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Sample records for false positive reaction

  1. Biologically false positive reactions to serological tests for syphilis

    PubMed Central

    Kostant, George H.

    1956-01-01

    The frequency of biologically false positive reactions to serological tests for syphilis depends on a number of factors, including the individual immunological response, the number and type of serological tests performed, and the stage of the disease producing such reactions; the relative importance of such factors is discussed. The author also considers in detail the diseases or conditions giving rise to acute or chronic biologically false positive reactions. A variety of verification tests exists for differentiating the true syphilitic reaction from the biologically false positive reaction, but none is so accurate as the Treponema pallidum immobilization and immune adherence tests, which the author considers should be used when others have proved inconclusive. In the final section of his paper, he indicates the steps to be followed in attempting to distinguish between latent syphilis and biologically false positive reactions in persons with positive serological tests but no anamnestic or clinical evidence of syphilis. PMID:13329848

  2. Elimination of false-positive polymerase chain reaction results resulting from hole punch carryover contamination.

    PubMed

    Bonne, Nicolai; Clark, Phillip; Shearer, Patrick; Raidal, Shane

    2008-01-01

    The collection of biological material (e.g., blood) directly onto filter paper for subsequent use in laboratory assays such as polymerase chain reaction (PCR), has become a common practice. Dried cells or fluid on the paper can be readily rehydrated and retrieved into a standard volume of an appropriate elution buffer but introduces a dilution factor to the sample. The use of a common cutting instrument for excising a standard-sized piece of paper that contains the material also introduces the potential for transferring biological material from one sample to subsequent samples, causing false-positive results by PCR. In the present study, filter-paper-collected blood that contained beak and feather disease virus was used to determine if viral DNA could be transferred between samples by a hole punch used to excise sequential filter papers. It was determined that false-positive results could be obtained at least 13 times after a positive sample. Subsequently, the efficacy of 4 methods of hole punch disinfection, flaming, VirkonS, bleach, and a bleach-ethanol combination, was assessed. The only effective and practical method to destroy DNA was a method where the hole punch was agitated in commercial bleach, rinsed in water, the water was displaced with 100% ethanol and air-dried. This method was simple, cheap, and relatively rapid, and allowed for the use of a single hole punch for a series of samples, without carryover contamination and consequent false-positive results.

  3. Diagnostic performance of serological tests for swine brucellosis in the presence of false positive serological reactions.

    PubMed

    Dieste-Pérez, L; Blasco, J M; de Miguel, M J; Moriyón, I; Muñoz, P M

    2015-04-01

    Swine brucellosis caused by Brucella suis biovar 2 is an emerging disease in Europe. Currently used diagnostic tests for swine brucellosis detect antibodies to the O-polysaccharide (O-PS) of Brucella smooth lipopolysaccharide (S-LPS) but their specificity is compromised by false-positive serological reactions (FPSRs) when bacteria carrying cross-reacting O-PS infect pigs. FPSRs occur throughout Europe, and the only tool available for a specific B. suis diagnosis is the intradermal test with Brucella protein extracts free of O-PS or S-LPS. Using sera of 162 sows naturally infected by B. suis biovar 2, 406 brucellosis-free sows, and 218 pigs of brucellosis-free farms affected by FPSR, we assessed the diagnostic performance of an indirect ELISA with rough LPS (thus devoid of O-PS) and of gel immunodiffusion, counterimmunoelectrophoresis, latex agglutination and indirect ELISA with O-PS free proteins in comparison with several S-LPS tests (Rose Bengal, complement fixation, gel immunodiffusion and indirect ELISA). When adjusted to 100% specificity, the sensitivity of the rough LPS ELISA was very low (30%), and adoption of other cut-offs resulted in poor specificity/sensitivity ratios. Although their specificity was 100%, the sensitivity of protein tests (ELISA, latex agglutination, counterimmunoelectrophoresis, and gel immunodiffusion) was only moderate (45, 58, 61 and 63%, respectively). Among S-LPS tests, gel immunodiffusion was the only test showing acceptable sensitivity/specificity (68 and 100%, respectively). Despite these shortcomings, and when the purpose is to screen out FPSR at herd level, gel immunodiffusion tests may offer a technically simple and practical alternative to intradermal testing.

  4. Regulatory false positives: true, false, or uncertain?

    PubMed

    Cox, Louis Anthony

    2007-10-01

    Hansen et al. (2007) recently assessed the historical performance of the precautionary principle in 88 specific cases, concluding that "applying our definition of a regulatory false positive, we were able to identify only four cases that fit the definition of a false positive." Empirically evaluating how prone the precautionary principle is to classify nonproblems as problems ("false positives") is an excellent idea. Yet, Hansen et al.'s implementation of this idea applies a diverse set of questionable criteria to label many highly uncertain risks as "real" even when no real or potential harm has actually been demonstrated. Examples include treating each of the following as reasons to categorize risks as "real": considering that a company's actions contaminated its own product; lack of a known exposure threshold for health effects; occurrence of a threat; treating deliberately conservative (upper-bound) regulatory assumptions as if they were true values; treating assumed exposures of children to contaminated soils (by ingestion) as evidence that feared dioxin risks are real; and treating claimed (sometimes ambiguous) epidemiological associations as if they were known to be true causal relations. Such criteria can classify even nonexistent and unknown risks as "real," providing an alternative possible explanation for why the authors failed to find more false positives, even if they exist.

  5. False Position, Double False Position and Cramer's Rule

    ERIC Educational Resources Information Center

    Boman, Eugene

    2009-01-01

    We state and prove the methods of False Position (Regula Falsa) and Double False Position (Regula Duorum Falsorum). The history of both is traced from ancient Egypt and China through the work of Fibonacci, ending with a connection between Double False Position and Cramer's Rule.

  6. The Kepler False Positive Table

    NASA Astrophysics Data System (ADS)

    Bryson, Steve; Kepler False Positive Working Group

    2015-01-01

    The Kepler Space Telescope has detected thousands of candidate exoplanets by observing transit signals in a sample of more than 190,000 stars. Many of these transit signals are false positives, defined as a transit-like signal that is not due to a planet orbiting the target star (or a bound companion if the target is a multiple-star system). Astrophysical causes of false positives include background eclipsing binaries, planetary transits not associated with the target star, and non-planetary eclipses of the target star by stellar companions. The fraction of Kepler planet candidates that are false positives ranges from about 10% at high Galactic latitudes to 40% at low Galactic latitudes. Creating a high-reliability planet candidate catalog for statistical studies such as occurrence rate calculations requires removing clearly identified false positives.The Kepler Object of Interest (KOI) catalog at the NExScI NASA Exoplanet Archive flags false positives, and will soon provide a high-level classification of false positives, but lacks detailed description of why a KOI was determined to be a false positive. The Kepler False Positive Working Group (FPWG) examines each false positive in detail to certify that it is correctly identified as a false positive, and determines the primary reason(s) a KOI is classified as a false positive. The work of the FPWG will be published as the Kepler False Positive Table, hosted at the NExScI NASA Exoplanet Archive.The Kepler False Positive Table provides detailed information on the evidence for background binaries, transits caused by stellar companions, and false alarms. In addition to providing insight into the Kepler false positive population, the false positive table gives information about the background binary population and other areas of astrophysical interest. Because a planet around a star not associated with the target star is considered a false positive, the false positive table likely contains further planet candidates

  7. General false positive ELISA reactions in visceral leishmaniasis. Implications for the use of enzyme immunoassay analyses in tropical Africa.

    PubMed

    Elshafie, Amir I; Mullazehi, Mohammed; Rönnelid, Johan

    2016-04-01

    Leishmaniasis is a neglected disease in tropical countries. Clinical and laboratory features may mimic autoimmune diseases and this can complicate the Leishmania diagnosis. Due to our previous investigation for false anti-CCP2 reactivity in Leishmania-infected subjects and our interest in immunity against the joint-specific collagen type II (CII) in rheumatoid arthritis (RA) we investigated the same cohort for anti-CII antibodies. We found elevated anti-CII reactivity in Leishmania-infected patients as compared to controls. When anti-CII OD values were compared with BSA-blocked control plates we found higher reactivity against BSA than in CII-coated plates in many Leishmania-infected patients. The percentage of such false positive anti-CII reactions increased with inflammatory activity, and was found in almost all Leishmania patients with highly active inflammatory disease, but was as low in Sudanese healthy controls as well as among Swedish RA patients. The correlation coefficients between false positive anti-CII and anti-CCP2 measured with a commercial ELISA were highest for patients with the most inflammatory disease but non-significant for Sudanese controls and Swedish RA patients, arguing that our findings may have general implications for ELISA measurements in leishmaniasis. ELISA investigations in areas endemic for leishmaniasis might benefit from individual-specific control wells for each serum sample. This approach might also be applicable to other geographical areas or patient groups with high incidence of inflammatory and infectious diseases.

  8. False positives in imaging genetics.

    PubMed

    Meyer-Lindenberg, Andreas; Nicodemus, Kristin K; Egan, Michael F; Callicott, Joseph H; Mattay, Venkata; Weinberger, Daniel R

    2008-04-01

    Imaging genetics provides an enormous amount of functional-structural data on gene effects in living brain, but the sheer quantity of potential phenotypes raises concerns about false discovery. Here, we provide the first empirical results on false positive rates in imaging genetics. We analyzed 720 frequent coding SNPs without significant association with schizophrenia and a subset of 492 of these without association with cognitive function. Effects on brain structure (using voxel-based morphometry, VBM) and brain function, using two archival imaging tasks, the n-back working memory task and an emotional face matching task, were studied in whole brain and regions of interest and corrected for multiple comparisons using standard neuroimaging procedures. Since these variants are unlikely to impact relevant brain function, positives obtained provide an upper empirical estimate of the false positive association rate. In a separate analysis, we randomly permuted genotype labels across subjects, removing any true genotype-phenotype association in the data, to derive a lower empirical estimate. At a set correction level of 0.05, in each region of interest and data set used, the rate of positive findings was well below 5% (0.2-4.1%). There was no relationship between the region of interest and the false positive rate. Permutation results were in the same range as empirically derived rates. The observed low rates of positives provide empirical evidence that the type I error rate is well controlled by current commonly used correction procedures in imaging genetics, at least in the context of the imaging paradigms we have used. In fact, our observations indicate that these statistical thresholds are conservative.

  9. Specificity dependence between serological tests for diagnosing bovine brucellosis in Brucella-free farms showing false positive serological reactions due to Yersinia enterocolitica O:9

    PubMed Central

    2005-01-01

    Abstract When brucellosis false positive serological reactions happen in cattle, the serial use of pairs of specificity-correlated serological tests (rose bengal, complement fixation, competitive ELISA) results in specificities lower than expected. In this situation, highly specific tests, such as the indirect ELISA used alone, may be more adequate than serial testing. PMID:16454384

  10. The Dutch Brucella abortus monitoring programme for cattle: the impact of false-positive serological reactions and comparison of serological tests.

