimelis, Techalew; Tadesse, Endale
2015-01-01
Objective To determine the diagnostic performance of the SD BIOLINE HIV/syphilis Duo rapid test. Design A hospital-based cross-sectional study. Setting This evaluation was conducted at one of the largest hospitals in southern Ethiopia. Participants Serum samples obtained from clients attending the antiretroviral therapy and voluntary counselling and testing centres were used. Sera were originally collected for the purpose of investigating syphilis epidemiology. The performance of the test to detect HIV was evaluated using 400 sera (200 HIV positives and 200 HIV negatives). Also, its performance to detect syphilis was evaluated using 85 syphilis positive and 100 syphilis negative serum samples. Individuals <15 years of age or syphilis treated or those with ≤50 cells/µL CD4 cell count were originally excluded. Outcome measures HIV screening was carried out according to the national rapid diagnostic testing (RDT) algorithm: Shenghai Kehua Bioengineering (KHB) test kit as a screening test, followed by the HIV1/2 STAT-PAK assay if positive. Where the result of the STAT-PAK is discordant with KHB, Unigold HIV is used as a tiebreaker to determine the result. We also used ELISA to resolve discordant HIV results. Syphilis serostatus was determined using the Treponema pallidum haemagglutination assay (TPHA). Results The respective sensitivity, specificity, positive predictive value and negative predictive value of the SD BIOLINE HIV/syphilis Duo test were 100, 99.5, 99.5 and 100% for HIV and 97.6, 96, 95.4 and 98% for syphilis testing, respectively. In reference to TPHA, the test kit reported 4 false positives and 2 false negative results for syphilis. The κ values were 0.99 for HIV testing and 0.94 for syphilis testing. Conclusions The excellent performance of the SD BIOLINE HIV/syphilis Duo test to detect HIV as well as syphilis facilitates the integration of syphilis testing and treatment to the already established HIV prevention programme, ultimately contributing to the dual HIV and syphilis elimination goal. PMID:25908677
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Shimelis, Techalew; Tadesse, Endale
2015-04-23
To determine the diagnostic performance of the SD BIOLINE HIV/syphilis Duo rapid test. A hospital-based cross-sectional study. This evaluation was conducted at one of the largest hospitals in southern Ethiopia. Serum samples obtained from clients attending the antiretroviral therapy and voluntary counselling and testing centres were used. Sera were originally collected for the purpose of investigating syphilis epidemiology. The performance of the test to detect HIV was evaluated using 400 sera (200 HIV positives and 200 HIV negatives). Also, its performance to detect syphilis was evaluated using 85 syphilis positive and 100 syphilis negative serum samples. Individuals <15 years of age or syphilis treated or those with ≤50 cells/µL CD4 cell count were originally excluded. HIV screening was carried out according to the national rapid diagnostic testing (RDT) algorithm: Shenghai Kehua Bioengineering (KHB) test kit as a screening test, followed by the HIV1/2 STAT-PAK assay if positive. Where the result of the STAT-PAK is discordant with KHB, Unigold HIV is used as a tiebreaker to determine the result. We also used ELISA to resolve discordant HIV results. Syphilis serostatus was determined using the Treponema pallidum haemagglutination assay (TPHA). The respective sensitivity, specificity, positive predictive value and negative predictive value of the SD BIOLINE HIV/syphilis Duo test were 100, 99.5, 99.5 and 100% for HIV and 97.6, 96, 95.4 and 98% for syphilis testing, respectively. In reference to TPHA, the test kit reported 4 false positives and 2 false negative results for syphilis. The κ values were 0.99 for HIV testing and 0.94 for syphilis testing. The excellent performance of the SD BIOLINE HIV/syphilis Duo test to detect HIV as well as syphilis facilitates the integration of syphilis testing and treatment to the already established HIV prevention programme, ultimately contributing to the dual HIV and syphilis elimination goal. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
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Observer training for computer-aided detection of pulmonary nodules in chest radiography.
De Boo, Diederick W; van Hoorn, François; van Schuppen, Joost; Schijf, Laura; Scheerder, Maeke J; Freling, Nicole J; Mets, Onno; Weber, Michael; Schaefer-Prokop, Cornelia M
2012-08-01
To assess whether short-term feedback helps readers to increase their performance using computer-aided detection (CAD) for nodule detection in chest radiography. The 140 CXRs (56 with a solitary CT-proven nodules and 84 negative controls) were divided into four subsets of 35; each were read in a different order by six readers. Lesion presence, location and diagnostic confidence were scored without and with CAD (IQQA-Chest, EDDA Technology) as second reader. Readers received individual feedback after each subset. Sensitivity, specificity and area under the receiver-operating characteristics curve (AUC) were calculated for readings with and without CAD with respect to change over time and impact of CAD. CAD stand-alone sensitivity was 59 % with 1.9 false-positives per image. Mean AUC slightly increased over time with and without CAD (0.78 vs. 0.84 with and 0.76 vs. 0.82 without CAD) but differences did not reach significance. The sensitivity increased (65 % vs. 70 % and 66 % vs. 70 %) and specificity decreased over time (79 % vs. 74 % and 80 % vs. 77 %) but no significant impact of CAD was found. Short-term feedback does not increase the ability of readers to differentiate true- from false-positive candidate lesions and to use CAD more effectively. • Computer-aided detection (CAD) is increasingly used as an adjunct for many radiological techniques. • Short-term feedback does not improve reader performance with CAD in chest radiography. • Differentiation between true- and false-positive CAD for low conspicious possible lesions proves difficult. • CAD can potentially increase reader performance for nodule detection in chest radiography.
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Valence and the development of immediate and long-term false memory illusions.
Howe, Mark L; Candel, Ingrid; Otgaar, Henry; Malone, Catherine; Wimmer, Marina C
2010-01-01
Across five experiments we examined the role of valence in children's and adults' true and false memories. Using the Deese/Roediger-McDermott paradigm and either neutral or negative-emotional lists, both adults' (Experiment 1) and children's (Experiment 2) true recall and recognition was better for neutral than negative items, and although false recall was also higher for neutral items, false recognition was higher for negative items. The last three experiments examined adults' (Experiment 3) and children's (Experiments 4 and 5) 1-week long-term recognition of neutral and negative-emotional information. The results replicated the immediate recall and recognition findings from the first two experiments. More important, these experiments showed that although true recognition decreased over the 1-week interval, false recognition of neutral items remained unchanged whereas false recognition of negative-emotional items increased. These findings are discussed in terms of theories of emotion and memory as well as their forensic implications.
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Monier, I; Blondel, B; Ego, A; Kaminiski, M; Goffinet, F; Zeitlin, J
2015-03-01
To assess the proportion of small for gestational age (SGA) and normal birthweight infants suspected of fetal growth restriction (FGR) during pregnancy, and to investigate obstetric and neonatal outcomes by suspicion of FGR and SGA status at birth. Population-based study. All French maternity units in 2010. Representative sample of singleton births (n = 14,100). We compared SGA infants with a birthweight of less than the 10th percentile suspected of FGR, defined as mention of FGR in medical charts (true positives), non-SGA infants suspected of FGR (false positives), SGA infants without suspicion of FGR (false negatives) and non-SGA infants without suspicion of FGR (true negatives). Multivariable analyses were adjusted for maternal and neonatal characteristics hypothesised to affect closer surveillance for FGR and our outcomes. Obstetric management (caesarean, provider-initiated preterm and early term delivery) and neonatal outcomes (late fetal death, preterm birth, Apgar score, resuscitation at birth). 21.7% of SGA infants (n = 265) and 2.1% of non-SGA infants (n = 271) were suspected of FGR during pregnancy. Compared with true negatives, provider-initiated preterm deliveries were higher for true and false positives (adjusted risk ratio [aRR], 6.1 [95% CI, 3.8-9.8] and 4.6 [95% CI, 3.2-6.7]), but not for false negatives (aRR, 1.1 [95% CI, 0.6-1.9]). Neonatal outcomes were not better for SGA infants if FGR was suspected. Antenatal suspicion of FGR among SGA infants was low and one-half of infants suspected of FGR were not SGA. The increased risk of provider-initiated delivery observed in non-SGA infants suspected of FGR raises concerns about the iatrogenic consequences of screening. © 2014 The Authors BJOG An International Journal of Obstetrics and Gynaecology published by John Wiley & Sons Ltd on behalf of Royal College of Obstetricians and Gynaecologists.
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Wang, Yuexia; Yang, Ming; Liu, Shuchun; Chen, Wanyi; Suo, Biao
2015-09-01
Real-time polymerase chain reaction (PCR) allows rapid detection of Salmonella in frozen dairy products, but it might cause a false positive detection result because it might amplify DNA from dead target cells as well. In this study, Salmonella-free frozen ice cream was initially inoculated with heat-killed Salmonella Typhimurium cells and stored at -18°C. Bacterial DNA extracted from the sample was amplified using TaqMan probe-based real-time PCR targeting the invA gene. Our results indicated that DNA from the dead cells remained stable in frozen ice cream for at least 20 days, and could produce fluorescence signal for real-time PCR as well. To overcome this limitation, propidium monoazide (PMA) was combined with real-time PCR. PMA treatment can effectively prevent PCR amplification from heat-killed Salmonella cells in frozen ice cream. The PMA real-time PCR assay can selectively detect viable Salmonella at as low as 10 3 CFU/mL. Combining 18 hours of pre-enrichment with the assay allows for the detection of viable Salmonella at 10 0 CFU/mL and avoiding the false-positive result of dead cells. The PMA real-time PCR assay provides an alternative specifically for detection of viable Salmonella in ice cream. However, when the PMA real-time PCR assay was evaluated in ice cream subjected to frozen storage, it obviously underestimated the contamination situation of viable Salmonella, which might lead to a false negative result. According to this result, the use of enrichment prior to PMA real-time PCR analysis remains as the more appropriate approach. Copyright © 2015. Published by Elsevier B.V.
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Pulse Oximetry and Auscultation for Congenital Heart Disease Detection.
Hu, Xiao-Jing; Ma, Xiao-Jing; Zhao, Qu-Ming; Yan, Wei-Li; Ge, Xiao-Ling; Jia, Bing; Liu, Fang; Wu, Lin; Ye, Ming; Liang, Xue-Cun; Zhang, Jing; Gao, Yan; Zhai, Xiao-Wen; Huang, Guo-Ying
2017-10-01
Pulse oximetry (POX) has been confirmed as a specific screening modality for critical congenital heart disease (CCHD), with moderate sensitivity. However, POX is not able to detect most serious and critical cardiac lesions (major congenital heart disease [CHD]) without hypoxemia. In this study, we investigated the accuracy and feasibility of the addition of cardiac auscultation to POX as a screening method for asymptomatic major CHD. A multicenter prospective observational screening study was conducted at 15 hospitals in Shanghai between July 1, 2012, and December 31, 2014. Newborns with either an abnormal POX or cardiac auscultation were defined as screen positive. All screen-positive newborns underwent further echocardiography. False-negative results were identified by clinical follow-up, parents' feedback, and telephone review. We assessed the accuracy of POX plus cardiac auscultation for the detection of major CHD. CHD screening was completed in all 15 hospitals, with a screening rate of 94.0% to 99.8%. In total, 167 190 consecutive asymptomatic newborn infants were screened, of which 203 had major CHD (44 critical and 159 serious). The sensitivity of POX plus cardiac auscultation was 95.5% (95% confidence interval 84.9%-98.7%) for CCHD and 92.1% (95% confidence interval 87.7%-95.1%) for major CHD. The false-positive rate was 1.2% for detecting CCHD and 1.1% for detecting major CHD. In our current study, we show that using POX plus cardiac auscultation significantly improved the detection rate of major CHD in the early neonatal stage, with high sensitivity and a reasonable false-positive rate. It provides strong evidence and a reliable method for neonatal CHD screening. Copyright © 2017 by the American Academy of Pediatrics.
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Obscenity detection using haar-like features and Gentle Adaboost classifier.