    PubMed

    Emmerzaal, A; de Wit, J J; Dijkstra, Th; Bakker, D; van Zijderveld, F G

    2002-02-01

    The Dutch national Brucella abortus eradication programme for cattle started in 1959. Sporadic cases occurred yearly until 1995; the last infected herd was culled in 1996. In August 1999 the Netherlands was declared officially free of bovine brucellosis by the European Union. Before 1999, the programme to monitor the official Brucella-free status of bovine herds was primarily based on periodical testing of dairy herds with the milk ring test (MRT) and serological testing of all animals older than 1 year of age from non-dairy herds, using the micro-agglutination test (MAT) as screening test. In addition, serum samples of cattle that aborted were tested with the MAT. The high number of false positive reactions in both tests and the serum agglutination test (SAT) and complement fixation test (CFT) used for confirmation seemed to result in unnecessary blockade of herds, subsequent testing and slaughter of animals. For this reason, a validation study was performed in which three indirect enzyme-linked immunosorbent assays (ELISAs), the CFT and the SAT were compared using a panel of sera from brucellosis-free cattle, sera from experimentally infected cattle, and sera from cattle experimentally infected with bacteria which are known to induce cross-reactive antibodies (Pasteurella, Salmonella, Yersinia, and Escherichia). Moreover, four ELISAs and the MRT were compared using a panel of 1000 bulk milk samples from Brucella-free herds and 12 milk samples from Brucella abortus- infected cattle. It is concluded that the ELISA obtained from ID-Lelystad is the most suitable test to monitor the brucelosis free status of herds because it gives rise to fewer false-positive reactions than the SAT.

  11. Possibility of false-positive detection for sporozoites in mosquitos (Diptera: Culicidae) by nested polymerase chain reaction using Plasmodium yoelii genomic DNA.

    PubMed

    Tsuzuki, A; Toma, T; Miyagi, I; Toma, H; Arakawa, T; Sato, Y; Kobayashi, J; Mugissa, M F

    2001-06-01

    Anopheles stephensi Liston and An. saperoi Bohart and Ingram infected with the rodent malaria parasite Plasmodium yoelii nigeriense. They were examined 12 and 19 days after blood feeding for sporozoites in head with anterior thorax (HT) and oocysts in abdomen with posterior thorax (AB) by light microscopy and by the nested polymerase chain reaction (nested PCR-based on the amplification of the sequences of the small subunit ribosomal RNA gene). The detection rate of parasite DNA by nested PCR in HT samples 12 days after blood feeding was similar to that by microscopic method. However, in HT samples 19 days after blood feeding, the rate by the PCR method was higher than that by the microscopic method. The incidence of sporozoites in salivary glands of infected mosquitos for 12 days after blood sucking was examined by the PCR method. Parasite DNA in HT of Aedes albopictus Skuse (a non vector for the rodent malaria) as well as An. stephensi and An. saperoi was detected for up to 4 days after feeding on mouse with the rodent malaria parasites. The results indicate that when the PCR method is used for detection of sporozoites of human malaria in mosquitos collected in the field, there are possibilities of including false-positive data for mosquitos that have just or recently fed on human blood infected with malaria (erythrocytic form).

  12. False positive reduction for lung nodule CAD

    NASA Astrophysics Data System (ADS)

    Zhao, Luyin; Boroczky, Lilla; Drysdale, Jeremy; Agnihotri, Lalitha; Lee, Michael C.

    2007-03-01

    Computer-aided detection (CAD) algorithms 'automatically' identify lung nodules on thoracic multi-slice CT scans (MSCT) thereby providing physicians with a computer-generated 'second opinion'. While CAD systems can achieve high sensitivity, their limited specificity has hindered clinical acceptance. To overcome this problem, we propose a false positive reduction (FPR) system based on image processing and machine learning to reduce the number of false positive lung nodules identified by CAD algorithms and thereby improve system specificity. To discriminate between true and false nodules, twenty-three 3D features were calculated from each candidate nodule's volume of interest (VOI). A genetic algorithm (GA) and support vector machine (SVM) were then used to select an optimal subset of features from this pool of candidate features. Using this feature subset, we trained an SVM classifier to eliminate as many false positives as possible while retaining all the true nodules. To overcome the imbalanced nature of typical datasets (significantly more false positives than true positives), an intelligent data selection algorithm was designed and integrated into the machine learning framework, thus further improving the FPR rate. Three independent datasets were used to train and validate the system. Using two datasets for training and the third for validation, we achieved a 59.4% FPR rate while removing one true nodule on the validation datasets. In a second experiment, 75% of the cases were randomly selected from each of the three datasets and the remaining cases were used for validation. A similar FPR rate and true positive retention rate was achieved. Additional experiments showed that the GA feature selection process integrated with the proposed data selection algorithm outperforms the one without it by 5%-10% FPR rate. The methods proposed can be also applied to other application areas, such as computer-aided diagnosis of lung nodules.

  13. Detection of Yersinia enterocolitica serotype O:9 in the faeces of cattle with false positive reactions in serological tests for brucellosis in Ireland.

    PubMed

    O'Grady, Don; Kenny, Kevin; Power, Seamus; Egan, John; Ryan, Fergus

    2016-10-01

    Intestinal infection by Yersinia enterocolitica serotype O:9 (YeO9) in cattle has been linked to false positive serological reactivity (FPSR) in diagnostic tests for brucellosis. Although eradicated in Ireland, brucellosis monitoring still identifies seropositive animals, usually one or two (termed singletons) per herd, which are classed as FPSR. To investigate a link between FPSR and YeO9, faeces and blood were collected from singleton FPSR cattle, and from companion animals, in eight selected herds with more than one FPSR animal, for YeO9 culture and Brucella serology. YeO9 was isolated from 76/474 (16%) FPSR singletons in 309 herds, but not from any of 621 animals in 122 control non-FPSR herds. In the FPSR herds 52/187 (27.8%) animals were culture positive, and 17% of the isolates were from seronegative animals. Seropositive animals were more likely to have a rising antibody titre when culture positive.

  14. Detection of Yersinia enterocolitica serotype O:9 in the faeces of cattle with false positive reactions in serological tests for brucellosis in Ireland.

    PubMed

    O'Grady, Don; Kenny, Kevin; Power, Seamus; Egan, John; Ryan, Fergus

    2016-10-01

    Intestinal infection by Yersinia enterocolitica serotype O:9 (YeO9) in cattle has been linked to false positive serological reactivity (FPSR) in diagnostic tests for brucellosis. Although eradicated in Ireland, brucellosis monitoring still identifies seropositive animals, usually one or two (termed singletons) per herd, which are classed as FPSR. To investigate a link between FPSR and YeO9, faeces and blood were collected from singleton FPSR cattle, and from companion animals, in eight selected herds with more than one FPSR animal, for YeO9 culture and Brucella serology. YeO9 was isolated from 76/474 (16%) FPSR singletons in 309 herds, but not from any of 621 animals in 122 control non-FPSR herds. In the FPSR herds 52/187 (27.8%) animals were culture positive, and 17% of the isolates were from seronegative animals. Seropositive animals were more likely to have a rising antibody titre when culture positive. PMID:27687940

  15. Constraining Oxygen False Positives in Planetary Atmospheres

    NASA Astrophysics Data System (ADS)

    Harman, C. E.; Schottelkotte, J. C.; Kasting, J. F.

    2014-03-01

    Oxygen (O2) and ozone (O3) in the present Earth's atmosphere are byproducts of oxygenic photosynthesis coupled with organic carbon burial. On Earth, no known abiotic surface process would be able to generate such an atmosphere, and by extension, lifeless exoplanets are expected to be devoid of O2. As a result, molecular oxygen and ozone are often seen as convincing signposts for life. Recently, however, a number of authors have demonstrated the abiotic generation of molecular oxygen in a planetary atmosphere, either under oxidizing conditions (Hu et al., 2013) or around an M star (Tian et al., 2013). This èfalse positive', if verified, would remove oxygen and ozone from an already short list of easily detectable biosignatures. We explore oxygen false positives with our 1-D photochemical model, updated from Segura et al. (2007). Preliminary results show that if water vapor photolysis longward of ~200 nm is neglected, substantial amounts of CO and O2 can build up in the lower part of the atmosphere. Additionally, the ultimate fate of CO and O2 produced in such atmospheres is strongly dependent on the imposed lower boundary condition, with low depositional velocities corresponding to higher mixing ratios in the lower atmosphere. The deposition velocity of a gas depends on it dissolved concentration, however, and so one needs to consider the chemistry of these gases in solution. Ongoing work seeks to test the conclusions of Tian et al., (2013) by exploring this dependence on ocean chemistry and by including spectra from AD Leo (an active M-dwarf, used by Domagal-Goldman et al., (2011)) to compare with the M-dwarf spectra used by Tian et al.

  16. Accounting for False Positive HIV Tests: Is Visceral Leishmaniasis Responsible?

    PubMed Central

    Shanks, Leslie; Ritmeijer, Koert; Piriou, Erwan; Siddiqui, M. Ruby; Kliescikova, Jarmila; Pearce, Neil; Ariti, Cono; Muluneh, Libsework; Masiga, Johnson; Abebe, Almaz

    2015-01-01

    Background Co-infection with HIV and visceral leishmaniasis is an important consideration in treatment of either disease in endemic areas. Diagnosis of HIV in resource-limited settings relies on rapid diagnostic tests used together in an algorithm. A limitation of the HIV diagnostic algorithm is that it is vulnerable to falsely positive reactions due to cross reactivity. It has been postulated that visceral leishmaniasis (VL) infection can increase this risk of false positive HIV results. This cross sectional study compared the risk of false positive HIV results in VL patients with non-VL individuals. Methodology/Principal Findings Participants were recruited from 2 sites in Ethiopia. The Ethiopian algorithm of a tiebreaker using 3 rapid diagnostic tests (RDTs) was used to test for HIV. The gold standard test was the Western Blot, with indeterminate results resolved by PCR testing. Every RDT screen positive individual was included for testing with the gold standard along with 10% of all negatives. The final analysis included 89 VL and 405 non-VL patients. HIV prevalence was found to be 12.8% (47/ 367) in the VL group compared to 7.9% (200/2526) in the non-VL group. The RDT algorithm in the VL group yielded 47 positives, 4 false positives, and 38 negatives. The same algorithm for those without VL had 200 positives, 14 false positives, and 191 negatives. Specificity and positive predictive value for the group with VL was less than the non-VL group; however, the difference was not found to be significant (p = 0.52 and p = 0.76, respectively). Conclusion The test algorithm yielded a high number of HIV false positive results. However, we were unable to demonstrate a significant difference between groups with and without VL disease. This suggests that the presence of endemic visceral leishmaniasis alone cannot account for the high number of false positive HIV results in our study. PMID:26161864

  17. Frequency of false-negative reactions to the fragrance mix.

    PubMed

    de Groot, A C; van der Kley, A M; Bruynzeel, D P; Meinardi, M M; Smeenk, G; van Joost, T; Pavel, S

    1993-03-01

    To estimate the frequency of false-negative reactions to the fragrance mix, the 8 constituents of the mix in concentrations of 5% (2% for cinnamic aldehyde) were added to the European standard series for routine testing. Patients with positive reactions to individual ingredients in the absence of a reaction to the mix were retested with serial dilutions. In a 4-month period, 677 patients were tested. 61 (9%) reacted to the mix and to 1 or more of the ingredients. 4 patients (0.6% of all patients tested and 6.2% of the patients allergic to fragrances) had false-negative reactions to the mix. They were allergic to cinnamic alcohol, geraniol, isoeugenol and oak moss (1 reaction each), in the absence of a reaction to the fragrance mix. It is concluded that the currently used concentration of the mix (8 x 1%) not infrequently results in false-negative reactions, and that further research should be done to overcome this problem.