Mustafa, Rashed; Min, Yang; Zhu, Dingju
2014-01-01
Large exposure of skin area of an image is considered obscene. This only fact may lead to many false images having skin-like objects and may not detect those images which have partially exposed skin area but have exposed erotogenic human body parts. This paper presents a novel method for detecting nipples from pornographic image contents. Nipple is considered as an erotogenic organ to identify pornographic contents from images. In this research Gentle Adaboost (GAB) haar-cascade classifier and haar-like features used for ensuring detection accuracy. Skin filter prior to detection made the system more robust. The experiment showed that, considering accuracy, haar-cascade classifier performs well, but in order to satisfy detection time, train-cascade classifier is suitable. To validate the results, we used 1198 positive samples containing nipple objects and 1995 negative images. The detection rates for haar-cascade and train-cascade classifiers are 0.9875 and 0.8429, respectively. The detection time for haar-cascade is 0.162 seconds and is 0.127 seconds for train-cascade classifier.
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Xu, Benjin; Liu, Ling; Liu, Li; Li, Xinping; Li, Xiaofang; Wang, Xin
2012-11-01
Methicillin-resistant Staphylococcus aureus (MRSA) is a global health concern, which had been detected in food and food production animals. Conventional testing for detection of MRSA takes 3 to 5 d to yield complete information of the organism and its antibiotic sensitivity pattern. So, a rapid method is needed to diagnose and treat the MRSA infections. The present study focused on the development of a multiplex PCR assay for the rapid and sensitive detection of MRSA. The assay simultaneously detected 4 genes, namely, 16S rRNA of the Staphylococcus genus, femA of S. aureus, mecA that encodes methicillin resistance, and one internal control. It was rapid and yielded results within 4 h. The analytical sensitivity and specificity of the multiplex PCR assay was evaluated by comparing it with the conventional method. The analytical sensitivity of the multiplex PCR assay at the DNA level was 10 ng DNA. The analytical specificity was evaluated with 10 reference staphylococci strains and was 100%. The diagnostic evaluation of MRSA was carried out using 360 foodborne staphylococci isolates, and showed 99.1% of specificity, 96.4% of sensitivity, 97.5% of positive predictive value, and 97.3% of negative predictive value compared to the conventional method. The inclusion of an internal control in the multiplex PCR assay is important to exclude false-negative cases. This test can be used as an effective diagnostic and surveillance tool to investigate the spread and emergence of MRSA. © 2012 Institute of Food Technologists®
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Stewart, Grant D; Van Neste, Leander; Delvenne, Philippe; Delrée, Paul; Delga, Agnès; McNeill, S Alan; O'Donnell, Marie; Clark, James; Van Criekinge, Wim; Bigley, Joseph; Harrison, David J
2013-03-01
Concern about possible false-negative prostate biopsy histopathology findings often leads to rebiopsy. A quantitative methylation specific polymerase chain reaction assay panel, including GSTP1, APC and RASSF1, could increase the sensitivity of detecting cancer over that of pathological review alone, leading to a high negative predictive value and a decrease in unnecessary repeat biopsies. The MATLOC study blindly tested archived prostate biopsy needle core tissue samples of 498 subjects from the United Kingdom and Belgium with histopathologically negative prostate biopsies, followed by positive (cases) or negative (controls) repeat biopsy within 30 months. Clinical performance of the epigenetic marker panel, emphasizing negative predictive value, was assessed and cross-validated. Multivariate logistic regression was used to evaluate all risk factors. The epigenetic assay performed on the first negative biopsies of this retrospective review cohort resulted in a negative predictive value of 90% (95% CI 87-93). In a multivariate model correcting for patient age, prostate specific antigen, digital rectal examination and first biopsy histopathological characteristics the epigenetic assay was a significant independent predictor of patient outcome (OR 3.17, 95% CI 1.81-5.53). A multiplex quantitative methylation specific polymerase chain reaction assay determining the methylation status of GSTP1, APC and RASSF1 was strongly associated with repeat biopsy outcome up to 30 months after initial negative biopsy in men with suspicion of prostate cancer. Adding this epigenetic assay could improve the prostate cancer diagnostic process and decrease unnecessary repeat biopsies. Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.
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Automatic Fall Detection System Based on the Combined Use of a Smartphone and a Smartwatch.
Casilari, Eduardo; Oviedo-Jiménez, Miguel A
2015-01-01
Due to their widespread popularity, decreasing costs, built-in sensors, computing power and communication capabilities, Android-based personal devices are being seen as an appealing technology for the deployment of wearable fall detection systems. In contrast with previous solutions in the existing literature, which are based on the performance of a single element (a smartphone), this paper proposes and evaluates a fall detection system that benefits from the detection performed by two popular personal devices: a smartphone and a smartwatch (both provided with an embedded accelerometer and a gyroscope). In the proposed architecture, a specific application in each component permanently tracks and analyses the patient's movements. Diverse fall detection algorithms (commonly employed in the literature) were implemented in the developed Android apps to discriminate falls from the conventional activities of daily living of the patient. As a novelty, a fall is only assumed to have occurred if it is simultaneously and independently detected by the two Android devices (which can interact via Bluetooth communication). The system was systematically evaluated in an experimental testbed with actual test subjects simulating a set of falls and conventional movements associated with activities of daily living. The tests were repeated by varying the detection algorithm as well as the pre-defined mobility patterns executed by the subjects (i.e., the typology of the falls and non-fall movements). The proposed system was compared with the cases where only one device (the smartphone or the smartwatch) is considered to recognize and discriminate the falls. The obtained results show that the joint use of the two detection devices clearly increases the system's capability to avoid false alarms or 'false positives' (those conventional movements misidentified as falls) while maintaining the effectiveness of the detection decisions (that is to say, without increasing the ratio of 'false negatives' or actual falls that remain undetected).
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Kodani, Maja; Mixson-Hayden, Tonya; Drobeniuc, Jan; Kamili, Saleem
2014-10-01
Five viruses have been etiologically associated with viral hepatitis. Nucleic acid testing (NAT) remains the gold standard for diagnosis of viremic stages of infection. NAT methodologies have been developed for all hepatitis viruses; however, a NAT-based assay that can simultaneously detect all five viruses is not available. We designed TaqMan card-based assays for detection of HAV RNA, HBV DNA, HCV RNA, HDV RNA and HEV RNA. The performances of individual assays were evaluated on TaqMan Array Cards (TAC) for detecting five viral genomes simultaneously. Sensitivity and specificity were determined by testing 329 NAT-tested clinical specimens. All NAT-positive samples for HCV (n = 32), HDV (n = 28) and HEV (n = 14) were also found positive in TAC (sensitivity, 100%). Forty-three of 46 HAV-NAT positive samples were also positive in TAC (sensitivity, 94%), while 36 of 39 HBV-NAT positive samples were positive (sensitivity, 92%). No false-positives were detected for HBV (n = 32), HCV (n = 36), HDV (n = 30), and HEV (n = 31) NAT-negative samples (specificity 100%), while 38 of 41 HAV-NAT negative samples were negative by TAC (specificity 93%). TAC assay was concordant with corresponding individual NATs for hepatitis A-E viral genomes and can be used for their detection simultaneously. The TAC assay has potential for use in hepatitis surveillance, for screening of donor specimens and in outbreak situations. Wider availability of TAC-ready assays may allow for customized assays, for improving acute jaundice surveillance and for other purposes for which there is need to identify multiple pathogens rapidly. Published by Elsevier B.V.
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Is the 15∆ Base in Prism Test Reliable for Detection of Amblyopia in Anisometropic Patients?
Burggraaf, F; Verkaik-Rijneveld, M C; Wubbels, R J; de Jongh, E
2017-09-01
The 15∆ base in prism test (15∆BIPT) introduced by Gobin is often used in The Netherlands to detect fixation preference, especially in young and preverbal children in whom a reliable measurement of the visual acuity (VA) is difficult. It is assumed that the fixation preference detected by the 15∆BIPT can be used to predict the presence of amblyopia. The aim of this retrospective case note review was to investigate the accuracy of the 15∆BIPT in detection of amblyopia in anisometropic patients. Four hundred and twelve files of anisometropic patients visiting the orthoptic department of The Rotterdam Eye Hospital were analyzed. Amblyopia was defined as an intraocular difference in VA of 2 or more Snellen lines. The sensitivity, specificity, and positive and negative predictive values of the 15∆BIPT were calculated and the receiver operating characteristic (ROC) curve was plotted. One hundred and fifty-two patients ranging from 3.3-13.1 years of age (median 5.4 years) met the inclusion criteria. One hundred and two patients were diagnosed with amblyopia. Best-corrected median VA of the best eye was 1.0 (range 0.5-1.2) and the worst eye 0.70 (range 0.05-1.2). Sensitivity of the 15∆BIPT (based on detecting amblyopia) was 34.3%. Specificity was 88.0%. The positive predictive value was 85.4% versus a negative predictive value of 39.6%. The area under the ROC curve (AUC) was 0.65 (95% CI 0.56-0.74). The low sensitivity, large number of false negatives and the AUC show that the 15∆BIPT can be considered a poor test for detecting amblyopia in anisometropic patients.
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Koolen, Bas B; Vrancken Peeters, Marie-Jeanne T F D; Aukema, Tjeerd S; Vogel, Wouter V; Oldenburg, Hester S A; van der Hage, Jos A; Hoefnagel, Cornelis A; Stokkel, Marcel P M; Loo, Claudette E; Rodenhuis, Sjoerd; Rutgers, Emiel J Th; Valdés Olmos, Renato A
2012-01-01
The aim of the present study was to investigate if 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) outperforms conventional imaging techniques for excluding distant metastases prior to neoadjuvant chemotherapy (NAC) treatment in patients with stage II and III breast cancer. Second, we assessed the clinical importance of false positive findings. One hundred and fifty four patients with stage II or III breast cancer, scheduled to receive NAC, underwent an 18F-FDG PET/CT scan and conventional imaging, consisting of bone scintigraphy, ultrasound of the liver, and chest radiography. Suspect additional lesions at staging examination were confirmed by biopsy and histopathology and/or additional imaging. Metastases that were detected within 6 months after the PET/CT scan were considered evidence of occult metastasis, missed by staging examination. Forty-two additional distant lesions were seen in 25 patients with PET/CT and could be confirmed in 20 (13%) of 154 patients. PET/CT was false positive for 8 additional lesions (19%) and misclassified the presence of metastatic disease in 5 (3%) of 154 patients. In 16 (80%) of 20 patients, additional lesions were exclusively seen with PET/CT, leading to a change in treatment in 13 (8%) of 154 patients. In 129 patients with a negative staging PET/CT, no metastases developed during the follow-up of 9.0 months. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of PET/CT in the detection of additional distant lesions in patients with stage II or III breast cancer are 100, 96, 80, 100, and 97%, respectively. FDG PET/CT is superior to conventional imaging techniques in the detection of distant metastases in patients with untreated stage II or III breast cancer and is associated with a low false positive rate. PET/CT may be of additional value in the staging of breast cancer prior to NAC.
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Minuzzi-Souza, Thaís Tâmara Castro; Nitz, Nadjar; Cuba, César Augusto Cuba; Hagström, Luciana; Hecht, Mariana Machado; Santana, Camila; Ribeiro, Marcelle; Vital, Tamires Emanuele; Santalucia, Marcelo; Knox, Monique; Obara, Marcos Takashi; Abad-Franch, Fernando; Gurgel-Gonçalves, Rodrigo
2018-01-09
Vector-borne pathogens threaten human health worldwide. Despite their critical role in disease prevention, routine surveillance systems often rely on low-complexity pathogen detection tests of uncertain accuracy. In Chagas disease surveillance, optical microscopy (OM) is routinely used for detecting Trypanosoma cruzi in its vectors. Here, we use replicate T. cruzi detection data and hierarchical site-occupancy models to assess the reliability of OM-based T. cruzi surveillance while explicitly accounting for false-negative and false-positive results. We investigated 841 triatomines with OM slides (1194 fresh, 1192 Giemsa-stained) plus conventional (cPCR, 841 assays) and quantitative PCR (qPCR, 1682 assays). Detections were considered unambiguous only when parasitologists unmistakably identified T. cruzi in Giemsa-stained slides. qPCR was >99% sensitive and specific, whereas cPCR was ~100% specific but only ~55% sensitive. In routine surveillance, examination of a single OM slide per vector missed ~50-75% of infections and wrongly scored as infected ~7% of the bugs. qPCR-based and model-based infection frequency estimates were nearly three times higher, on average, than OM-based indices. We conclude that the risk of vector-borne Chagas disease may be substantially higher than routine surveillance data suggest. The hierarchical modelling approach we illustrate can help enhance vector-borne disease surveillance systems when pathogen detection is imperfect.
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Comparison and characterization of Android-based fall detection systems.
Luque, Rafael; Casilari, Eduardo; Morón, María-José; Redondo, Gema
2014-10-08
Falls are a foremost source of injuries and hospitalization for seniors. The adoption of automatic fall detection mechanisms can noticeably reduce the response time of the medical staff or caregivers when a fall takes place. Smartphones are being increasingly proposed as wearable, cost-effective and not-intrusive systems for fall detection. The exploitation of smartphones' potential (and in particular, the Android Operating System) can benefit from the wide implantation, the growing computational capabilities and the diversity of communication interfaces and embedded sensors of these personal devices. After revising the state-of-the-art on this matter, this study develops an experimental testbed to assess the performance of different fall detection algorithms that ground their decisions on the analysis of the inertial data registered by the accelerometer of the smartphone. Results obtained in a real testbed with diverse individuals indicate that the accuracy of the accelerometry-based techniques to identify the falls depends strongly on the fall pattern. The performed tests also show the difficulty to set detection acceleration thresholds that allow achieving a good trade-off between false negatives (falls that remain unnoticed) and false positives (conventional movements that are erroneously classified as falls). In any case, the study of the evolution of the battery drain reveals that the extra power consumption introduced by the Android monitoring applications cannot be neglected when evaluating the autonomy and even the viability of fall detection systems.
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Liu, Jin-Ya; Chen, Li-Da; Cai, Hua-Song; Liang, Jin-Yu; Xu, Ming; Huang, Yang; Li, Wei; Feng, Shi-Ting; Xie, Xiao-Yan; Lu, Ming-De; Wang, Wei
2016-01-01
AIM: To present our initial experience regarding the feasibility of ultrasound virtual endoscopy (USVE) and its measurement reliability for polyp detection in an in vitro study using pig intestine specimens. METHODS: Six porcine intestine specimens containing 30 synthetic polyps underwent USVE, computed tomography colonography (CTC) and optical colonoscopy (OC) for polyp detection. The polyp measurement defined as the maximum polyp diameter on two-dimensional (2D) multiplanar reformatted (MPR) planes was obtained by USVE, and the absolute measurement error was analyzed using the direct measurement as the reference standard. RESULTS: USVE detected 29 (96.7%) of 30 polyps, remaining a 7-mm one missed. There was one false-positive finding. Twenty-six (89.7%) of 29 reconstructed images were clearly depicted, while 29 (96.7%) of 30 polyps were displayed on CTC with one false-negative finding. In OC, all the polyps were detected. The intraclass correlation coefficient was 0.876 (95%CI: 0.745-0.940) for measurements obtained with USVE. The pooled absolute measurement errors ± the standard deviations of the depicted polyps with actual sizes ≤ 5 mm, 6-9 mm, and ≥ 10 mm were 1.9 ± 0.8 mm, 0.9 ± 1.2 mm, and 1.0 ± 1.4 mm, respectively. CONCLUSION: USVE is reliable for polyp detection and measurement in in vitro study. PMID:27022217
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Comparison and Characterization of Android-Based Fall Detection Systems
Luque, Rafael; Casilari, Eduardo; Morón, María-José; Redondo, Gema
2014-01-01
Falls are a foremost source of injuries and hospitalization for seniors. The adoption of automatic fall detection mechanisms can noticeably reduce the response time of the medical staff or caregivers when a fall takes place. Smartphones are being increasingly proposed as wearable, cost-effective and not-intrusive systems for fall detection. The exploitation of smartphones' potential (and in particular, the Android Operating System) can benefit from the wide implantation, the growing computational capabilities and the diversity of communication interfaces and embedded sensors of these personal devices. After revising the state-of-the-art on this matter, this study develops an experimental testbed to assess the performance of different fall detection algorithms that ground their decisions on the analysis of the inertial data registered by the accelerometer of the smartphone. Results obtained in a real testbed with diverse individuals indicate that the accuracy of the accelerometry-based techniques to identify the falls depends strongly on the fall pattern. The performed tests also show the difficulty to set detection acceleration thresholds that allow achieving a good trade-off between false negatives (falls that remain unnoticed) and false positives (conventional movements that are erroneously classified as falls). In any case, the study of the evolution of the battery drain reveals that the extra power consumption introduced by the Android monitoring applications cannot be neglected when evaluating the autonomy and even the viability of fall detection systems. PMID:25299953
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Renal damage detected by DMSA, despite normal renal ultrasound, in children with febrile UTI.
Bush, N C; Keays, M; Adams, C; Mizener, K; Pritzker, K; Smith, W; Traylor, J; Villanueva, C; Snodgrass, W T
2015-06-01
2011 American Academy of Pediatrics guidelines recommended renal-bladder ultrasound (RBUS) as the only evaluation after febrile urinary tract infection (FUTI) in infants aged 2-24 months. We determined the sensitivity, specificity, and false negative rate of RBUS to identify DMSA-detected renal damage in this age group as well as in older children. Consecutive patients referred to pediatric urology with a history of FUTI underwent DMSA ≥ 3 months after FUTI. Abnormal RBUS was defined as: Society of Fetal Urology hydronephrosis grades I-IV; hydroureter ≥ 7 mm; renal scar defined as focal parenchymal thinning; and/or size discrepancy ≥ 1 cm between kidneys. Abnormal DMSA was presence of any focal uptake defects and/or split renal function < 44%. We calculated sensitivity, specificity, positive and negative predictive values, and false negative rates of RBUS compared to DMSA. 618 patients (79% female), median age 3.4 years, were referred for FUTIs. Of the 512 (83%) with normal RBUS, 99 (19%) had abnormal DMSA. Children with normal RBUS after their first FUTI had abnormal DMSA in 15/151 (10%) aged ≤ 24 months and 23/119 (19%) aged > 24 months. RBUS had poor sensitivity (34%) and low positive predictive value (47%) to identify patients with renal damage. 99/149 (66%) children with renal damage on DMSA had normal RBUS. After FUTI, 66% of children with reduced renal function and/or renal cortical defects found by DMSA scintigraphy had a normal RBUS. Since abnormal DMSA may correlate with increased risk for VUR, recurrent FUTI and renal damage, our data suggest RBUS alone will fail to detect a significant proportion of patients at risk. The data suggest that imaging after FUTI should include acute RBUS and delayed DMSA, reserving VCUG for patients with abnormal DMSA and/or recurrent FUTI. Copyright © 2015 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
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Seuss, Hannes; Dankerl, Peter; Cavallaro, Alexander; Uder, Michael; Hammon, Matthias
2016-05-20
To evaluate screening and diagnostic accuracy for the detection of osteoblastic rib lesions using an advanced post-processing package enabling in-plane rib reading in CT-images. We retrospectively assessed the CT-data of 60 consecutive prostate cancer patients by applying dedicated software enabling in-plane rib reading. Reading the conventional multiplanar reconstructions was considered to be the reference standard. To simulate clinical practice, the reader was given 10 s to screen for sclerotic rib lesions in each patient applying both approaches. Afterwards, every rib was evaluated individually with both approaches without a time limit. Sensitivities, specificities, positive/negative predictive values and the time needed for detection were calculated depending on the lesion's size (largest diameter < 5 mm, 5-10 mm, > 10 mm). In 53 of 60 patients, all ribs were properly displayed in plane, in five patients ribs were partially displayed correctly, and in two patients none of the ribs were displayed correctly. During the 10-s screening approach all patients with sclerotic rib lesions were correctly identified reading the in-plane images (including the patients without a correct rib segmentation), whereas 14 of 23 patients were correctly identified reading conventional multiplanar images. Overall screening sensitivity, specificity, and positive/negative predictive values were 100/27.0/46.0/100 %, respectively, for in-plane reading and 60.9/100/100/80.4 %, respectively, for multiplanar reading. Overall diagnostic (no time limit) sensitivity, specificity, and positive/negative predictive values of in-plane reading were 97.8/92.8/74.6/99.5 %, respectively. False positive results predominantly occurred for lesions <5 mm in size. In-plane reading of the ribs allows reliable detection of osteoblastic lesions for screening purposes. The limited specificity results from false positives predominantly occurring for small lesions.
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Mir, Nuria; Sánchez, Miguel; Baquero, Fernando; López, Blanca; Calderón, Celia; Cantón, Rafael
1998-01-01
The early detection of colonization with methicillin-resistant Staphylococcus aureus (MRSA) of patients in intensive-care units is an essential step in the strategy for preventing MRSA epidemics. In this study, tubes containing soft salt-mannitol agar with cloxacillin (6 μg/ml) (SSMAC) were prepared for inoculation of clinical samples at patients’ bedsides by personnel of an intensive-care unit. A total of 1,914 swabs from different sample sites of 81 patients were dipped into SSMAC tubes, and after 24 h of incubation (in an incubator located near the intensive-care unit), an evident color change was considered by the intensive-care-unit personnel to be an MRSA alarm. Sixty-three (3.3%) SSMAC tubes were considered positive for MRSA, 1,827 (95.4%) were considered negative, and 24 (1.2%) were considered intermediate. Compared with values for parallel conventional surveillance cultures for MRSA, excluding tubes with intermediate results, the SSMAC test had a sensitivity of 72.7%, a specificity of 99.2%, a positive predictive value of 76.2%, and a negative predictive value of 99.0%. When intermediate tubes were considered positive, the corresponding values were 75.3, 98.2, 63.2, and 99.0%, respectively. The sensitivity and specificity values of the test to identify MRSA-colonized patients were 89.4 and 100%, respectively. Oropharyngeal and naris specimens were the most reliable samples for MRSA detection. False-negative results were frequent in bronchial aspirates with low (<103 to 106 CFU/ml) MRSA counts. False-positive results were mainly due to methicillin-resistant Staphylococcus haemolyticus. The SSMAC tube is a useful, rapid, and inexpensive tool for the early identification of MRSA-colonized patients and, consequently, for the implementation of measures to prevent the spread of MRSA. PMID:9542922
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2014-01-01
Background This study aimed to better understand the supporting role that mutational profiling (MP) of DNA from microdissected cytology slides and supernatant specimens may play in the diagnosis of malignancy in fine-needle aspirates (FNA) and biliary brushing specimens from patients with pancreaticobiliary masses. Methods Cytology results were examined in a total of 30 patients with associated surgical (10) or clinical (20) outcomes. MP of DNA from microdissected cytology slides and from discarded supernatant fluid was analyzed in 26 patients with atypical, negative or indeterminate cytology. Results Cytology correctly diagnosed aggressive disease in 4 patients. Cytological diagnoses for the remaining 26 were as follows: 16 negative (9 false negative), 9 atypical, 1 indeterminate. MP correctly determined aggressive disease in 1 false negative cytology case and confirmed a negative cytology diagnosis in 7 of 7 cases of non-aggressive disease. Of the 9 atypical cytology cases, MP correctly diagnosed 7 as positive and 1 as negative for aggressive disease. One specimen that was indeterminate by cytology was correctly diagnosed as non-aggressive by MP. When first line malignant (positive) cytology results were combined with positive second line MP results, 12/21 cases of aggressive disease were identified, compared to 4/21 cases identified by positive cytology alone. Conclusions When first line cytology results were uncertain (atypical), questionable (negative), or not possible (non-diagnostic/indeterminate), MP provided additional information regarding the presence of aggressive disease. When used in conjunction with first line cytology, MP increased detection of aggressive disease without compromising specificity in patients that were difficult to diagnose by cytology alone. PMID:25084836
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Evaluation of the Sysmex UF1000i flow cytometer for ruling out bacterial urinary tract infection.