  18. 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…

  19. Generalized site occupancy models allowing for false positive and false negative errors

    USGS Publications Warehouse

    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.

  20. False-Positive Stress Echocardiograms: A Continuing Challenge

    PubMed Central

    Qamruddin, Salima

    2016-01-01

    Background: Stress echocardiography is an integral test in the cardiac diagnostic laboratory and has high sensitivity and specificity. Despite the excellent specificity of stress echocardiography, we continue to see a subset of patients with false-positive tests (defined as <50% diameter stenosis on subsequent coronary angiography). These false-positive findings present a management challenge because it remains unclear if and how to treat these patients. Methods: This article reviews relevant clinical studies and their outcomes. Results: Studies suggest that a group of patients develops a hypertensive response to exercise and therefore may have false-positive stress echocardiography. Hence, superior blood pressure control prior to stress echocardiography may prevent some false-positive tests. In addition, a subset of patients has microvascular abnormalities, vasomotor changes, endothelial dysfunction, and/or small vessel coronary disease that can lead to false-positive stress echocardiography. Conclusion: The evidence is insufficient to state that a false-positive stress echocardiography in the absence of obstructive coronary artery disease portends a poor outcome, but considerable evidence shows that some of these patients have microvascular abnormalities and endothelial dysfunction and consequently may benefit from aggressive medical management and further testing. PMID:27660577

  1. False-Positive Stress Echocardiograms: A Continuing Challenge

    PubMed Central

    Qamruddin, Salima

    2016-01-01

    Background: Stress echocardiography is an integral test in the cardiac diagnostic laboratory and has high sensitivity and specificity. Despite the excellent specificity of stress echocardiography, we continue to see a subset of patients with false-positive tests (defined as <50% diameter stenosis on subsequent coronary angiography). These false-positive findings present a management challenge because it remains unclear if and how to treat these patients. Methods: This article reviews relevant clinical studies and their outcomes. Results: Studies suggest that a group of patients develops a hypertensive response to exercise and therefore may have false-positive stress echocardiography. Hence, superior blood pressure control prior to stress echocardiography may prevent some false-positive tests. In addition, a subset of patients has microvascular abnormalities, vasomotor changes, endothelial dysfunction, and/or small vessel coronary disease that can lead to false-positive stress echocardiography. Conclusion: The evidence is insufficient to state that a false-positive stress echocardiography in the absence of obstructive coronary artery disease portends a poor outcome, but considerable evidence shows that some of these patients have microvascular abnormalities and endothelial dysfunction and consequently may benefit from aggressive medical management and further testing.

  2. Skin sensitization, false positives and false negatives: experience with guinea pig assays.

    PubMed

    Basketter, David A; Kimber, Ian

    2010-07-01

    The advent of the local lymph node assay (LLNA), and efforts to develop in vitro alternatives for the identification of skin sensitizing chemicals has focused attention on the issue of false positive and false negative results. In essence, the question becomes 'what is the gold standard?' In this context, attention has focused primarily on the LLNA as this is now the preferred assay for skin sensitization testing. However, for many years prior to introduction of the LLNA, the guinea pig maximization test and the occluded patch test of Buehler were the methods of choice. In order to encourage a more informed dialogue about the relative performance, accuracy and applicability of the LLNA and guinea pig tests, we have here considered the extent to which guinea pig methods were themselves subject to false positives and negative results. We describe and discuss here well-characterized examples of instances where both false negatives (including abietic acid and eugenol) or false positives (including vanillin and sulfanilic acid) have been recorded in guinea pig tests. These and other examples are discussed with particular reference to the fabrication of a gold standard dataset that is required for the validation of in vitro alternatives.

  3. Filtering False Positives Based on Server-Side Behaviors

    NASA Astrophysics Data System (ADS)

    Shimamura, Makoto; Hanaoka, Miyuki; Kono, Kenji

    Reducing the rate of false positives is of vital importance in enhancing the usefulness of signature-based network intrusion detection systems (NIDSs). To reduce the number of false positives, a network administrator must thoroughly investigate a lengthy list of signatures and carefully disable the ones that detect attacks that are not harmful to the administrator's environment. This is a daunting task; if some signatures are disabled by mistake, the NIDS fails to detect critical remote attacks. We designed a NIDS, TrueAlarm, to reduce the rate of false positives. Conventional NIDSs alert administrators that a malicious message has been detected, regardless of whether the message actually attempts to compromise the protected server. In contrast, TrueAlarm delays the alert until it has confirmed that an attempt has been made. The TrueAlarm NIDS cooperates with a server-side monitor that observes the protected server's behavior. TrueAlarm only alerts administrators when a server-side monitor has detected deviant server behavior that must have been caused by a message detected by a NIDS. Our experimental results revealed that TrueAlarm reduces the rate of false positives. Using actual network traffic collected over 14 days, TrueAlarm produced 46 false positives, while Snort, a conventional NIDS, produced 818.

  4. Screening for possible human carcinogens and mutagens. False positives, false negatives: statistical implications.

    PubMed

    Lovell, D P

    1989-07-01

    A screening method aimed at identifying potential human carcinogens using either animal cancer bioassays or short-term genotoxic assays has 4 possible results: true positive, true negative, false positive and false negative. Such a categorisation is superficially similar to the results of hypothesis testing in a statistical analysis. In this latter case the false positive rate is determined by the significance level of the test and the false negative rate by the statistical power of the test. Although the two types of categorisation appear somewhat similar, different statistical issues are involved in their interpretation. Statistical methods appropriate for the analysis of the results of a series of assays include the use of Bayes' theorem and multivariate methods such as clustering techniques for the selection of batteries of short-term test capable of a better prediction of potential carcinogens. The conclusions drawn from such studies are dependent upon the estimates of values of sensitivity and specificity used, the choice of statistical method and the nature of the data set. The statistical issues resulting from the analysis of specific genotoxicity experiments involve the choice of suitable experimental designs and appropriate analyses together with the relationship of statistical significance to biological importance. The purpose of statistical analysis should increasingly be to estimate and explore effects rather than for formal hypothesis testing.

  5. Balancing false positives and false negatives for the detection of differential expression in malignancies

    PubMed Central

    De Smet, F; Moreau, Y; Engelen, K; Timmerman, D; Vergote, I; De Moor, B

    2004-01-01

    A basic problem of microarray data analysis is to identify genes whose expression is affected by the distinction between malignancies with different properties. These genes are said to be differentially expressed. Differential expression can be detected by selecting the genes with P-values (derived using an appropriate hypothesis test) below a certain rejection level. This selection, however, is not possible without accepting some false positives and negatives since the two sets of P-values, associated with the genes whose expression is and is not affected by the distinction between the different malignancies, overlap. We describe a procedure for the study of differential expression in microarray data based on receiver-operating characteristic curves. This approach can be useful to select a rejection level that balances the number of false positives and negatives and to assess the degree of overlap between the two sets of P-values. Since this degree of overlap characterises the balance that can be reached between the number of false positives and negatives, this quantity can be seen as a quality measure of microarray data with respect to the detection of differential expression. As an example, we apply our method to data sets studying acute leukaemia. PMID:15354216

  6. Looking for Childhood Schizophrenia: Case Series of False Positives.

    ERIC Educational Resources Information Center

    Stayer, Catherine; Sporn, Alexandra; Gogtay, Nitin; Tossell, Julia; Lenane, Marge; Gochman, Peter; Rapoport, Judith L.

    2004-01-01

    Extensive experience with the diagnosis of childhood-onset schizophrenia indicates a high rate of false positives. Most mislabeled patients have chronic disabling, affective, or behavioral disorders. The authors report the cases of three children who passed stringent initial childhood-onset schizophrenia "screens" but had no chronic psychotic…

  7. Detecting False Positives in Multielement Designs: Implications for Brief Assessments

    ERIC Educational Resources Information Center

    Bartlett, Sara M.; Rapp, John T.; Henrickson, Marissa L.

    2011-01-01

    The authors assessed the extent to which multielement designs produced false positives using continuous duration recording (CDR) and interval recording with 10-s and 1-min interval sizes. Specifically, they created 6,000 graphs with multielement designs that varied in the number of data paths, and the number of data points per data path, using a…

  8. A Demonstration of Regression False Positive Selection in Data Mining

    ERIC Educational Resources Information Center

    Pinder, Jonathan P.

    2014-01-01

    Business analytics courses, such as marketing research, data mining, forecasting, and advanced financial modeling, have substantial predictive modeling components. The predictive modeling in these courses requires students to estimate and test many linear regressions. As a result, false positive variable selection ("type I errors") is…

  9. False Positive Probabilities for all Kepler Objects of Interest: 1284 Newly Validated Planets and 428 Likely False Positives

    NASA Astrophysics Data System (ADS)

    Morton, Timothy D.; Bryson, Stephen T.; Coughlin, Jeffrey L.; Rowe, Jason F.; Ravichandran, Ganesh; Petigura, Erik A.; Haas, Michael R.; Batalha, Natalie M.

    2016-05-01

    We present astrophysical false positive probability calculations for every Kepler Object of Interest (KOI)—the first large-scale demonstration of a fully automated transiting planet validation procedure. Out of 7056 KOIs, we determine that 1935 have probabilities <1% of being astrophysical false positives, and thus may be considered validated planets. Of these, 1284 have not yet been validated or confirmed by other methods. In addition, we identify 428 KOIs that are likely to be false positives, but have not yet been identified as such, though some of these may be a result of unidentified transit timing variations. A side product of these calculations is full stellar property posterior samplings for every host star, modeled as single, binary, and triple systems. These calculations use vespa, a publicly available Python package that is able to be easily applied to any transiting exoplanet candidate.

  10. 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.

  11. How the Sausage is Made: Kepler's False Alarms, False Positives, and Planet Candidates

    NASA Astrophysics Data System (ADS)

    Coughlin, J.

    2014-04-01

    The Kepler mission has now designated over 7,000 Kepler objects of interest (KOIs), or transit-like signatures, utilizing up to four years of data. The number of potentially habitable planet candidates (PCs) among this sample has risen significantly over time. However, starting with Kepler threshold crossing events (TCEs), there are initially about as many false alarms (FAs) detected as there are KOIs. Furthermore, due to its design, contamination from eclipsing binaries, variable stars, and other transiting planets result in a significant number of KOIs being designated as false positives (FPs). Many of these FAs and FPs occur at long orbital periods, where habitable planets are typically found. I will review the process of how an initial TCE becomes a KOI, and then is ultimately classified as a FA, FP, or PC, along with the various vetting tools employed. The understanding of this process is crucial to performing accurate statistical analyses on populations of habitable planet candidates discovered by Kepler.