De Rosa, Rita; Grosso, Shamanta; Bruschetta, Graziano; Avolio, Manuela; Stano, Paola; Modolo, Maria Luisa; Camporese, Alessandro
2010-08-05
Urine culture is one of the most frequently requested tests in microbiology, and it represents the gold standard for the diagnosis of UTIs. Considering the high prevalence of negative results and the long TAT of the culture test, the use of a rapid and reliable screening method is becoming more and more important, as it reduces the workload, the TAT of negative results, and above all, unnecessary antibiotic prescription. The Sysmex UF1000i is a new urine flow cytometry analyzer capable of quantifying urinary particles, including BACT, WBCs, and YLCs. To evaluate the analytical performance of the UF1000i as a method for ruling out UTIs, we examined 1349 urine samples and compared the UF1000i results with standard urine culture results. With instrument cut-off values of 170BACTx10(6)/L and 150WBCsx10(6)/L, we obtained a sensitivity of 98.8%, a specificity of 76.5%, a NPV of 99.5%, and four false negative results (1.2%), avoiding the culture of 57.1% of samples. The Sysmex UF1000i was capable of improving the efficiency of a routine microbiology laboratory by processing 100samples/h and providing negative results in a few minutes, thus reducing unnecessary testing with an acceptable number of false negative results. In addition, the preliminary evaluation of B_FSC and B_FLH parameters from bacteria histograms seems to be useful for the distinction of bacterial strains detected (Gram-negatives versus Gram-positives). In fact when B_FSC was less than 30 ch, it allowed the distinction of Gram-negative bacteria in 97% of the samples. Copyright 2010 Elsevier B.V. All rights reserved.
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Carrera, D; de la Flor, M; Galera, J; Amillano, K; Gomez, M; Izquierdo, V; Aguilar, E; López, S; Martínez, M; Martínez, S; Serra, J M; Pérez, M; Martin, L
2016-01-01
The aim of our study was to evaluate sentinel lymph node biopsy as a diagnostic test for assessing the presence of residual metastatic axillary lymph nodes after neoadjuvant chemotherapy, replacing the need for a lymphadenectomy in negative selective lymph node biopsy patients. A multicentre, diagnostic validation study was conducted in the province of Tarragona, on women with T1-T3, N1-N2 breast cancer, who presented with a complete axillary response after neoadjuvant chemotherapy. Study procedures consisted of performing an selective lymph node biopsy followed by lymphadenectomy. A total of 53 women were included in the study. Surgical detection rate was 90.5% (no sentinel node found in 5 patients). Histopathological analysis of the lymphadenectomy showed complete disease regression of axillary nodes in 35.4% (17/48) of the patients, and residual axillary node involvement in 64.6% (31/48) of them. In lymphadenectomy positive patients, 28 had a positive selective lymph node biopsy (true positive), while 3 had a negative selective lymph node biopsy (false negative). Of the 28 true selective lymph node biopsy positives, the sentinel node was the only positive node in 10 cases. All lymphadenectomy negative cases were selective lymph node biopsy negative. These data yield a sensitivity of 93.5%, a false negative rate of 9.7%, and a global test efficiency of 93.7%. Selective lymph node biopsy after chemotherapy in patients with a complete axillary response provides valid and reliable information regarding axillary status after neoadjuvant treatment, and might prevent lymphadenectomy in cases with negative selective lymph node biopsy. Copyright © 2016 Elsevier España, S.L.U. and SEMNIM. All rights reserved.
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Terakado, Shingo; Glass, Thomas R; Sasaki, Kazuhiro; Ohmura, Naoya
2014-01-01
A simple new model for estimating the screening performance (false positive and false negative rates) of a given test for a specific sample population is presented. The model is shown to give good results on a test population, and is used to estimate the performance on a sampled population. Using the model developed in conjunction with regulatory requirements and the relative costs of the confirmatory and screening tests allows evaluation of the screening test's utility in terms of cost savings. Testers can use the methods developed to estimate the utility of a screening program using available screening tests with their own sample populations.
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Clare, John; McKinney, Shawn T; DePue, John E; Loftin, Cynthia S
2017-10-01
It is common to use multiple field sampling methods when implementing wildlife surveys to compare method efficacy or cost efficiency, integrate distinct pieces of information provided by separate methods, or evaluate method-specific biases and misclassification error. Existing models that combine information from multiple field methods or sampling devices permit rigorous comparison of method-specific detection parameters, enable estimation of additional parameters such as false-positive detection probability, and improve occurrence or abundance estimates, but with the assumption that the separate sampling methods produce detections independently of one another. This assumption is tenuous if methods are paired or deployed in close proximity simultaneously, a common practice that reduces the additional effort required to implement multiple methods and reduces the risk that differences between method-specific detection parameters are confounded by other environmental factors. We develop occupancy and spatial capture-recapture models that permit covariance between the detections produced by different methods, use simulation to compare estimator performance of the new models to models assuming independence, and provide an empirical application based on American marten (Martes americana) surveys using paired remote cameras, hair catches, and snow tracking. Simulation results indicate existing models that assume that methods independently detect organisms produce biased parameter estimates and substantially understate estimate uncertainty when this assumption is violated, while our reformulated models are robust to either methodological independence or covariance. Empirical results suggested that remote cameras and snow tracking had comparable probability of detecting present martens, but that snow tracking also produced false-positive marten detections that could potentially substantially bias distribution estimates if not corrected for. Remote cameras detected marten individuals more readily than passive hair catches. Inability to photographically distinguish individual sex did not appear to induce negative bias in camera density estimates; instead, hair catches appeared to produce detection competition between individuals that may have been a source of negative bias. Our model reformulations broaden the range of circumstances in which analyses incorporating multiple sources of information can be robustly used, and our empirical results demonstrate that using multiple field-methods can enhance inferences regarding ecological parameters of interest and improve understanding of how reliably survey methods sample these parameters. © 2017 by the Ecological Society of America.
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Petruševska, Marija; Urleb, Uroš; Peternel, Luka
2013-11-01
The excipient-mediated precipitation inhibition is classically determined by the quantification of the dissolved compound in the solution. In this study, two alternative approaches were evaluated, one is the light scattering (nephelometer) and other is the turbidity (plate reader) microtiter plate-based methods which are based on the quantification of the compound precipitate. Following the optimization of the nephelometer settings (beam focus, laser gain) and the experimental conditions, the screening of 23 excipients on the precipitation inhibition of poorly soluble fenofibrate and dipyridamole was performed. The light scattering method resulted in excellent correlation (r>0.91) between the calculated precipitation inhibitor parameters (PIPs) and the precipitation inhibition index (PI(classical)) obtained by the classical approach for fenofibrate and dipyridamole. Among the evaluated PIPs AUC100 (nephelometer) resulted in only four false positives and lack of false negatives. In the case of the turbidity-based method a good correlation of the PI(classical) was obtained for the PIP maximal optical density (OD(max), r=0.91), however, only for fenofibrate. In the case of the OD(max) (plate reader) five false positives and two false negatives were identified. In conclusion, the light scattering-based method outperformed the turbidity-based one and could be reliably used for identification of novel precipitation inhibitors. Copyright © 2013 Elsevier B.V. All rights reserved.
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A Rapid, Presumptive Procedure for the Detection of Salmonella in Foods and Food Ingredients
Hoben, D. A.; Ashton, D. H.; Peterson, A. C.
1973-01-01
A rapid detection procedure was developed in which a lysine-iron-cystine-neutral red (LICNR) broth medium, originally described by Hargrove et al. in 1971, was modified and used to detect the presence of viable Salmonella organisms in a variety of foods, food ingredients, and feed materials by using a two-step enrichment technique. Tetrathionate broth was used to enrich samples with incubation at 41 C for 20 hr, followed by transfer to LICNR broth and incubation at 37 C for 24 hr for further enrichment and for the detection of Salmonella organisms by color change. One hundred ten samples representing 18 different sample types were evaluated for the presence of viable Salmonella. Ninety-four percent of the samples found to be presumptive positive by this method were confirmed as positive by a culture method. Fluorescent-antibody results also compared closely. A second study was conducted under quality-control laboratory conditions by using procedures currently employed for Salmonella detection. One hundred forty-three samples representing 19 different sample types were evaluated for the presence of viable Salmonella. No false negatives were observed with the rapid-detection method. The usefulness of the LICNR broth procedure as a screening technique to eliminate negative samples rapidly and to identify presumptive positive samples for the presence of viable Salmonella organisms was established in this laboratory. PMID:4568884
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Guntupalli, Kalpalatha K; Alapat, Philip M; Bandi, Venkata D; Kushnir, Igal
2008-12-01
Computerized lung-sound analysis is a sensitive and quantitative method to identify wheezing by its typical pattern on spectral analysis. We evaluated the accuracy of the VRI, a multi-sensor, computer-based device with an automated technique of wheeze detection. The method was validated in 100 sound files from seven subjects with asthma or chronic obstructive pulmonary disease and seven healthy subjects by comparison of auscultation findings, examination of audio files, and computer detection of wheezes. Three blinded physicians identified 40 sound files with wheezes and 60 sound files without wheezes. Sensitivity and specificity were 83% and 85%, respectively. Negative predictive value and positive predictive value were 89% and 79%, respectively. Overall inter-rater agreement was 84%. False positive cases were found to contain sounds that simulate wheezes, such as background noises with high frequencies or strong noises from the throat that could be heard and identified without a stethoscope. The present findings demonstrate that the wheeze detection algorithm has good accuracy, sensitivity, specificity, negative predictive value and positive predictive value for wheeze detection in regional analyses with a single sensor and multiple sensors. Results are similar to those reported in the literature. The device is user-friendly, requires minimal patient effort, and, distinct from other devices, it provides a dynamic image of breath sound distribution with wheeze detection output in less than 1 minute.
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Whitson, Bryan A; Groth, Shawn S; Odell, David D; Briones, Eleazar P; Maddaus, Michael A; D'Cunha, Jonathan; Andrade, Rafael S
2013-05-01
Mediastinal staging in patients with non-small cell lung cancer (NSCLC) with endobronchial ultrasound-guided fine-needle aspiration (EBUS-FNA) requires a high negative predictive value (NPV) (ie, low false negative rate). We provide a conservative calculation of NPV that calls for caution in the interpretation of EBUS results. We retrospectively analyzed our prospectively gathered database (January 2007 to November 2011) to include NSCLC patients who underwent EBUS-FNA for mediastinal staging. We excluded patients with metastatic NSCLC and other malignancies. We assessed FNAs with rapid on-site evaluation (ROSE). The calculation of NPV is NPV = true negatives/true negatives + false negatives. However, this definition ignores nondiagnostic samples. Nondiagnostic samples should be added to the NPV denominator because decisions based on nondiagnostic samples could be flawed. We conservatively calculated NPV for EBUS-FNA as NPV = true negatives/true negatives + false negatives + nondiagnostic. We defined false negatives as negative FNAs but NSCLC-positive surgical biopsy of the same site. Nondiagnostic FNAs were nonrepresentative of lymphoid tissue. We compared diagnostic performance with the inclusion and exclusion of nondiagnostic procedures. We studied 120 patients with NSCLC who underwent EBUS-FNA; 5 patients had false negative findings and 10 additional patients had nondiagnostic results. The NPV with and without inclusion of nondiagnostic samples was 65.9% and 85.3%, respectively. The inclusion of nondiagnostic specimens into the conservative, worst-case-scenario calculation of NPV for EBUS-FNA in NSCLC lowers the NPV from 85.3% to 65.9%. The true NPV is likely higher than 65.9% as few nondiagnostic specimens are false negatives. Caution is imperative for the safe application of EBUS-FNA in NSCLC staging. Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.