  12. ``False Positive,'' an Apt Term and Concept for Volcanologists

    NASA Astrophysics Data System (ADS)

    Wunderman, R.

    2010-12-01

    A less-than-bold prediction is that signals that could presage an eruption, but later turn out not to have been predictive (false positives), will continue to vex volcanologists and societies touched by volcanic processes. At present, even at the most carefully monitored volcanoes, many remote-sensing, geophysical, and geochemical clues are often incompletely diagnostic. Even assessing multiple kinds of data cannot ensure successful prediction of eruption or eruptive behavior. Although we’ve witnessed improvements in instrumentation, a growing number of instructive examples, and advances in understanding, the concept of false positives might elevate public understanding since the term is in common use (eg., medical tests). The term helps reveal inherent uncertainty to the press and public, with much-needed emphasis on the limits of the data. Such understanding among the public is critical when scientists forecast an eruption that fails to materialize (“cry wolf”), a circumstance that can have profound negative consequences, including loss of credibility. Bayes’ theorem can calculate probabilities as well as the rates of false positives and false negatives. The rates are a function of both the accuracy of the test and the actual rate of occurrence of the phenomena in question. Globally, rates of occurrence differ for various volcanological processes. For example, dome extrusion is common, whereas caldera collapse, comparatively rare. The latter’s rarity may suggest caution in interpreting precursory signals that could indicate that outcome. Despite the risk of false positives, it may be appropriate to heed test results, even those of marginal reliability, because the consequences of disaster are much greater than the cost of avoidance. For example, risks of uncertain ash plumes detected by VAACs with remote sensing may be minimized by altering an aircraft’s route, a choice less onerous than confronting the danger of ash encounter.

  13. A textural approach for mass false positive reduction in mammography.

    PubMed

    Lladó, X; Oliver, A; Freixenet, J; Martí, R; Martí, J

    2009-09-01

    During the last decade several algorithms have been proposed for automatic mass detection in mammographic images. However, almost all these methods suffer from a high number of false positives. In this paper we propose a new approach for tackling this false positive reduction problem. The key point of our proposal is the use of Local Binary Patterns (LBP) for representing the textural properties of the masses. We extend the basic LBP histogram descriptor into a spatially enhanced histogram which encodes both the local region appearance and the spatial structure of the masses. Support Vector Machines (SVM) are then used for classifying the true masses from the ones being actually normal parenchyma. Our approach is evaluated using 1792 ROIs extracted from the DDSM database. The experiments show that LBP are effective and efficient descriptors for mammographic masses. Moreover, the comparison with current methods illustrates that our proposal obtains a better performance. PMID:19406614

  14. Consequences of treating false positive heparin-induced thrombocytopenia.

    PubMed

    Marler, Jacob; Unzaga, Jessica; Stelts, Sundae; Oliphant, Carrie S

    2015-11-01

    Identification of patients with heparin-induced thrombocytopenia is encumbered by false positive enzyme-linked immuno assay (ELISA) antibody results, therefore a serotonin release assay (SRA) is used for confirmation. Recently, several studies have demonstrated that increasing the optical density (OD) threshold (currently at 0.4) of the antibody test enhances the positive predictive value. The purpose of this study was to determine the frequency of patients who were ELISA antibody positive but SRA negative, and the costs and bleeding events associated with alternative anticoagulant treatment. We hypothesized that treating patients with a positive ELISA antibody OD value of <1.0 would result in increased cost and bleeding risk. This retrospective chart review was conducted on adult hospitalized patients from 2011 to 2013. Patients with positive ELISA antibodies (OD of 0.4-1.0) and an SRA result were included. Eighty-five patients were identified with positive antibodies (average OD of 0.66), 100 % of which were found to be SRA negative. A total of 59 patients (69 %) received alternative anticoagulants. The average duration of treatment was 3.1 days, and 4 patients (4.7 %) experienced a bleeding event. The cost of testing and laboratory monitoring was $36,346 and the cost of the alternative anticoagulants totaled $47,179. The total cost was $83,525, with an average total cost per patient of $982. This study adds to the body of literature suggesting treatment should only be initiated if the OD is one or greater. The high false positive rate caused increased cost and some bleeding events.

  15. Abort Trigger False Positive and False Negative Analysis Methodology for Threshold-Based Abort Detection

    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.

  16. A positive emotional bias in confabulatory false beliefs about place.

    PubMed

    Turnbull, Oliver H; Berry, Helen; Evans, Cathryn E Y

    2004-08-01

    Some neurological patients with medial frontal lesions exhibit striking confabulations. Most accounts of the cause of confabulations are cognitive, though the literature has produced anecdotal suggestions that confabulations may not be emotionally neutral, having a ('wish-fulfilment') bias that shapes the patient's perception of reality in a more affectively positive direction. The present study reviewed every case (N = 16) of false beliefs about place reported in the neuroscientific literature from 1980 to 2000, with blind raters evaluating the 'pleasantness' of the patient's actual and confabulated locations. In each case the confabulated location was evaluated as more pleasant. This striking finding supports the claim that there may be a systematic affective bias in the false beliefs held by neurological patients with confabulation. PMID:15223194

  17. ON THE LOW FALSE POSITIVE PROBABILITIES OF KEPLER PLANET CANDIDATES

    SciTech Connect

    Morton, Timothy D.; Johnson, John Asher E-mail: johnjohn@astro.caltech.edu

    2011-09-10

    We present a framework to conservatively estimate the probability that any particular planet-like transit signal observed by the Kepler mission is in fact a planet, prior to any ground-based follow-up efforts. We use Monte Carlo methods based on stellar population synthesis and Galactic structure models, and report false positive probabilities (FPPs) for every Kepler Object of Interest, assuming a 20% intrinsic occurrence rate of close-in planets in the radius range 0.5 R{sub +} < R{sub p} < 20 R{sub +}. Nearly 90% of the 1235 candidates have FPP <10%, and over half have FPP <5%. This probability varies with the magnitude and Galactic latitude of the target star, and with the depth of the transit signal-deeper signals generally have higher FPPs than shallower signals. We establish that a single deep high-resolution image will be an effective follow-up tool for the shallowest (Earth-sized) transits, providing the quickest route toward probabilistically validating the smallest candidates by potentially decreasing the FPP of an Earth-sized transit around a faint star from >10% to <1%. Since Kepler has detected many more planetary signals than can be positively confirmed with ground-based follow-up efforts in the near term, these calculations will be crucial to using the ensemble of Kepler data to determine population characteristics of planetary systems. We also describe how our analysis complements the Kepler team's more detailed BLENDER false positive analysis for planet validation.

  18. "False Positive" Claims of Near-Death Experiences and "False Negative" Denials of Near-Death Experiences

    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…

  19. Court revises suit arising from false-positive test result.

    PubMed

    1999-02-19

    The Texas Court of Appeals reinstated a portion of a lawsuit filed by [name removed], who was denied life insurance coverage following a false-positive HIV test. [Name removed] was denied coverage without explanation and was notified by the Houston Health Department a few weeks later that he was HIV-positive. He was retested several times, with each test being negative. A Harris County (TX) trial court had ruled a summary judgement against all claims, but the appeals court held that he might have a case based on the State's Deceptive Trade Practices Act. The appeals court did not allow him to recover damages based on negligence, but said that he could proceed with his claim of intentional infliction of emotional distress.

  20. Mitigating false-positive associations in rare disease gene discovery.

    PubMed

    Akle, Sebastian; Chun, Sung; Jordan, Daniel M; Cassa, Christopher A

    2015-10-01

    Clinical sequencing is expanding, but causal variants are still not identified in the majority of cases. These unsolved cases can aid in gene discovery when individuals with similar phenotypes are identified in systems such as the Matchmaker Exchange. We describe risks for gene discovery in this growing set of unsolved cases. In a set of rare disease cases with the same phenotype, it is not difficult to find two individuals with the same phenotype that carry variants in the same gene. We quantify the risk of false-positive association in a cohort of individuals with the same phenotype, using the prior probability of observing a variant in each gene from over 60,000 individuals (Exome Aggregation Consortium). Based on the number of individuals with a genic variant, cohort size, specific gene, and mode of inheritance, we calculate a P value that the match represents a true association. A match in two of 10 patients in MECP2 is statistically significant (P = 0.0014), whereas a match in TTN would not reach significance, as expected (P > 0.999). Finally, we analyze the probability of matching in clinical exome cases to estimate the number of cases needed to identify genes related to different disorders. We offer Rare Disease Match, an online tool to mitigate the uncertainty of false-positive associations. PMID:26378430

  1. Mitigating false-positive associations in rare disease gene discovery.

    PubMed

    Akle, Sebastian; Chun, Sung; Jordan, Daniel M; Cassa, Christopher A

    2015-10-01

    Clinical sequencing is expanding, but causal variants are still not identified in the majority of cases. These unsolved cases can aid in gene discovery when individuals with similar phenotypes are identified in systems such as the Matchmaker Exchange. We describe risks for gene discovery in this growing set of unsolved cases. In a set of rare disease cases with the same phenotype, it is not difficult to find two individuals with the same phenotype that carry variants in the same gene. We quantify the risk of false-positive association in a cohort of individuals with the same phenotype, using the prior probability of observing a variant in each gene from over 60,000 individuals (Exome Aggregation Consortium). Based on the number of individuals with a genic variant, cohort size, specific gene, and mode of inheritance, we calculate a P value that the match represents a true association. A match in two of 10 patients in MECP2 is statistically significant (P = 0.0014), whereas a match in TTN would not reach significance, as expected (P > 0.999). Finally, we analyze the probability of matching in clinical exome cases to estimate the number of cases needed to identify genes related to different disorders. We offer Rare Disease Match, an online tool to mitigate the uncertainty of false-positive associations.

  2. THE XO PLANETARY SURVEY PROJECT: ASTROPHYSICAL FALSE POSITIVES

    SciTech Connect

    Poleski, Radosaw; McCullough, Peter R.; Valenti, Jeff A.; Burke, Christopher J.; Machalek, Pavel; Janes, Kenneth

    2010-07-15

    Searches for planetary transits find many astrophysical false positives as a by-product. There are four main types analyzed in the literature: a grazing-incidence eclipsing binary (EB) star, an EB star with a small radius companion star, a blend of one or more stars with an unrelated EB star, and a physical triple star system. We present a list of 69 astrophysical false positives that had been identified as candidates of transiting planets of the on-going XO survey. This list may be useful in order to avoid redundant observation and characterization of these particular candidates that have been independently identified by other wide-field searches for transiting planets. The list may be useful for those modeling the yield of the XO survey and surveys similar to it. Subsequent observations of some of the listed stars may improve mass-radius relations, especially for low-mass stars. From the candidates exhibiting eclipses, we report three new spectroscopic double-line binaries and give mass function estimations for 15 single-line spectroscopic binaries.

  3. False positivity of gamma-glutamyl transpeptidase measurement in urine.

    PubMed

    Crivellenti, Leandro Zuccolotto; Mesa, Javier Sousa; Meirelles, Adriana Érica Wilkes Burton; Borin Crivellenti, Sofia; Mireya, Edna Gomes; Canola, Julio Carlos; Hatayde, Mário Roberto; Santana, Aureo Evangelista; Dantas, Márcio; Silva, Gyl Eanes Barros

    2014-05-01

    Although enzymuria tends to be associated to renal injury, there are no studies that have evaluated the presence of the enzyme gamma-glutamyl transpeptidase (GGT) spectrophotometry in the urine using a non-nephrotoxic agent (Nerium oleander) in order to evaluate the possibility of false positive results. The urinary GGT/urinary creatinine concentration ratio (uGGT/uCr) of 10 healthy dogs was calculated and posteriorly confronted with data from clinical evaluation, hematological and serum biochemical profiles, creatinine clearance (CrC), urinalysis, urine protein/creatinine ratio (UPC), electrocardiogram, systemic blood pressure (SBP) and light and electron microscopy. The results for kidney histology, SBP, UPC and CrC were not significantly different in any of the time-points analyzed. However, uGGT/uCr was significantly higher when measured 4 hours and 24 hours after administration of N. oleander. The measurement of the urinary GGT enzyme, as performed in many studies, yielded false positive results in dogs poisoned by a non-nephrotoxic agent.

  4. DSM-5, psychiatric epidemiology and the false positives problem.

    PubMed

    Wakefield, J C

    2015-06-01

    The revision effort leading to the publication of the fifth edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-5) was flawed in process, goals and outcome. The revision process suffered from lack of an adequate public record of the rationale for changes, thus shortchanging future scholarship. The goals, such as dimensionalising diagnosis, incorporating biomarkers and separating impairment from diagnosis, were ill-considered and mostly abandoned. However, DSM-5's greatest problem, and the target of the most vigorous and sustained criticism, was its failure to take seriously the false positives problem. By expanding diagnosis beyond plausible boundaries in ways inconsistent with DSM-5's own definition of disorder, DSM-5 threatened the validity of psychiatric research, including especially psychiatric epidemiology. I present four examples: increasing the symptom options while decreasing the diagnostic threshold for substance use disorder, elimination of the bereavement exclusion from major depression, allowing verbal arguments as evidence of intermittent explosive disorder and expanding attention-deficit/hyperactivity disorder to adults before addressing its manifest false positives problems. PMID:25675983

  5. Decoy Methods for Assessing False Positives and False Discovery Rates in Shotgun Proteomics

    PubMed Central

    Wang, Guanghui; Wu, Wells W.; Zhang, Zheng; Masilamani, Shyama; Shen, Rong-Fong

    2008-01-01

    The potential of getting a significant number of false positives (FPs) in peptide-spectrum matches (PSMs) obtained by proteomic database search has been well-recognized. Among the attempts to assess FPs, the concomitant use of target and decoy databases is widely practiced. By adjusting filtering criteria, FPs and false discovery rate (FDR) can be controlled at a desired level. Although the target-decoy approach is gaining in popularity, subtle differences in decoy construction (e.g., reversing vs. stochastic methods), rate calculation (e.g., total vs. unique PSMs), or searching (separate vs. composite) do exist among various implementations. In the present study, we evaluated the effects of these differences on FP and FDR estimations using a rat kidney protein sample and the SEQUEST search engine as an example. On the effects of decoy construction, we found that, when a single scoring filter (XCorr) was used, stochastic methods generated a higher estimation of FPs and FDR than sequence reversing methods, likely due to an increase in unique peptides. This higher estimation could largely be attenuated by creating decoy databases similar in effective size, but not by a simple normalization with a unique-peptide coefficient. When multiple filters were applied, the differences seen between reversing and stochastic methods significantly diminished, suggesting multiple filterings reduce the dependency on how a decoy is constructed. For a fixed set of filtering criteria, FDR and FPs estimated by using unique PSMs were almost twice those using total PSMs. The higher estimation seemed to be dependent on data acquisition setup. As to the differences between performing separate or composite searches, in general, FDR estimated from separate search was about three times that from composite search. The degree of difference gradually decreased as the filtering criteria became more stringent. Paradoxically, the estimated true positives in separate search were higher when multiple

  6. Decoy methods for assessing false positives and false discovery rates in shotgun proteomics.

    PubMed

    Wang, Guanghui; Wu, Wells W; Zhang, Zheng; Masilamani, Shyama; Shen, Rong-Fong

    2009-01-01

    The potential of getting a significant number of false positives (FPs) in peptide-spectrum matches (PSMs) obtained by proteomic database search has been well-recognized. Among the attempts to assess FPs, the concomitant use of target and decoy databases is widely practiced. By adjusting filtering criteria, FPs and false discovery rate (FDR) can be controlled at a desired level. Although the target-decoy approach is gaining in popularity, subtle differences in decoy construction (e.g., reversing vs stochastic methods), rate calculation (e.g., total vs unique PSMs), or searching (separate vs composite) do exist among various implementations. In the present study, we evaluated the effects of these differences on FP and FDR estimations using a rat kidney protein sample and the SEQUEST search engine as an example. On the effects of decoy construction, we found that, when a single scoring filter (XCorr) was used, stochastic methods generated a higher estimation of FPs and FDR than sequence reversing methods, likely due to an increase in unique peptides. This higher estimation could largely be attenuated by creating decoy databases similar in effective size but not by a simple normalization with a unique-peptide coefficient. When multiple filters were applied, the differences seen between reversing and stochastic methods significantly diminished, suggesting multiple filterings reduce the dependency on how a decoy is constructed. For a fixed set of filtering criteria, FDR and FPs estimated by using unique PSMs were almost twice those using total PSMs. The higher estimation seemed to be dependent on data acquisition setup. As to the differences between performing separate or composite searches, in general, FDR estimated from the separate search was about three times that from the composite search. The degree of difference gradually decreased as the filtering criteria became more stringent. Paradoxically, the estimated true positives in separate search were higher when

  7. Accurate decisions in an uncertain world: collective cognition increases true positives while decreasing false positives

    PubMed Central

    Wolf, Max; Kurvers, Ralf H. J. M.; Ward, Ashley J. W.; Krause, Stefan; Krause, Jens

    2013-01-01

    In a wide range of contexts, including predator avoidance, medical decision-making and security screening, decision accuracy is fundamentally constrained by the trade-off between true and false positives. Increased true positives are possible only at the cost of increased false positives; conversely, decreased false positives are associated with decreased true positives. We use an integrated theoretical and experimental approach to show that a group of decision-makers can overcome this basic limitation. Using a mathematical model, we show that a simple quorum decision rule enables individuals in groups to simultaneously increase true positives and decrease false positives. The results from a predator-detection experiment that we performed with humans are in line with these predictions: (i) after observing the choices of the other group members, individuals both increase true positives and decrease false positives, (ii) this effect gets stronger as group size increases, (iii) individuals use a quorum threshold set between the average true- and false-positive rates of the other group members, and (iv) individuals adjust their quorum adaptively to the performance of the group. Our results have broad implications for our understanding of the ecology and evolution of group-living animals and lend themselves for applications in the human domain such as the design of improved screening methods in medical, forensic, security and business applications. PMID:23407830

  8. "False positive" claims of near-death experiences and "false negative" denials of near-death experiences.

    PubMed

    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 research and in psychiatric outpatients. The frequency of false positives and negatives varied in samples that differed in prevalence of, and knowledge about, NDEs. The influence of participants' knowledge about NDEs on the findings of near-death research makes it critically important to use standardized criteria for identifying NDEs.

  9. Controlling false positives in the mapping of epistatic QTL.

    PubMed

    Wei, W-H; Knott, S; Haley, C S; de Koning, D-J

    2010-04-01

    This study addresses the poorly explored issue of the control of false positive rate (FPR) in the mapping of pair-wise epistatic quantitative trait loci (QTL). A nested test framework was developed to (1) allow pre-identified QTL to be used directly to detect epistasis in one-dimensional genome scans, (2) to detect novel epistatic QTL pairs in two-dimensional genome scans and (3) to derive genome-wide thresholds through permutation and handle multiple testing. We used large-scale simulations to evaluate the performance of both the one- and two-dimensional approaches in mapping different forms and levels of epistasis and to generate profiles of FPR, power and accuracy to inform epistasis mapping studies. We showed that the nested test framework and genome-wide thresholds were essential to control FPR at the 5% level. The one-dimensional approach was generally more powerful than the two-dimensional approach in detecting QTL-associated epistasis and identified nearly all epistatic pairs detected from the two-dimensional approach. However, only the two-dimensional approach could detect epistatic QTL with weak main effects. Combining the two approaches allowed effective mapping of different forms of epistasis, whereas using the nested test framework kept the FPR under control. This approach provides a good search engine for high-throughput epistasis analyses.

  10. Polio vaccines, SV40 and human tumours, an update on false positive and false negative results.

    PubMed

    Elmishad, A G; Bocchetta, M; Pass, H I; Carbone, M

    2006-01-01

    Simian virus 40 (SV40) has been detected in different human tumours in numerous laboratories. The detection of SV40 in human tumours has been linked to the administration of SV40-contaminated polio vaccines from 1954 until 1963. Many of these reports linked SV40 to human mesothelioma. Some studies have failed to detect SV40 in human tumours and this has caused a controversy. Here we review the current literature. Moreover, we present evidence showing how differences in the sensitivities of methodologies can lead to a very different interpretation of the same study. The same 20 mesothelioma specimens all tested negative, 2/20 tested positive or 7/20 tested positive for SV40 Tag by simply changing the detection method on the same immuno-precipitation/western blot membranes. These results provide a simple explanation for some of the apparent discordant results reported in the literature.

  11. False-positive indium-111 labeled leukocyte scintigram in a patient with a painful hip prosthesis

    SciTech Connect

    Feldman, N.; Makler, P.T. Jr.; Alavi, A.

    1986-01-01

    A Tronzo hip prosthesis is designed to elicit an inflammatory reaction in order to promote prosthesis stability. A three-phased bone scan and Ga-67 imaging in conjunction with physical examination and laboratory findings failed to demonstrate evidence for osteomyelitis in a patient with a painful hip prosthesis, in whom images obtained with In-111-labeled leukocytes were positive. This observation demonstrated that the interpretation of the latter technique in demonstrating inflammation can cause a false impression of an infectious process.

  12. False Positive Lyme Disease IgM Immunoblots in Children.

    PubMed

    Lantos, Paul M; Lipsett, Susan C; Nigrovic, Lise E

    2016-07-01

    In our cross-sectional sample of 7289 serologic tests for Lyme disease, we identified 167 instances of a positive IgM immunoblot but a negative IgG immunoblot test result. Considering that only 71% (95% CI 64%-78%) of patients had Lyme disease, a positive IgM immunoblot alone should be interpreted with caution to avoid over-diagnosis of Lyme disease.

  13. Quantification of false positives within Moon Zoo crater annotations

    NASA Astrophysics Data System (ADS)

    Tar, P.; Thacker, N.

    2014-04-01

    The Moon Zoo citizen science project [1] allows members of the public to annotate lunar images, providing researchers with a wealth of location and size information regarding the population of small craters on the Moon. To date, approximately 4 million images have been inspected. Here, we show how a quantitative pattern recognition system can be used to estimate the quantity of contamination in Moon Zoo data from erroneous annotations. The proposed method produces not only estimates of true verses false crater annotations, but also a full error covariance, with additional conformity checks, which is essential for the meaningful interpretation of measurements, e.g. for plotting error bars.