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Marucci, Gianluca; Pezzotti, Patrizio; Pozio, Edoardo
2009-02-23
To control Trichinella spp. infection in the European Union, all slaughtered pigs should be tested by one of the approved digestion methods described in EU directive 2075/2005. The aim of the present work was to evaluate, by a ring trial, the sensitivity of the digestion method used at the National Reference Laboratories for Parasites (NRLP). These Laboratories are responsible for the quality of the detection method in their own country. Of the 27 EU countries, only three (Hungary, Luxembourg and Malta) did not participate in the ring trial. Each participating laboratory received 10 samples of 100g of minced pork containing 3-5 larvae (3 samples), 10-20 larvae (3 samples), 30-50 larvae (3 samples), and one negative control. In each positive sample, there were living Trichinella spiralis larvae without the collagen capsule, obtained by partial artificial digestion of muscle tissue from infected mice. No false positive sample was found in any laboratories, whereas nine laboratories (37.5%) failed to detect some positive samples with the percentage of false negatives ranging from 11 to 100%. The variation between expected and reported larval counts observed among the participating laboratories was statistically significant. There was a direct correlation between the consistency of the results and the use of a validated/accredited digestion method. Conversely, there was no correlation between the consistency of the results and the number of digestions performed yearly by the NRLP. These results support the importance of validating the test.
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Badoud, F; Grata, E; Perrenoud, L; Avois, L; Saugy, M; Rudaz, S; Veuthey, J-L
2009-05-15
The general strategy to perform anti-doping analyses of urine samples starts with the screening for a wide range of compounds. This step should be fast, generic and able to detect any sample that may contain a prohibited substance while avoiding false negatives and reducing false positive results. The experiments presented in this work were based on ultra-high-pressure liquid chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry. Thanks to the high sensitivity of the method, urine samples could be diluted 2-fold prior to injection. One hundred and three forbidden substances from various classes (such as stimulants, diuretics, narcotics, anti-estrogens) were analysed on a C(18) reversed-phase column in two gradients of 9min (including two 3min equilibration periods) for positive and negative electrospray ionisation and detected in the MS full scan mode. The automatic identification of analytes was based on retention time and mass accuracy, with an automated tool for peak picking. The method was validated according to the International Standard for Laboratories described in the World Anti-Doping Code and was selective enough to comply with the World Anti-Doping Agency recommendations. In addition, the matrix effect on MS response was measured on all investigated analytes spiked in urine samples. The limits of detection ranged from 1 to 500ng/mL, allowing the identification of all tested compounds in urine. When a sample was reported positive during the screening, a fast additional pre-confirmatory step was performed to reduce the number of confirmatory analyses.
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Development of a one-step duplex RT-qPCR for the quantification of phocine distemper virus.
Bogomolni, Andrea L; Frasca, Salvatore; Matassa, Keith A; Nielsen, Ole; Rogers, Kara; De Guise, Sylvain
2015-04-01
Worldwide, stranded marine mammals and the network personnel who respond to marine mammal mortality have provided much of the information regarding marine morbillivirus infections. An assay to determine the amount of virus present in tissue samples would be useful to assist in routine surveying of animal health and for monitoring large-scale die-off events. False negatives from poor-quality samples prevent determination of the true extent of infection, while only small amounts of tissue samples or archived RNA may be available at the time of collection for future retrospective analysis. We developed a one-step duplex real-time reverse transcriptase-quantitative-PCR assay (RT-qPCR) based on Taqman probe technology to quantify phocine distemper virus (PDV) isolated from an outbreak in harbor (Phoca vitulina concolor) and gray seals (Halichoerus grypus) along the northeast US coast in 2006. The glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) gene was selected to assess RNA quality. This duplex assay is specific for PDV and sensitive through a range of 10(0) to 10(9) copies ds-plasmid DNA. For the GAPDH target, the reaction in duplex amplified 10(0) to 10(9) copies of ds-plasmid DNA and was detectable in multiple seal species. This assay reduced the likelihood of false negative results due to degradation of tissues and well-to-well variability while providing sensitive and specific detection of PDV, which would be applicable in molecular epidemiologic studies and pathogen detection in field and laboratory investigations involving a variety of seal species.
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Muthukumar, Alagarraju; Alatoom, Adnan; Burns, Susan; Ashmore, Jerry; Kim, Anne; Emerson, Brian; Bannister, Edward; Ansari, M Qasim
2015-01-01
To assess the false-positive and false-negative rates of a 4th-generation human immunodeficiency virus (HIV) assay, the Abbott ARCHITECT, vs 2 HIV 3rd-generation assays, the Siemens Centaur and the Ortho-Clinical Diagnostics Vitros. We examined 123 patient specimens. In the first phase of the study, we compared 99 specimens that had a positive screening result via the 3rd-generation Vitros assay (10 positive, 82 negative, and 7 indeterminate via confirmatory immunofluorescent assay [IFA]/Western blot [WB] testing). In the second phase, we assessed 24 HIV-1 RNA-positive (positive result via the nuclear acid amplification test [NAAT] and negative/indeterminate results via the WB test) specimens harboring acute HIV infection. The 4th-generation ARCHITECT assay yielded fewer false-positive results (n = 2) than the 3rd-generation Centaur (n = 9; P = .02) and Vitros (n = 82; P <.001) assays. One confirmed positive case had a false-negative result via the Centaur assay. When specimens from the 24 patients with acute HIV-1 infection were tested, the ARCHITECT assay yielded fewer false-negative results (n = 5) than the Centaur (n = 10) (P = .13) and the other 3rd-generation tests (n = 16) (P = .002). This study indicates that the 4th-generation ARCHITECT HIV assay yields fewer false-positive and false-negative results than the 3rd-generation HIV assays we tested. Copyright© by the American Society for Clinical Pathology (ASCP).
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Yong, Dongeun; Lee, Yangsoon; Jeong, Seok Hoon; Lee, Kyungwon
2012-01-01
Accurate detection of metallo-β-lactamase (MBL)-producing Pseudomonas spp. and Acinetobacter spp. became very important with the increasing prevalence of carbapenem-nonsusceptible clinical isolates. The performance of phenotypic MBL detection methods may depend on the types of MBL and the characteristics of the isolates. A high false-positive rate is a problem with EDTA-based MBL detection methods. We evaluated the performance of double-disk potentiation tests (DDPTs) and disk potentiation tests (DPTs) with dipicolinic acid (DPA) using 44 isolates of Pseudomonas spp. and Acinetobacter spp. producing IMP-1-like, VIM-2-like, and SIM-1 type MBLs. Also, we characterized P. aeruginosa isolates with positive imipenem (IPM)-DPA DDPT, but negative meropenem (MEM)-DPA DDPT, and determined possibility of improving a DDPT by using MacConkey agar. Among five different DDPT methods, the IPM-DPA 250-μg method showed the highest sensitivity (97.7%) and specificity (100%). Among four DPT tests, the highest sensitivity (100%) was shown by the IPM-EDTA 1,900-μg disk method, but the specificity was very low (11.4%). Five of six P. aeruginosa isolates with false-negative DDPTs with MEM-DPA 250-μg disks carried blaIMP-6, and the high level resistance to MEM (MIC ≥ 512 μg/ml) was reduced by the presence of phenylalanine arginine β-naphtylamide. Improvement of DDPTs was observed when MacConkey agar was used instead of Mueller-Hinton agar. In conclusion, DPA is a better MBL inhibitor than EDTA for detection of Pseudomonas spp. and Acinetobacter spp. with IMP-1-like, VIM-2-like, and SIM-1-type MBLs. In DPA DDPTs, IPM disks perform better than MEM disks when the isolates are highly resistant to MEM due to the overexpression of efflux pumps. PMID:22837321
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Review: Diagnostic accuracy of PCR-based detection tests for Helicobacter Pylori in stool samples.
Khadangi, Fatemeh; Yassi, Maryam; Kerachian, Mohammad Amin
2017-12-01
Although different methods have been established to detect Helicobacter pylori (H. pylori) infection, identifying infected patients is an ongoing challenge. The aim of this meta-analysis was to provide pooled diagnostic accuracy measures for stool PCR test in the diagnosis of H. pylori infection. In this study, a systematic review and meta-analysis were carried out on various sources, including MEDLINE, Web of Sciences, and the Cochrane Library from April 1, 1999, to May 1, 2016. This meta-analysis adheres to the guidelines provided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses report (PRISMA Statement). The clinical value of DNA stool PCR test was based on the pooled false positive, false negative, true positive, and true negative of different genes. Twenty-six of 328 studies identified met the eligibility criteria. Stool PCR test had a performance of 71% (95% CI: 68-73) sensitivity, 96% (95% CI: 94-97) specificity, and 65.6 (95% CI: 30.2-142.5) diagnostic odds ratio (DOR) in diagnosis of H. pylori. The DOR of genes which showed the highest performance of stool PCR tests was as follows: 23S rRNA 152.5 (95% CI: 55.5-418.9), 16S rRNA 67.9 (95%CI: 6.4-714.3), and glmM 68.1 (95%CI: 20.1-231.7). The sensitivity and specificity of stool PCR test are relatively in the same spectrum of other diagnostic methods for the detection of H. pylori infection. In descending order of significance, the most diagnostic candidate genes using PCR detection were 23S rRNA, 16S rRNA, and glmM. PCR for 23S rRNA gene which has the highest performance could be applicable to detect H. pylori infection. © 2017 John Wiley & Sons Ltd.
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How does negative emotion cause false memories?
Brainerd, C J; Stein, L M; Silveira, R A; Rohenkohl, G; Reyna, V F
2008-09-01
Remembering negative events can stimulate high levels of false memory, relative to remembering neutral events. In experiments in which the emotional valence of encoded materials was manipulated with their arousal levels controlled, valence produced a continuum of memory falsification. Falsification was highest for negative materials, intermediate for neutral materials, and lowest for positive materials. Conjoint-recognition analysis produced a simple process-level explanation: As one progresses from positive to neutral to negative valence, false memory increases because (a) the perceived meaning resemblance between false and true items increases and (b) subjects are less able to use verbatim memories of true items to suppress errors.
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Issa, Amalia M; Tufail, Waqas; Atehortua, Nelson; McKeever, John
2013-05-01
Molecular diagnostics are increasingly being used to help guide decision-making for personalized medical treatment of breast and colorectal cancer patients. The main aim of this study was to better understand and determine breast and colorectal cancer patients' decision-making strategies and the trade-offs they make in deciding about characteristics of molecular genomic diagnostics for breast and colorectal cancer. We surveyed a nationally representative sample of 300 breast and colorectal cancer patients using a previously developed web-administered instrument. Eligibility criteria included patients aged 18 years and older with either breast or colorectal cancer. We explored several attributes and attribute levels of molecular genomic diagnostics in 20 scenarios. Our analysis revealed that both breast and colorectal cancer patients weighted the capability of molecular genomic diagnostics to determine the probability of treatment efficacy as being of greater importance than information provided to detect adverse events. The probability of either false-positive or -negative results was ranked highly as a potential barrier by both breast and colorectal patients. However, 78.6% of breast cancer patients ranked the possibility of a 'false-negative test result leading to undertreatment' higher than the 'chance of a false positive, which may lead to overtreatment' (68%). This finding contrasted with the views of colorectal cancer patients who ranked the chance of a false positive as being of greater concern than a false negative (72.8 vs 63%). Overall, cancer patients exhibited a high willingness to accept and pay for genomic diagnostic tests, especially among breast cancer patients. Cancer patients seek a test accuracy rate of 90% or higher. Breast and colorectal cancer patients' decisions about genomic diagnostics are influenced more by the probability of being cured than by avoiding potential severe adverse events. This study provides insights into the relative weight that breast and colorectal cancer patients place on various aspects of molecular genomic diagnostics, and the trade-offs they are willing to make among attributes of such tests.