  14. Unusual false-positive case of urinary screening for buprenorphine.

    PubMed

    Lippi, Giuseppe; Romero, Araelsis; Cervellin, Gianfranco; Mercadanti, Mariella

    2011-01-01

    Buprenorphine is a centrally acting analgesic drug that is administered for the management of opioid dependence and as an analgesic drug for the treatment of chronic pain. The growing use of this substance has determined an increased need for laboratory testing for either detection and confirmation of the illicit use or monitoring compliance as a substitution therapy for opioid dependence. We describe here the case of urinary sample adulteration with exogenous buprenorphine (6,952 ng/ml), which has led to afalse-positive immunoassay test result (14.9 ng/ml) on a subsequent sample due to a phenomenon of instrumental carry-over. This unusual case confirms the importance to take into account adulteration when screening urines for buprenorphine in patients undergoing substitution therapy for opioid dependence, routinely perform a confirmation assay on positive samples, and rule out instrumental carry-over. PMID:21786326

  15. Positive reaction to allergen (image)

    MedlinePlus

    Allergic reaction is a sensitivity to a specific substance, called an allergen, that is contacted through the skin, inhaled into the lungs, swallowed or injected. The body's reaction to an allergen can be mild, such as ...

  16. Sensitization to petrolatum: an unusual cause of false-positive drug patch-tests.

    PubMed

    Ulrich, G; Schmutz, J L; Trechot, Ph; Commun, N; Barbaud, A

    2004-09-01

    We report on an unexpected sensitization to petrolatum diagnosed with the occurrence of multiple nonrelevant and false-positive drug patch-tests performed while investigating a patient suffering from many cutaneous adverse drug reactions. All the positive drug patch-tests were prepared with GILBERT vaseline. This petrolatum reaction is positive as it was tested with five other brands of petrolatums a few months later. As the same petrolatums, but from different batches were tested, patch-tests with GILBERT petrolatum were doubtful, while other petrolatums were positive. White petrolatum is a mixture of semisolid hydrocarbons of the methane series. The sensitizing impurities of petrolatum are polycyclic aromatic hydrocarbons, e.g. phenanthrene derivatives. The purity of petrolatum depends on both the petroleum stock and on the production and packaging methods. Even if rare, contact sensitization to petrolatum can disturb the interpretation of drug patch-tests. It is necessary in the interpretation of drug patch-tests to test both in petrolatum and other vehicles and with all the different petrolatums used in preparing the material for drug patch-tests. So, it is essential to advise the patients sensitized to petrolatum to remove all the topical drugs, such as all the cosmetics, which contain petrolatum in their formulation.

  17. NMR-based quality control approach for the identification of false positives and false negatives in high throughput screening.

    PubMed

    Dalvit, Claudio; Caronni, Dannica; Mongelli, Nicola; Veronesi, Marina; Vulpetti, Anna

    2006-06-01

    The quality of the data generated in a high throughput screening (HTS) run is fundamental for selecting bona fide inhibitors and for ensuring the capture of the full richness of inhibitors present in a chemical library. For this purpose a quality control filter based on three one dimensional (1D) proton NMR experiments is proposed. The approach called SPAM (Solubility, Purity and Aggregation of the Molecule) Filter requires the acquisition of a 1D reference spectrum, a WaterLOGSY spectrum and/or a selective longitudinal relaxation filter spectrum for the identified hits dissolved in aqueous solution and in the presence of a water soluble reference molecule. This palette of experiments permits the rapid characterization of the identity, purity, solubility and aggregation state of the active compound. This knowledge is crucial for deriving accurate IC(50) and K(1) values of the inhibitors, for identifying false negatives and for detecting promiscuous inhibitors. Only compounds that pass through the SPAM Filter can be considered as starting points for medicinal chemistry efforts directed toward lead optimization. Examples of this approach in the identification of false positives in a screening run against the enzyme thymidine phosphorylase (TP) and the rescue of a false negative in a screening run against the Ser/Thr kinase AKT1 are presented. PMID:16925519

  18. CT colonography with computer-aided detection: recognizing the causes of false-positive reader results.

    PubMed

    Trilisky, Igor; Wroblewski, Kristen; Vannier, Michael W; Horne, John M; Dachman, Abraham H

    2014-01-01

    Computed tomography (CT) colonography is a screening modality used to detect colonic polyps before they progress to colorectal cancer. Computer-aided detection (CAD) is designed to decrease errors of detection by finding and displaying polyp candidates for evaluation by the reader. CT colonography CAD false-positive results are common and have numerous causes. The relative frequency of CAD false-positive results and their effect on reader performance on the basis of a 19-reader, 100-case trial shows that the vast majority of CAD false-positive results were dismissed by readers. Many CAD false-positive results are easily disregarded, including those that result from coarse mucosa, reconstruction, peristalsis, motion, streak artifacts, diverticulum, rectal tubes, and lipomas. CAD false-positive results caused by haustral folds, extracolonic candidates, diminutive lesions (<6 mm), anal papillae, internal hemorrhoids, varices, extrinsic compression, and flexural pseudotumors are almost always recognized and disregarded. The ileocecal valve and tagged stool are common sources of CAD false-positive results associated with reader false-positive results. Nondismissable CAD soft-tissue polyp candidates larger than 6 mm are another common cause of reader false-positive results that may lead to further evaluation with follow-up CT colonography or optical colonoscopy. Strategies for correctly evaluating CAD polyp candidates are important to avoid pitfalls from common sources of CAD false-positive results.

  19. False positives observed on the Seratec® PSA SemiQuant Cassette Test with condom lubricants.

    PubMed

    Bitner, Sara E

    2012-11-01

    In the course of the validation of a new component of the prostate-specific antigen (PSA) SemiQuant Cassette Test marketed by Seratec(®) , a false-positive reaction was observed when testing samples collected from the surface of unused, lubricated condoms. A variety of personal lubricants and condoms were tested to determine the frequency of the false positive, as well as its potential source. Samples were extracted in both water and the manufacturer-provided buffer, and the test was performed according to the manufacturer's suggested protocol. The false positive was observed intermittently, but occurred consistently with samples containing nonoxynol-9, a strong detergent utilized as a spermicide. The reaction may be attributable to the combination of latex and nonoxynol-9. Because of the unreliability of the test to confirm the presence of PSA in samples collected from condoms, the PSA cassette is an unsuitable method for confirming the presence of seminal fluid in condoms. PMID:22494324

  20. False Positive Radioiodinated Metaiodobenzylguanidine ((123)I-MIBG) Uptake in Undifferentiated Adrenal Malignant Tumor.

    PubMed

    Jung, Hee Soo; Moon, Seok Jun; Kim, Yun Mi; Kang, Hye Rim; Lee, Seok Mo; Jung, Soo Jin; Choi, Seok Jin; Kim, Tae Kyoon; Kwon, Min Jeong; Park, Jeong Hyun; Lee, Soon Hee

    2015-01-01

    (123)I-Metaiodobenzylguanidine ((123)I-MIBG) scintigraphy is a widely used functional imaging tool with a high degree of sensitivity and specificity in diagnosis of pheochromocytoma. However, rare cases of false positive reactions have been reported. A 67-year-old male patient was admitted with epigastric pain. Abdominal computed tomography (CT) revealed a heterogeneous left adrenal mass 6 cm in diameter; following hormone testing, (123)I-MIBG scintigraphy was performed to determine the presence of pheochromocytoma, which confirmed eccentric uptake by a large left adrenal gland mass. Chest CT and PET-CT confirmed metastatic lymphadenopathy; therefore, endobronchial ultrasound transbronchial needle aspiration was performed. Metastatic carcinoma of unknown origin was suspected from a lymph node biopsy, and surgical resection was performed for definitive diagnosis and correction of excess hormonal secretion. A final diagnosis of undifferentiated adrenal malignant tumor was rendered, instead of histologically malignant pheochromocytoma, despite the uptake of (123)I-MIBG demonstrated by scintigraphy.

  1. Statistical approaches to account for false-positive errors in environmental DNA samples.

    PubMed

    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.

  2. PMA treatment is an effective means to reduce false positive PCR testing results

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Traditional and real time PCR are widely used in detecting bacterial pathogens in various food matrix and environmental samples. Sometimes a positive detection using PCR can not be confirmed by subsequent culture isolation of the targeted pathogen, resulting in a potential “false positive.” False po...

  3. Addressing False Positives in Early Reading Assessment Using Intervention Response Data

    ERIC Educational Resources Information Center

    McAlenney, Athena Lentini; Coyne, Michael D.

    2015-01-01

    The current study examined a solution to high false positive reading risk classification rates in early kindergarten by investigating a method of identifying students with possible false positive risk classifications and returning them to general classroom instruction. Researchers assessed kindergarten students (N = 105) identified as at risk who…

  4. Consequences of a false-positive mammography result: drug consumption before and after screening.

    PubMed

    von Euler-Chelpin, My; Bæksted, Christina; Vejborg, Ilse; Lynge, Elsebeth

    2016-05-01

    Background Previous research showed women experiencing false-positive mammograms to have greater anxiety about breast cancer than women with normal mammograms. To elucidate psychological effects of false-positive mammograms, we studied impact on drug intake. Methods We calculated the ratio of drug use for women with false-positive versus women with normal mammograms, before and after the event, using population-based registers, 1997-2006. The ratio of the ratios (RRR) assessed the impact. Results Before the test, 40.3% of women from the false-positive group versus 36.2% from the normal group used anxiolytic and antidepressant drugs. There was no difference in use of beta blockers. Hormone therapy was used more frequently by the false-positive, 36.6% versus 28.7%. The proportion of women using anxiolytic and antidepressant drugs increased with 19% from the before to the after period in the false-positive group, and with 16% in the normal group, resulting in an RRR of 1.02 (95% CI 0.92-1.14). RRR was 1.03 for beta blockers, 0.97 for hormone therapy. Conclusion(s) Drugs used to mitigate mood disorders were used more frequently by women with false-positive than by women with normal mammograms already before the screening event, while the changes from before to after screening were similar for both groups. The results point to the importance of control for potential selection in studies of screening effects.