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Parodi, S; Balbi, C; Taningher, M; Pala, M; Russo, P; Abelmoschi, M L; Santi, L
1982-11-01
DNA damage induced in vivo by 3'-methyl-4-dimethylaminoazobenzene (3'CH3DAB) was investigated with 2 differently sensitive techniques: the alkaline elution assay and the viscometric measurement of DNA damage. 3'CH3DAB appeared to be falsely negative with the alkaline elution assay, whereas with the viscometric approach, which is about 30-50 times more sensitive, it appeared positive, and the DNA damage was dose-dependent.
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Influence of furosemide on the detection of flunixin meglumine in horse urine samples.
Araújo, A C; Salvadori, M C; Velletri, M E; Camargo, M M
1990-01-01
The possibility of false negative results from TLC when a diuretic is administered concomitantly with flunixin was studied. Samples were subjected to solvent extraction from acidic aqueous solutions; duplicate samples were also subjected to alkaline hydrolysis at pH 12.5. The internal standard was flufenamic acid. The quantification of flunixin was performed by HPLC and the results confirmed by GC/MS. The data show that furosemide influences the urinary concentration of flunixin.
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Is there a positive bias in false recognition? Evidence from confabulating amnesia patients.
Alkathiri, Nura H; Morris, Robin G; Kopelman, Michael D
2015-10-01
Although there is some evidence for a positive emotional bias in the content of confabulations in brain damaged patients, findings have been inconsistent. The present study used the semantic-associates procedure to induce false recall and false recognition in order to examine whether a positive bias would be found in confabulating amnesic patients, relative to non-confabulating amnesic patients and healthy controls. Lists of positive, negative and neutral words were presented in order to induce false recall or false recognition of non-presented (but semantically associated) words. The latter were termed 'critical intrusions'. Thirteen confabulating amnesic patients, 13 non-confabulating amnesic patients and 13 healthy controls were investigated. Confabulating patients falsely recognised a higher proportion of positive (but unrelated) words, compared with non-confabulating patients and healthy controls. No differences were found for recall memory. Signal detection analysis, however, indicated that the positive bias for false recognition memory might reflect weaker memory in the confabulating amnesic group. This suggested that amnesia patients with weaker memory are more likely to confabulate and the content of these confabulations are more likely to be positive. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Ginocchio, C. C.; Barth, D.; Zhang, F.
2008-01-01
This study compared the clinical performance of the Digene Hybrid Capture 2 (HC2) assay to that of a prototype Third Wave Invader human papillomavirus (HPV) (IHPV) analyte-specific reagent-based assay for the detection of oncogenic or “high-risk” (HR) HPV DNA using liquid-based cytology specimens. In total, 821 ThinPrep vials were tested using both assays. In accordance with the type-specific probes contained within each test, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for the IHPV assay were 95.9%, 97.6%, 97.5%, and 96.1%, respectively, and those for the HC2 assay were 98.1%, 86.2%, 87.1%, and 97.9%. Overall, the sensitivity and NPV were comparable between the assays, but the IHPV assay demonstrated a better specificity and PPV, since the IHPV assay had fewer false-positive HR HPV results. The incorporation of an internal control to evaluate the cellularity of the test material is an important feature of the IHPV assay and should reduce the risk of false-negative results due to insufficient sample collection rather than the lack of HR HPV DNA. An additional benefit of the IHPV assay was the smaller sample volume required (1 ml versus 4 ml for the HC2 assay). PMID:18367578
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The Diagnostic Value of Routine Contrast Esophagram in Anastomotic Leaks After Esophagectomy.
Hu, Zhongwu; Wang, Xiaowe; An, Xush; Li, Wenjin; Feng, Yun; You, Zhenbing
2017-08-01
Routine contrast esophagram has been shown to be increasingly limited in diagnosing anastomotic leaks after esophagectomy. Patients undergoing esophagectomy from 2013 to 2014 at Huai'an First Peoples' Hospital were identified. We retrospectively analyzed patients who underwent routine contrast esophagram on postoperative day 7 (range 6-10) to preclude anastomotic leaks after esophagectomy. In 846 patients who underwent esophagectomy, a cervical anastomosis was performed in 286 patients and an intrathoracic anastomosis in 560 patients. There were 57 (6.73%) cases with anastomotic leaks, including cervical leaks in 36 and intrathoracic leaks in 21 patients. In the cervical anastomotic leak patients, 13 were diagnosed by early local clinical symptoms and 23 underwent routine contrast esophagram. There were 7 (30.4%) true-positive, 11 (47.8%) false-negative, and five (21.8%) equivocal cases. In the intrathoracic anastomotic leak patients, four (19%) were diagnosed by clinical symptoms, 16 (76.2%) were true positives, and one (4.8%) was a false negative. Aspiration occurred in five patients with cervical anastomoses and in eight patients with intrathoracic anastomoses; aspiration pneumonitis did not occur in these cases. Gastrografin and barium are safe contrast agents to use in post-esophagectomy contrast esophagram. Because of the low sensitivity in detecting cervical anastomotic leaks, routine contrast esophagram is not advised. For patients with intrathoracic anastomoses, it is still an effective method for detecting anastomotic leaks.
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Abdulmawjood, A; Roth, S; Bülte, M
2002-10-01
For the detection of food born bacteria by polymerase chain reaction (PCR) in food products, an internal amplification control (IAC) is required in order to prevent false negative results that might be caused by PCR inhibitors. In the present study, two IACs were constructed using two different methods. These IACs were designed in a way that the same primer pair can be used to amplify the target DNA and coamplify the IAC. The first IAC with a size of approximately 200 bp was constructed by deleting a part of the amplicon of the original target DNA (500 bp) between the two primer sites to produce an IAC smaller than the target DNA. The second IAC with a size of approximately 600 bp was synthesized in a one step PCR reaction. The primers used in this reaction possessed 5' over-hanging ends, which were identical to the primers used in the diagnostic reaction, whereas their 3' ends were complementary to the (pUC19) predetermined DNA sequence of defined length and sequence. The concentration of IACs appeared to be critical. Too much IAC DNA template would out-compete the target DNA template, thus giving a false negative result. However the use of an optimal IAC concentration increased the reliability of the PCR assays and appeared to be useful for food diagnostics.
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Hutchison, J R; Piepel, G F; Amidan, B G; Hess, B M; Sydor, M A; Deatherage Kaiser, B L
2018-05-01
We evaluated the effects of Bacillus anthracis surrogates, low surface concentrations, surface materials and assay methods on false-negative rate (FNR) and limit of detection (LOD 95 ) for recovering Bacillus spores using a macrofoam-swab sampling procedure. Bacillus anthracis Sterne or Bacillus atrophaeus Nakamura spores were deposited over a range of low target concentrations (2-500 per coupon) onto glass, stainless steel, vinyl tile and plastic. Samples were assayed using a modified Rapid Viability-PCR (mRV-PCR) method and the traditional plate culture method to obtain FNR and LOD 95 results. Mean FNRs tended to be lower for mRV-PCR compared to culturing, and increased as spore concentration decreased for all surface materials. Surface material, but not B. anthracis surrogate, influenced FNRs with the mRV-PCR method. The mRV-PCR LOD 95 was lowest for glass and highest for vinyl tile. LOD 95 values overall were lower for mRV-PCR than for the culture method. This study adds to the limited data on FNR and LOD 95 for mRV-PCR and culturing methods with low concentrations of B. anthracis sampled from various surface materials by the CDC macrofoam-swab method. These are key inputs for planning characterization and clearance studies for low contamination levels of B. anthracis. © 2018 The Society for Applied Microbiology.
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Bohaychuk, Valerie M; Gensler, Gary E; King, Robin K; Wu, John T; McMullen, Lynn M
2005-12-01
Rapid and molecular technologies such as enzyme-linked immunosorbent assay (ELISA), PCR, and lateral flow immunoprecipitation can reduce the time and labor involved in screening food products for the presence of pathogens. These technologies were compared with conventional culture methodology for the detection of Salmonella, Campylobacter, Listeria, and Escherichia coli O157:H7 inoculated in raw and processed meat and poultry products. Recommended protocols were modified so that the same enrichment broths used in the culture methods were also used in the ELISA, PCR, and lateral flow immunoprecipitation assays. The percent agreement between the rapid technologies and culture methods ranged from 80 to 100% depending on the pathogen detected and the method used. ELISA, PCR, and lateral flow immunoprecipitation all performed well, with no statistical difference, compared with the culture method for the detection of E. coli O157:H7. ELISA performed better for the detection of Salmonella, with sensitivity and specificity rates of 100%. PCR performed better for the detection of Campylobacter jejuni, with 100% agreement to the culture method. PCR was highly sensitive for the detection of all the foodborne pathogens tested except Listeria monocytogenes. Although the lateral flow immunoprecipitation tests were statistically different from the culture methods for Salmonella and Listeria because of false-positive results, the tests did not produce any false negatives, indicating that this method would be suitable for screening meat and poultry products for these pathogens.
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CRIM-TRACK: sensor system for detection of criminal chemical substances
NASA Astrophysics Data System (ADS)
Munk, Jens K.; Buus, Ole T.; Larsen, Jan; Dossi, Eleftheria; Tatlow, Sol; Lässig, Lina; Sandström, Lars; Jakobsen, Mogens H.
2015-10-01
Detection of illegal compounds requires a reliable, selective and sensitive detection device. The successful device features automated target acquisition, identification and signal processing. It is portable, fast, user friendly, sensitive, specific, and cost efficient. LEAs are in need of such technology. CRIM-TRACK is developing a sensing device based on these requirements. We engage highly skilled specialists from research institutions, industry, SMEs and LEAs and rely on a team of end users to benefit maximally from our prototypes. Currently we can detect minute quantities of drugs, explosives and precursors thereof in laboratory settings. Using colorimetric technology we have developed prototypes that employ disposable sensing chips. Ease of operation and intuitive sensor response are highly prioritized features that we implement as we gather data to feed into machine learning. With machine learning our ability to detect threat compounds amidst harmless substances improves. Different end users prefer their equipment optimized for their specific field. In an explosives-detecting scenario, the end user may prefer false positives over false negatives, while the opposite may be true in a drug-detecting scenario. Such decisions will be programmed to match user preference. Sensor output can be as detailed as the sensor allows. The user can be informed of the statistics behind the detection, identities of all detected substances, and quantities thereof. The response can also be simplified to "yes" vs. "no". The technology under development in CRIM-TRACK will provide custom officers, police and other authorities with an effective tool to control trafficking of illegal drugs and drug precursors.
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Delport, Johannes Andries; Mohorovic, Ivor; Burn, Sandi; McCormick, John Kenneth; Schaus, David; Lannigan, Robert; John, Michael
2016-07-01
Meticillin-resistant Staphylococcus aureus (MRSA) bloodstream infection is responsible for significant morbidity, with mortality rates as high as 60 % if not treated appropriately. We describe a rapid method to detect MRSA in blood cultures using a combined three-hour short-incubation BRUKER matrix-assisted laser desorption/ionization time-of-flight MS BioTyper protocol and a qualitative immunochromatographic assay, the Alere Culture Colony Test PBP2a detection test. We compared this combined method with a molecular method detecting the nuc and mecA genes currently performed in our laboratory. One hundred and seventeen S. aureus blood cultures were tested of which 35 were MRSA and 82 were meticillin-sensitive S. aureus (MSSA). The rapid combined test correctly identified 100 % (82/82) of the MSSA and 85.7 % (30/35) of the MRSA after 3 h. There were five false negative results where the isolates were correctly identified as S. aureus, but PBP2a was not detected by the Culture Colony Test. The combined method has a sensitivity of 87.5 %, specificity of 100 %, a positive predictive value of 100 % and a negative predictive value of 94.3 % with the prevalence of MRSA in our S. aureus blood cultures. The combined rapid method offers a significant benefit to early detection of MRSA in positive blood cultures.
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Hu, Shuangfang; Yu, Yigang; Li, Rong; Wu, Xinwei; Xiao, Xinglong; Wu, Hui
2016-03-01
Cronobacter sakazakii is a severe virulent strain that is frequently detected in powdered infant formula (PIF). Therefore, it is necessary to develop a fast and specific detection method. The specificity of our newly developed quantitative real-time PCR (qRT-PCR) was validated with DNA from 46 strains. Among them, 12 C. sakazakii strains were correctly amplified, whereas no positive florescent signal was observed from 34 nontarget controls. The detection limit of C. sakazakii was about 110 CFU/mL in broth and 1100 CFU/g in PIF. After enrichment in buffered peptone water for 6 h, our developed qRT-PCR assay could reliably detect C. sakazakii when the inoculation level was as low as 2 CFU/25 g (0.08 CFU/g) in PIF. The growth of C. sakazakii could be inhibited by the presence of Lactobacillus pentosus and Bacillus cereus, which used a longer enrichment period before the isolation was accomplished. However, at 5 and 50 CFU/25 g inoculation levels of C. sakazakii in the presence of 4 × 10(6) CFU L. pentosus/25 g or of 2 × 10(4) CFU B. cereus/25 g, the qRT-PCR assay could detect the presence of Cronobacter even though these artificially spiked samples were negative in culture. Therefore, our results indicated that the qRT-PCR assay could detect samples containing inhibitors and could avoid false negatives by using an internal amplification control.
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Papadia, Andrea; Gasparri, Maria Luisa; Radan, Anda P; Stämpfli, Chantal A L; Rau, Tilman T; Mueller, Michael D
2018-04-24
To evaluate the sensitivity, negative predictive value (NPV) and false-negative (FN) rate of the near infrared (NIR) indocyanine green (ICG) sentinel lymph node (SLN) mapping in patients with poorly differentiated endometrial cancer who have undergone a full pelvic and para-aortic lymphadenectomy after SLN mapping. We performed a retrospective analysis of patients with endometrial cancer undergoing a laparoscopic NIR-ICG SLN mapping followed by a systematic pelvic and para-aortic lymphadenectomy. Inclusion criteria were a grade 3 endometrial cancer or a high-risk histology (papillary serous, clear cell carcinoma, carcinosarcoma, and neuroendocrine carcinoma) and a completion pelvic and para-aortic lymphadenectomy to the renal vessels after SLN mapping. Overall and bilateral detection rates, sensitivity, NPV, and FN rates were calculated. From December 2012 until January 2017, 42 patients fulfilled inclusion criteria. Overall and bilateral detection rates were 100 and 90.5%, respectively. Overall, 23.8% of the patients had lymph node metastases. In one patient, despite negative bilateral pelvic SLNs, a metastatic non-SLN-isolated para-aortic metastasis was detected. This NSLN was clinically suspicious and sent to frozen section analysis during the surgery. FN rate, sensitivity, and NPV were 10, 90, and 97.1%, respectively. For the SLN mapping algorithm, FN rate, sensitivity, and NPV were 0, 100, and 100%, respectively. Laparoscopic NIR-ICG SLN mapping in high-risk endometrial cancer patients has acceptable sensitivity, FN rate, and NPV.
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Radiographic clearance of blunt cervical spine injury: plain radiograph or computed tomography scan?
Griffen, Margaret M; Frykberg, Eric R; Kerwin, Andrew J; Schinco, Miren A; Tepas, Joseph J; Rowe, Kathleen; Abboud, Jennifer
2003-08-01
The purpose of this study was to evaluate the roles of cervical spine radiographs (CSR) and computed tomography of the cervical spine (CTC) in the exclusion of cervical spine injury for adult blunt trauma patients. At the authors' institution, all adult blunt trauma patients with physical findings of posterior midline neck tenderness, altered mental status, or neurologic deficit are considered at risk of cervical spine injury and undergo both CSR and CTC for evaluation of the cervical spine. The TRACS database at level 1 of the trauma center at this institution was queried for all blunt trauma patients from November 2000 to October 2001. Patient injury severity score (ISS), Glascow Coma Score (GCS), age, gender, CSR results, CTC results, and treatment data were analyzed. The review included 3,018 blunt trauma patients with appropriate data. For 1,199 of these patients (779 men and 420 women) (40%) at risk for cervical spine injury, both CSR and CTC were performed for cervical spine evaluation. The average age of these patients was 39.4 years (range, 18-89 years). The average GCS was 13 and the average ISS was 8.4 in this study population. In 116 (9.5%) of these patients, a cervical spine injury (fracture or subluxation) was detected. The injury was identified on both CSR and CTC in 75 of these patients. In the remaining 41 patients (3.2%), the CSR results were negative, but injury was detected by CTC. All these injuries missed by CSR required treatment. For this group with false-negative CSR, the average GCS was 12 and the average ISS was 14.6. There were no missed cervical spine injuries among the patients with negative CTC results. No identifiable factors predicted false-negative CSR. There does not appear to be any role for CSR screening in this setting. The data from this study add to the growing body of evidence that CTC should replace CSR for the evaluation of the cervical spine in blunt trauma.
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Smuk, Gábor; Tornóczky, Tamás; Pajor, László; Chudoba, Ilse; Kajtár, Béla; Sárosi, Veronika; Pajor, Gábor
2018-05-19
EML4-ALK gene fusion (inv2(p21p23)) of non-small cell lung cancer (NSCLC) predisposes to tyrosine kinase inhibitor treatment. One of the gold standard diagnostics is the dual color (DC) break-apart (BA) FISH technique, however, the unusual closeness of the involved genes has been suggested to raise likelihood of random co-localization (RCL) of signals. Although this is suspected to decrease sensitivity (often to as low as 40-70%), the exact level and effect of RCL has not been revealed thus far. Signal distances were analyzed to the 0.1 µm precision in more than 25,000 nuclei, via automated high content-image cytometry. Negative and positive controls were created using conventional DC BA-, and inv2(p21p23) mimicking probe-sets, respectively. Average distance between red and green signals was 9.72 pixels (px) (±5.14px) and 3.28px (±2.44px), in positives and negatives, respectively; overlap in distribution being 41%. Specificity and sensitivity of correctly determining ALK status was 97% and 29%, respectively. When investigating inv2(p21p23) with DC BA FISH, specificity is high, but seven out of ten aberrant nuclei are inevitably falsely classified as negative, due to the extreme level of RCL. Together with genetic heterogeneity and dilution effect of non-tumor cells in NSCLC, this immense analytical false negativity is the primary cause behind the often described low diagnostic sensitivity. These results convincingly suggest that if FISH is to remain a gold standard for detecting the therapy relevant inv(2), either a modified evaluation protocol, or a more reliable probe-design should be considered than the current DC BA one. © 2018 International Society for Advancement of Cytometry. © 2018 International Society for Advancement of Cytometry.
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Detection of masses in mammogram images using CNN, geostatistic functions and SVM.
Sampaio, Wener Borges; Diniz, Edgar Moraes; Silva, Aristófanes Corrêa; de Paiva, Anselmo Cardoso; Gattass, Marcelo
2011-08-01
Breast cancer occurs with high frequency among the world's population and its effects impact the patients' perception of their own sexuality and their very personal image. This work presents a computational methodology that helps specialists detect breast masses in mammogram images. The first stage of the methodology aims to improve the mammogram image. This stage consists in removing objects outside the breast, reducing noise and highlighting the internal structures of the breast. Next, cellular neural networks are used to segment the regions that might contain masses. These regions have their shapes analyzed through shape descriptors (eccentricity, circularity, density, circular disproportion and circular density) and their textures analyzed through geostatistic functions (Ripley's K function and Moran's and Geary's indexes). Support vector machines are used to classify the candidate regions as masses or non-masses, with sensitivity of 80%, rates of 0.84 false positives per image and 0.2 false negatives per image, and an area under the ROC curve of 0.87. Copyright © 2011 Elsevier Ltd. All rights reserved.
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Definitive diagnosis of breast implant rupture using magnetic resonance imaging.
Ahn, C Y; Shaw, W W; Narayanan, K; Gorczyca, D P; Sinha, S; Debruhl, N D; Bassett, L W
1993-09-01
Breast implant rupture is an important complication of augmented and reconstructed breasts. Although several techniques such as mammography, xeromammography, ultrasound, thermography, and computed tomographic (CT) scanning have been proven to be useful to detect implant rupture, they have several disadvantages and lack specificity. In the current study, we have established magnetic resonance imaging (MRI) as a definitive, reliable, and reproducible technique to diagnose both intracapsular and extracapsular ruptures. The study was conducted in 100 symptomatic patients. Our imaging parameters were able to identify ruptures in implants with silicone shells. All the ruptures showed the presence of wavy lines, free-floating silicone shell within the gel ("free-floating loose-thread sign" or "linguine sign"). We had a 3.75 percent incidence of false-positive and false-negative results. The sensitivity for detection of silicone implant rupture was 76 percent, with a specificity of 97 percent. In addition, we also were able to identify the artifacts that may interfere with the definitive diagnosis of implant rupture.
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Mixture models for detecting differentially expressed genes in microarrays.
Jones, Liat Ben-Tovim; Bean, Richard; McLachlan, Geoffrey J; Zhu, Justin Xi
2006-10-01
An important and common problem in microarray experiments is the detection of genes that are differentially expressed in a given number of classes. As this problem concerns the selection of significant genes from a large pool of candidate genes, it needs to be carried out within the framework of multiple hypothesis testing. In this paper, we focus on the use of mixture models to handle the multiplicity issue. With this approach, a measure of the local FDR (false discovery rate) is provided for each gene. An attractive feature of the mixture model approach is that it provides a framework for the estimation of the prior probability that a gene is not differentially expressed, and this probability can subsequently be used in forming a decision rule. The rule can also be formed to take the false negative rate into account. We apply this approach to a well-known publicly available data set on breast cancer, and discuss our findings with reference to other approaches.
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Quantum Biometrics with Retinal Photon Counting
NASA Astrophysics Data System (ADS)
Loulakis, M.; Blatsios, G.; Vrettou, C. S.; Kominis, I. K.
2017-10-01
It is known that the eye's scotopic photodetectors, rhodopsin molecules, and their associated phototransduction mechanism leading to light perception, are efficient single-photon counters. We here use the photon-counting principles of human rod vision to propose a secure quantum biometric identification based on the quantum-statistical properties of retinal photon detection. The photon path along the human eye until its detection by rod cells is modeled as a filter having a specific transmission coefficient. Precisely determining its value from the photodetection statistics registered by the conscious observer is a quantum parameter estimation problem that leads to a quantum secure identification method. The probabilities for false-positive and false-negative identification of this biometric technique can readily approach 10-10 and 10-4, respectively. The security of the biometric method can be further quantified by the physics of quantum measurements. An impostor must be able to perform quantum thermometry and quantum magnetometry with energy resolution better than 10-9ℏ , in order to foil the device by noninvasively monitoring the biometric activity of a user.
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Brown, Charlotte A.; Bogers, Johnannes; Sahebali, Shaira; Depuydt, Christophe E.; De Prins, Frans; Malinowski, Douglas P.