  5. Experimental investigation of false positive errors in auditory species occurrence surveys

    USGS Publications Warehouse

    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

  6. Experimental investigation of false positive errors in auditory species occurrence surveys.

    PubMed

    Miller, David A W; Weir, Linda A; Mcclintock, Brett T; Grant, Evan H Campbell; Bailey, Larissa L; Simons, Theodore R

    2012-07-01

    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, who 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

  7. Reducing false positive incidental findings with ensemble genotyping and logistic regression-based variant filtering methods

    PubMed Central

    Hwang, Kyu-Baek; Lee, In-Hee; Park, Jin-Ho; Hambuch, Tina; Choi, Yongjoon; Kim, MinHyeok; Lee, Kyungjoon; Song, Taemin; Neu, Matthew B.; Gupta, Neha; Kohane, Isaac S.; Green, Robert C.; Kong, Sek Won

    2014-01-01

    As whole genome sequencing (WGS) uncovers variants associated with rare and common diseases, an immediate challenge is to minimize false positive findings due to sequencing and variant calling errors. False positives can be reduced by combining results from orthogonal sequencing methods, but costly. Here we present variant filtering approaches using logistic regression (LR) and ensemble genotyping to minimize false positives without sacrificing sensitivity. We evaluated the methods using paired WGS datasets of an extended family prepared using two sequencing platforms and a validated set of variants in NA12878. Using LR or ensemble genotyping based filtering, false negative rates were significantly reduced by 1.1- to 17.8-fold at the same levels of false discovery rates (5.4% for heterozygous and 4.5% for homozygous SNVs; 30.0% for heterozygous and 18.7% for homozygous insertions; 25.2% for heterozygous and 16.6% for homozygous deletions) compared to the filtering based on genotype quality scores. Moreover, ensemble genotyping excluded > 98% (105,080 of 107,167) of false positives while retaining > 95% (897 of 937) of true positives in de novo mutation (DNM) discovery, and performed better than a consensus method using two sequencing platforms. Our proposed methods were effective in prioritizing phenotype-associated variants, and ensemble genotyping would be essential to minimize false positive DNM candidates. PMID:24829188

  8. False-positive interferences of common urine drug screen immunoassays: a review.

    PubMed

    Saitman, Alec; Park, Hyung-Doo; Fitzgerald, Robert L

    2014-09-01

    Urine drug screen (UDS) immunoassays are a quick and inexpensive method for determining the presence of drugs of abuse. Many cross-reactivities exist with other analytes, potentially causing a false-positive result in an initial drug screen. Knowledge of these potential interferents is important in determining a course of action for patient care. We present an inclusive review of analytes causing false-positive interferences with drugs-of-abuse UDS immunoassays, which covers the literature from the year 2000 to present. English language articles were searched via the SciFinder platform with the strings 'false positive [drug] urine' yielding 173 articles. These articles were then carefully analyzed and condensed to 62 that included data on causes of false-positive results. The discussion is separated into six sections by drug class with a corresponding table of cross-reacting compounds for quick reference. False-positive results were described for amphetamines, opiates, benzodiazepines, cannabinoids, tricyclic antidepressants, phencyclidine, lysergic acid diethylamide and barbiturates. These false-positive results support the generally accepted practice that immunoassay positive results are considered presumptive until confirmed by a second independent chemical technique.

  9. False-positive interferences of common urine drug screen immunoassays: a review.

    PubMed

    Saitman, Alec; Park, Hyung-Doo; Fitzgerald, Robert L

    2014-09-01

    Urine drug screen (UDS) immunoassays are a quick and inexpensive method for determining the presence of drugs of abuse. Many cross-reactivities exist with other analytes, potentially causing a false-positive result in an initial drug screen. Knowledge of these potential interferents is important in determining a course of action for patient care. We present an inclusive review of analytes causing false-positive interferences with drugs-of-abuse UDS immunoassays, which covers the literature from the year 2000 to present. English language articles were searched via the SciFinder platform with the strings 'false positive [drug] urine' yielding 173 articles. These articles were then carefully analyzed and condensed to 62 that included data on causes of false-positive results. The discussion is separated into six sections by drug class with a corresponding table of cross-reacting compounds for quick reference. False-positive results were described for amphetamines, opiates, benzodiazepines, cannabinoids, tricyclic antidepressants, phencyclidine, lysergic acid diethylamide and barbiturates. These false-positive results support the generally accepted practice that immunoassay positive results are considered presumptive until confirmed by a second independent chemical technique. PMID:24986836

  10. Accounting for false-positive acoustic detections of bats using occupancy models

    USGS Publications Warehouse

    Clement, Matthew J.; Rodhouse, Thomas J.; Ormsbee, Patricia C.; Szewczak, Joseph M.; Nichols, James D.

    2014-01-01

    4. Synthesis and applications. Our results suggest that false positives sufficient to affect inferences may be common in acoustic surveys for bats. We demonstrate an approach that can estimate occupancy, regardless of the false-positive rate, when acoustic surveys are paired with capture surveys. Applications of this approach include monitoring the spread of White-Nose Syndrome, estimating the impact of climate change and informing conservation listing decisions. We calculate a site-specific probability of occupancy, conditional on survey results, which could inform local permitting decisions, such as for wind energy projects. More generally, the magnitude of false positives suggests that false-positive occupancy models can improve accuracy in research and monitoring of bats and provide wildlife managers with more reliable information.

  11. Risk of breast cancer after false-positive results in mammographic screening.

    PubMed

    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.

  12. Congenital absence of the gallbladder: another cause of false-positive hepatobiliary image

    SciTech Connect

    Dickinson, C.Z.; Powers, T.A.; Sandler, M.P.; Partain, C.L.

    1984-01-01

    Hepatobiliary imaging with the various technetium-labeled IDA compounds is more than 90% sensitive and specific for the diagnosis of acute cholecystitis. Causes of false-positive studies include chronic cholecystitis, cystic-duct obstruction by tumor, prolonged fasting, the nonfasting state, pancreatitis, alcoholism, parenteral hyperalimentation, and severe intercurrent illness. A case of congenital absence of the gallbladder is sumbitted as another cause of a false-positive scan.

  13. Is there a positive bias in false recognition? Evidence from confabulating amnesia patients.

    PubMed

    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.

  14. Prospective assessment of the false positive rate of the Australian snake venom detection kit in healthy human samples.

    PubMed

    Nimorakiotakis, Vasilios Bill; Winkel, Kenneth D

    2016-03-01

    The Snake Venom Detection Kit (SVDK; bioCSL Pty Ltd, Australia) distinguishes venom from the five most medically significant snake immunotypes found in Australia. This study assesses the rate of false positives that, by definition, refers to a positive assay finding in a sample from someone who has not been bitten by a venomous snake. Control unbroken skin swabs, simulated bite swabs and urine specimens were collected from 61 healthy adult volunteers [33 males and 28 females] for assessment. In all controls, simulated bite site and urine samples [a total of 183 tests], the positive control well reacted strongly within one minute and no test wells reacted during the ten minute incubation period. However, in two urine tests, the negative control well gave a positive reaction (indicating an uninterpretable test). A 95% confidence interval for the false positive rate, on a per-patient rate, derived from the findings of this study, would extend from 0% to 6% and, on a per-test basis, it would be 0-2%. It appears to be a very low incidence (0-6%) of intrinsic true false positives for the SVDK. The clinical impresssion of a high SVDK false positive rate may be mostly related to operator error.

  15. Constraining the false positive rate for Kepler planet candidates with multicolour photometry from the GTC

    NASA Astrophysics Data System (ADS)

    Colón, Knicole D.; Ford, Eric B.; Morehead, Robert C.

    2012-10-01

    Using the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) instrument installed on the 10.4-m Gran Telescopio Canarias (GTC), we acquired multicolour transit photometry of four small (Rp≲5 R⊕) short-period (P ≲ 6 d) planet candidates recently identified by the Kepler space mission. These observations are part of a programme to constrain the false positive rate for small, short-period Kepler planet candidates. Since planetary transits should be largely achromatic when observed at different wavelengths (excluding the small colour changes due to stellar limb darkening), we use the observed transit colour to identify candidates as either false positives (e.g. a blend with a stellar eclipsing binary either in the background/foreground or bound to the target star) or validated planets. Our results include the identification of KOI 225.01 and KOI 1187.01 as false positives and the tentative validation of KOI 420.01 and KOI 526.01 as planets. The probability of identifying two false positives out of a sample of four targets is less than 1 per cent, assuming an overall false positive rate for Kepler planet candidates of 10 per cent (as estimated by Morton & Johnson). Therefore, these results suggest a higher false positive rate for the small, short-period Kepler planet candidates than has been theoretically predicted by other studies which consider the Kepler planet candidate sample as a whole. Furthermore, our results are consistent with a recent Doppler study of short-period giant Kepler planet candidates. We also investigate how the false positive rate for our sample varies with different planetary and stellar properties. Our results suggest that the false positive rate varies significantly with orbital period and is largest at the shortest orbital periods (P < 3 d), where there is a corresponding rise in the number of detached eclipsing binary stars (i.e. systems that can easily mimic planetary transits) that have been discovered by

  16. Investigation of False Positive Results with an Oral Fluid Rapid HIV-1/2 Antibody Test

    PubMed Central

    Jafa, Krishna; Patel, Pragna; MacKellar, Duncan A.; Sullivan, Patrick S.; Delaney, Kevin P.; Sides, Tracy L.; Newman, Alexandra P.; Paul, Sindy M.; Cadoff, Evan M.; Martin, Eugene G.; Keenan, Patrick A.; Branson, Bernard M.

    2007-01-01

    Background In March 2004, the OraQuick® rapid HIV antibody test became the first rapid HIV test approved by the US Food and Drug Administration for use on oral fluid specimens. Test results are available in 20 minutes, and the oral fluid test is non-invasive. From August 2004–June 2005, we investigated a sudden increase in false-positive results occurring in a performance study of OraQuick® oral-fluid rapid HIV tests in Minnesota. Methodology/Principal Findings In a field investigation, we reviewed performance study data on oral-fluid and whole-blood OraQuick® rapid HIV test device lots and expiration dates and assessed test performance and interpretation with oral-fluid and whole-blood specimens by operators who reported false-positive results. We used multivariate logistic regression to evaluate client demographic and risk characteristics associated with false-positive results. Next, we conducted an incidence study of false-positive OraQuick rapid HIV tests in nine US cities and tested both oral-fluid and finger-stick whole-blood specimens from clients; reactive tests were confirmed with Western blot. Sixteen (4.1%) false-positive oral-fluid results occurred in the performance study from April 15, 2004 through August 31, 2004 with unexpired devices from six test lots among 388 HIV-uninfected clients (specificity, 95.9%; 95% CI: 93.4–97.6). Three test operators who had reported false-positive results performed and interpreted the test according to package-insert instructions. In multivariate analysis, only older age was significantly associated with false-positive results (adjusted odds ratio = 4.5, 95% CI: 1.2–25.7). In the incidence study, all valid oral-fluid and whole-blood results from 2,268 clients were concordant and no false-positive results occurred (100% specificity). Conclusions/Significance The field investigation did not identify a cause for the increase in false-positive oral-fluid results, and the incidence study detected no false-positive

  17. False-positive scalp activity in 131I imaging associated with hair coloring.

    PubMed

    Yan, Di; Doss, Mohan; Mehra, Ranee; Parsons, Rosaleen B; Milestone, Barton N; Yu, Jian Q

    2013-03-01

    A patient with metastatic papillary thyroid carcinoma (after surgical resection of tumor and positive lymph nodes) undergoing thyroid ablation therapy with (131)I is described. Whole-body scintigraphy was performed 1 wk after ablation therapy to evaluate the presence of residual disease. The whole-body images demonstrated an artifact caused by tracer accumulation in the patient's scalp related to recent hair coloring. Common etiologies of false-positive (131)I scintigraphic findings are briefly reviewed. The importance of taking preventative measures to decrease the number of false-positive findings and recognizing these findings when they occur is discussed.