2012-01-01
Since the Pap test was introduced in the 1940s, there has been an approximately 70% reduction in the incidence of squamous cell cervical cancers in many developed countries by the application of organized and opportunistic screening programs. The efficacy of the Pap test, however, is hampered by high interobserver variability and high false-negative and false-positive rates. The use of biomarkers has demonstrated the ability to overcome these issues, leading to improved positive predictive value of cervical screening results. In addition, the introduction of HPV primary screening programs will necessitate the use of a follow-up test with high specificity to triage the high number of HPV-positive tests. This paper will focus on protein biomarkers currently available for use in cervical cancer screening, which appear to improve the detection of women at greatest risk for developing cervical cancer, including Ki-67, p16INK4a, BD ProEx C, and Cytoactiv HPV L1. PMID:22481919
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Shaw, Colette M; Flanagan, Fidema L; Fenlon, Helen M; McNicholas, Michelle M
2009-02-01
To assesses consensus review of discordant screening mammography findings in terms of its sensitivity, safety, and effect on overall performance in the first 6 years of operation of the Irish National Breast Screening Program (NBSP). Women who participated in the Irish NBSP gave written informed consent for use of their data for auditing purposes. Local ethics committee approval was obtained. The study population consisted of women who participated in the Irish NBSP and underwent initial screening mammography at one of the two screening centers serving the eastern part of Ireland between 2000 and 2005. Independent double reading of mammograms was performed. When the readers disagreed regarding referral, the case was reviewed by a consensus panel. Of the 128 569 screenings performed, 1335 (1%) were discussed by consensus. Of the 1335 cases discussed by consensus, 606 (45.39%) were recalled for further assessment. This resulted in an overall recall rate of 4.41%. In those recalled to assessment, 71 cases of malignant disease were diagnosed (ductal carcinoma in situ, n = 24; invasive cancer, n = 47). The remaining 729 patients were returned to biennial screening. Of these 729 patients, seven had false-negative findings that were identified in the subsequent screening round. Use of the highest reader recall method, in which a patient is recalled if her findings are deemed abnormal by either reader, could potentially increase the cancer detection rate by 0.6 per 1000 women screened but would increase the recall rate by 12.69% and the number of false-positive findings by 15.37%. The consensus panel identified 71 (7.33%) of 968 cancers diagnosed. Consensus review substantially reduced the number of cases recalled and was associated with a low false-negative rate.
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Bennie, George; Vorster, Mariza; Buscombe, John; Sathekge, Mike
2015-01-01
Single-photon emission computed tomography-computed tomography (SPECT-CT) allows for physiological and anatomical co-registration in sentinel lymph node (SLN) mapping and offers additional benefits over conventional planar imaging. However, the clinical relevance when considering added costs and radiation burden of these reported benefits remains somewhat uncertain. This study aimed to evaluate the possible added value of SPECT-CT and intra-operative gamma-probe use over planar imaging alone in the South African setting. 80 patients with breast cancer or malignant melanoma underwent both planar and SPECT-CT imaging for SLN mapping. We assessed and compared the number of nodes detected on each study, false positive and negative findings, changes in surgical approach and or patient management. In all cases where a sentinel node was identified, SPECT-CT was more accurate anatomically. There was a significant change in surgical approach in 30 cases - breast cancer (n = 13; P 0.001) and malignant melanoma (n = 17; P 0.0002). In 4 cases a node not identified on planar imaging was seen on SPECT-CT. In 16 cases additional echelon nodes were identified. False positives were excluded by SPECT-CT in 12 cases. The addition of SPECT-CT and use of intra-operative gamma-probe to planar imaging offers important benefits in patients who present with breast cancer and melanoma. These benefits include increased nodal detection, elimination of false positives and negatives and improved anatomical localization that ultimately aids and expedites surgical management. This has been demonstrated in the context of industrialized country previously and has now also been confirmed in the setting of a emerging-market nation.
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Sorensen, James P R; Baker, Andy; Cumberland, Susan A; Lapworth, Dan J; MacDonald, Alan M; Pedley, Steve; Taylor, Richard G; Ward, Jade S T
2018-05-01
We assess the use of fluorescent dissolved organic matter at excitation-emission wavelengths of 280nm and 360nm, termed tryptophan-like fluorescence (TLF), as an indicator of faecally contaminated drinking water. A significant logistic regression model was developed using TLF as a predictor of thermotolerant coliforms (TTCs) using data from groundwater- and surface water-derived drinking water sources in India, Malawi, South Africa and Zambia. A TLF threshold of 1.3ppb dissolved tryptophan was selected to classify TTC contamination. Validation of the TLF threshold indicated a false-negative error rate of 15% and a false-positive error rate of 18%. The threshold was unsuccessful at classifying contaminated sources containing <10 TTC cfu per 100mL, which we consider the current limit of detection. If only sources above this limit were classified, the false-negative error rate was very low at 4%. TLF intensity was very strongly correlated with TTC concentration (ρ s =0.80). A higher threshold of 6.9ppb dissolved tryptophan is proposed to indicate heavily contaminated sources (≥100 TTC cfu per 100mL). Current commercially available fluorimeters are easy-to-use, suitable for use online and in remote environments, require neither reagents nor consumables, and crucially provide an instantaneous reading. TLF measurements are not appreciably impaired by common intereferents, such as pH, turbidity and temperature, within typical natural ranges. The technology is a viable option for the real-time screening of faecally contaminated drinking water globally. Copyright © 2017 Natural Environment Research Council (NERC), as represented by the British Geological Survey (BGS. Published by Elsevier B.V. All rights reserved.
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Local connected fractal dimension analysis in gill of fish experimentally exposed to toxicants.
Manera, Maurizio; Giari, Luisa; De Pasquale, Joseph A; Sayyaf Dezfuli, Bahram
2016-06-01
An operator-neutral method was implemented to objectively assess European seabass, Dicentrarchus labrax (Linnaeus, 1758) gill pathology after experimental exposure to cadmium (Cd) and terbuthylazine (TBA) for 24 and 48h. An algorithm-derived local connected fractal dimension (LCFD) frequency measure was used in this comparative analysis. Canonical variates (CVA) and linear discriminant analysis (LDA) were used to evaluate the discrimination power of the method among exposure classes (unexposed, Cd exposed, TBA exposed). Misclassification, sensitivity and specificity, both with original and cross-validated cases, were determined. LCFDs frequencies enhanced the differences among classes which were visually selected after their means, respective variances and the differences between Cd and TBA exposed means, with respect to unexposed mean, were analyzed by scatter plots. Selected frequencies were then scanned by means of LDA, stepwise analysis, and Mahalanobis distance to detect the most discriminative frequencies out of ten originally selected. Discrimination resulted in 91.7% of cross-validated cases correctly classified (22 out of 24 total cases), with sensitivity and specificity, respectively, of 95.5% (1 false negative with respect to 21 really positive cases) and 75% (1 false positive with respect to 3 really negative cases). CVA with convex hull polygons ensured prompt, visually intuitive discrimination among exposure classes and graphically supported the false positive case. The combined use of semithin sections, which enhanced the visual evaluation of the overall lamellar structure; of LCFD analysis, which objectively detected local variation in complexity, without the possible bias connected to human personnel; and of CVA/LDA, could be an objective, sensitive and specific approach to study fish gill lamellar pathology. Furthermore this approach enabled discrimination with sufficient confidence between exposure classes or pathological states and avoided misdiagnosis. Copyright © 2016 Elsevier B.V. All rights reserved.
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Gabriel, M; Muehllechner, P; Decristoforo, C; von Guggenberg, E; Kendler, D; Prommegger, R; Profanter, C; Moncayo, R; Virgolini, I
2005-09-01
To evaluate the use of 99mTc-EDDA-hydrazinonicotinyl-Tyr3-octreotide (Tc-TOC) for staging and follow-up of neuroendocrine gastro-entero-pancreatic (GEP) tumors with special focus on the acquisition protocol including single photon emission computed tomography (SPECT). Eighty-eight patients (37 female, 51 male; age range: 16 to 81 years; mean age: 56.3 years) were studied: 42 patients for staging after initial histological confirmation and 46 patients during post-therapy follow-up. An average activity of 400 MBq of the radiopharmaceutical was injected. All tumors originated from neuroendocrine tissue of the gastroenteropancreatic tract. Whole body scintigrams at 4 h postinjection and SPECT of the abdomen were obtained in all patients. Additional planar images of the abdomen were acquired at 2 h after injection in 68 patients. The Tc-TOC scan result was true-positive in 56 patients, true-negative in 17, false-negative in 14, and false-positive in 1 patient. The false-positive finding was caused by a colonic adenoma. Overall, a scan sensitivity of 80% (56/70 patients), specificity of 94.4% (17/18 patients) and accuracy of 82.9% (73/88 patients) were calculated on patient basis. In total, Tc-TOC detected 357 foci in 69 patients. In 7 patients equivocal findings were observed in the bowel at 4 h postinjection without corresponding tracer uptake in the scan 2 h earlier, meaning that these abnormal findings were correctly classified as non-malignant. In addition to planar views, SPECT revealed further 62 lesions. Tc-TOC with one-day, dual-time acquisition protocol is an accurate staging procedure in patients with neuroendocrine GEP tumors. SPECT shows high sensitivity for detection of abdominal lesions, while earlier images improve the reliability of abnormal abdominal findings.
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A neighboring structure reconstructed matching algorithm based on LARK features
NASA Astrophysics Data System (ADS)
Xue, Taobei; Han, Jing; Zhang, Yi; Bai, Lianfa
2015-11-01
Aimed at the low contrast ratio and high noise of infrared images, and the randomness and ambient occlusion of its objects, this paper presents a neighboring structure reconstructed matching (NSRM) algorithm based on LARK features. The neighboring structure relationships of local window are considered based on a non-negative linear reconstruction method to build a neighboring structure relationship matrix. Then the LARK feature matrix and the NSRM matrix are processed separately to get two different similarity images. By fusing and analyzing the two similarity images, those infrared objects are detected and marked by the non-maximum suppression. The NSRM approach is extended to detect infrared objects with incompact structure. High performance is demonstrated on infrared body set, indicating a lower false detecting rate than conventional methods in complex natural scenes.
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Analysis of false results in a series of 835 fine needle aspirates of breast lesions.
Willis, S L; Ramzy, I
1995-01-01
To analyze cases of false diagnoses from a large series to help increase the accuracy of fine needle aspiration of palpable breast lesions. The results of FNA of 835 palpable breast lesions were analyzed to determine the reasons for false positive, false negative and false suspicious diagnoses. Of the 835 aspirates, 174 were reported as positive, 549 as negative and 66 as suspicious or atypical but not diagnostic of malignancy. Forty-six cases were considered unsatisfactory. Tissue was available for comparison in 286 cases. The cytologic diagnoses in these cases were reported as follows: positive, 125 (43.7%); suspicious, 33 (11.5%); atypical, 18 (6.2%); negative, 92 (32%); and unsatisfactory, 18 (6.2%). There was one false positive diagnosis, yielding a false positive rate of 0.8%. This lesion was a case of fibrocystic change with hyperplasia, focal fat necrosis and reparative atypia. There were 14 false negative cases, resulting in a false negative rate of 13.2%. Nearly all these cases were sampling errors and included infiltrating ductal carcinomas (9), ductal carcinomas in situ (2), infiltrating lobular carcinomas (2) and tubular carcinoma (1). Most of the suspicious and atypical lesions proved to be carcinomas (35/50). The remainder were fibroadenomas (6), fibrocystic change (4), gynecomastia (2), adenosis (2) and granulomatous mastitis (1). A positive diagnosis of malignancy by FNA is reliable in establishing the diagnosis and planning the treatment of breast cancer. The false-positive rate is very low, with only a single case reported in 835 aspirates. Most false negatives are due to sampling and not to interpretive difficulties. The category "suspicious but not diagnostic of malignancy" serves a useful purpose in management of patients with breast lumps.
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The abdominal technetium scan (a decade of experience)
DOE Office of Scientific and Technical Information (OSTI.GOV)
Cooney, D.R.; Duszynski, D.O.; Camboa, E.
1982-10-01
Out of 270 children with gastrointestinal symptoms, the indications for technetium scanning were: gastrointestinal tract bleeding (165 patients), abdominal pain (99 patients) and a history of intussusception (6 patients). Thirty children had abnormal findings, while the remaining 240 patients had normal scans. Four of the 30 children with positive scans were not explored, while the others underwent laparotomy. Of the 26 operated patients, 12 (46%) had a Meckel's diverticulum. Nine patients (34%) had other pathologic lesions that were detected by the scan. Five had true false positives as no pathologic lesions were found. Of the 240 children with negative scans,more » 19 were eventually explored because of persistent symptoms or clinical findings. Two of these had a Meckel's diverticulum. Eleven had a negative exploration while six had other surgical lesions. Technitium scan should reliably detect around 80%-90% of Meckel's diverticula. It will also accurately exclude the diagnosis of Meckel's diverticulum in over 90% of patients.« less