  18. False positive results for antibody to HIV in two men with systemic lupus erythematosus.

    PubMed Central

    Esteva, M H; Blasini, A M; Ogly, D; Rodríguez, M A

    1992-01-01

    False positive results were obtained for HIV tests in two men with active systemic lupus erythematosus (SLE) who were suspected of being infected with HIV because of fever, weight loss, lymphadenopathy, and inflammatory myopathy. Enzyme linked immunosorbent assays (ELISAs) for HIV were twice positive when tested three times over a period of six months. Western blot analysis showed reactivity against the gp41 band in patient 1. False positive results for HIV tests can occur in patients with SLE, potentially leading to an erroneous diagnosis of HIV infection. PMID:1417140

  19. Metal Impurities Cause False Positives in High-Throughput Screening Campaigns

    PubMed Central

    2012-01-01

    Organic impurities in compound libraries are known to often cause false-positive signals in screening campaigns for new leads, but organic impurities do not fully account for all false-positive results. We discovered inorganic impurities in our screening library that can also cause positive signals for a variety of targets and/or readout systems, including biochemical and biosensor assays. We investigated in depth the example of zinc for a specific project and in retrospect in various HTS screens at Roche and propose a straightforward counter screen using the chelator TPEN to rule out inhibition caused by zinc. PMID:24900642

  20. False-positive Chlamydiazyme results during urine sediment analysis due to bacterial urinary tract infections.

    PubMed Central

    Demaio, J; Boyd, R S; Rensi, R; Clark, A

    1991-01-01

    Our study examined whether urinary tract infections (UTIs) would cause false-positive results when urine sediment was tested with the Chlamydiazyme (CZ) system. Thirty-six infected urine samples and fifteen controls were studied. All controls were negative. Forty-seven percent of Escherichia coli UTIs (n = 30) and 100% of Klebsiella pneumoniae UTIs (n = 4) were positive on CZ testing of urine sediment. Nine E. coli UTIs positive by CZ were negative by direct fluorescent-antibody staining. When suspensions of the pure cultures were analyzed, 47% of E. coli and 100% of K. pneumoniae samples were CZ positive. False-positive results were not related to organism biotype or urine characteristics, including pH, specific gravity, and leukocyte count. We conclude that the presence of a UTI and also bacterial contamination must be ruled out prior to urine sediment testing. PMID:1885739

  1. False-positive buprenorphine EIA urine toxicology results due to high dose morphine: a case report.

    PubMed

    Tenore, Peter L

    2012-01-01

    In monitoring a patient with chronic pain who was taking high-dose morphine and oxycodone with weekly urine enzymatic immunoassay (EIA) toxicology testing, the authors noted consistent positives for buprenorphine. The patient was not taking buprenorphine, and gas chromatography/mass spectroscopy (GCMS) testing on multiple samples revealed no buprenorphine, indicating a case of false-positive buprenorphine EIAs in a high-dose opiate case. The authors discontinued oxycodone for a period of time and then discontinued morphine. Urine monitoring with EIAs and GCMS revealed false-positive buprenorphine EIAs, which remained only when the patient was taking morphine. When taking only oxycodone and no morphine, urine samples became buprenorphine negative. When morphine was reintroduced, false-positive buprenorphine results resumed. Medical practitioners should be aware that high-dose morphine (with morphine urine levels turning positive within the 15,000 to 28,000 mg/mL range) may produce false-positive buprenorphine EIAs with standard urine EIA toxicology testing.

  2. Case Reports of Aripiprazole Causing False-Positive Urine Amphetamine Drug Screens in Children.

    PubMed

    Kaplan, Justin; Shah, Pooja; Faley, Brian; Siegel, Mark E

    2015-12-01

    Urine drug screens (UDSs) are used to identify the presence of certain medications. One limitation of UDSs is the potential for false-positive results caused by cross-reactivity with other substances. Amphetamines have an extensive list of cross-reacting medications. The literature contains reports of false-positive amphetamine UDSs with multiple antidepressants and antipsychotics. We present 2 cases of presumed false-positive UDSs for amphetamines after ingestion of aripiprazole. Case 1 was a 16-month-old girl who accidently ingested 15 to 45 mg of aripiprazole. She was lethargic and ataxic at home with 1 episode of vomiting containing no identifiable tablets. She remained sluggish with periods of irritability and was admitted for observation. UDS on 2 consecutive days came back positive for amphetamines. Case 2 was of a 20-month-old girl who was brought into the hospital after accidental ingestion of an unknown quantity of her father's medications which included aripiprazole. UDS on the first day of admission came back positive only for amphetamines. Confirmatory testing with gas chromatography-mass spectrometry (GC-MS) on the blood and urine samples were also performed for both patients on presentation to detect amphetamines and were subsequently negative. Both patients returned to baseline and were discharged from the hospital. To our knowledge, these cases represent the first reports of false-positive amphetamine urine drug tests with aripiprazole. In both cases, aripiprazole was the drug with the highest likelihood of causing the positive amphetamine screen. The implications of these false-positives include the possibility of unnecessary treatment and monitoring of patients.

  3. False-positive urine phencyclidine immunoassay screen result caused by interference by tramadol and its metabolites.

    PubMed

    Ly, Binh T; Thornton, Stephen L; Buono, Colleen; Stone, Judith A; Wu, Alan H B

    2012-06-01

    Phencyclidine is one of the drugs of abuse included in qualitative urine drug screens that are frequently ordered in the emergency department despite concerns about specificity and clinical utility. Many drugs have been described to cause false-positive results for phencyclidine. We present 2 cases of false-positive phencyclidine qualitative urine drug screen results in patients with seizures from tramadol misuse or abuse. The involvement of tramadol and its active metabolite, N-desmethyltramadol, was confirmed by in vitro testing. These cases illustrate that tramadol and its metabolites can trigger a false-positive phencyclidine urine drug screen result in nonfatal cases and highlight the lack of specificity of the phencyclidine qualitative urine drug screen.

  4. Potential for false positive HIV test results with the serial rapid HIV testing algorithm

    PubMed Central

    2012-01-01

    Background Rapid HIV tests provide same-day results and are widely used in HIV testing programs in areas with limited personnel and laboratory infrastructure. The Uganda Ministry of Health currently recommends the serial rapid testing algorithm with Determine, STAT-PAK, and Uni-Gold for diagnosis of HIV infection. Using this algorithm, individuals who test positive on Determine, negative to STAT-PAK and positive to Uni-Gold are reported as HIV positive. We conducted further testing on this subgroup of samples using qualitative DNA PCR to assess the potential for false positive tests in this situation. Results Of the 3388 individuals who were tested, 984 were HIV positive on two consecutive tests, and 29 were considered positive by a tiebreaker (positive on Determine, negative on STAT-PAK, and positive on Uni-Gold). However, when the 29 samples were further tested using qualitative DNA PCR, 14 (48.2%) were HIV negative. Conclusion Although this study was not primarily designed to assess the validity of rapid HIV tests and thus only a subset of the samples were retested, the findings show a potential for false positive HIV results in the subset of individuals who test positive when a tiebreaker test is used in serial testing. These findings highlight a need for confirmatory testing for this category of individuals. PMID:22429706

  5. Sestamibi scintigraphy for parathyroid localisation: a reminder of the dangers of false positives.

    PubMed

    Whitcroft, Katherine Lisa; Sharma, Anup

    2014-03-11

    Surgical parathyroidectomy is the only curative treatment for primary hyperparathyroidism. As minimally invasive parathyroidectomy increases in popularity, so does reliance on preoperative parathyroid localisation techniques. One such technique is sestamibi scintigraphy. We report a case of false-positive sestamibi scintigraphy caused by follicular variant of papillary thyroid carcinoma. Subsequent completion thyroidectomy was not possible due to widespread postoperative fibrosis. This case, therefore, highlights the potential dangers of false-positive results due to thyroid carcinoma and encourages surgeons to consider this possibility when faced with intrathyroidal or otherwise ambiguous parathyroid localisation results.

  6. False positive diagnosis on (131)iodine whole-body scintigraphy of differentiated thyroid cancers.

    PubMed

    Triggiani, Vincenzo; Giagulli, Vito Angelo; Iovino, Michele; De Pergola, Giovanni; Licchelli, Brunella; Varraso, Antonio; Dicembrino, Franca; Valle, Guido; Guastamacchia, Edoardo

    2016-09-01

    (131)Iodine is used both to ablate any residual thyroid tissue or metastatic disease and to obtain whole-body diagnostic images after total thyroidectomy for differentiated thyroid cancer (DTC). Even though whole-body scan is highly accurate in showing thyroid residues as well as metastases of DTC, false positive results can be found, possibly leading to diagnostic errors and unnecessary treatments. This paper reviews the physiological and pathological processes involved as well as the strategy to recognize and rule out false positive radioiodine images.

  7. Does replication groups scoring reduce false positive rate in SNP interaction discovery?

    PubMed Central

    2010-01-01

    Background Computational methods that infer single nucleotide polymorphism (SNP) interactions from phenotype data may uncover new biological mechanisms in non-Mendelian diseases. However, practical aspects of such analysis face many problems. Present experimental studies typically use SNP arrays with hundreds of thousands of SNPs but record only hundreds of samples. Candidate SNP pairs inferred by interaction analysis may include a high proportion of false positives. Recently, Gayan et al. (2008) proposed to reduce the number of false positives by combining results of interaction analysis performed on subsets of data (replication groups), rather than analyzing the entire data set directly. If performing as hypothesized, replication groups scoring could improve interaction analysis and also any type of feature ranking and selection procedure in systems biology. Because Gayan et al. do not compare their approach to the standard interaction analysis techniques, we here investigate if replication groups indeed reduce the number of reported false positive interactions. Results A set of simulated and false interaction-imputed experimental SNP data sets were used to compare the inference of SNP-SNP interactions by means of replication groups to the standard approach where the entire data set was directly used to score all candidate SNP pairs. In all our experiments, the inference of interactions from the entire data set (e.g. without using the replication groups) reported fewer false positives. Conclusions With respect to the direct scoring approach the utility of replication groups does not reduce false positive rates, and may, depending on the data set, often perform worse. PMID:20092660

  8. Indium-111 labeled leukocyte uptake: false-positive results in noninfected pseudoaneurysms

    SciTech Connect

    Gilbert, B.R.; Cerqueira, M.D.; Vea, H.W.; Nelp, W.B.

    1986-03-01

    Indium-111 (In-111) leukocyte scintigraphy was performed in two patients with postsurgical pseudoaneurysms as part of preoperative evaluation for evidence of graft infection. Despite positive In-111 uptake by the pseudoaneurysms, surgical and pathologic examinations failed to reveal any evidence of infection. The most likely explanation for the false-positive results is the labeling of contaminating platelets and erythrocytes in the leukocyte mixture. Caution must be exercised in interpretation of In-111 leukocyte scans in patients with postsurgical pseudoaneurysms.

  9. EMPLOYING TOPOGRAPHICAL HEIGHT MAP IN COLONIC POLYP MEASUREMENT AND FALSE POSITIVE REDUCTION

    PubMed Central

    Yao, Jianhua; Li, Jiang; Summers, Ronald M.

    2008-01-01

    CT Colonography (CTC) is an emerging minimally invasive technique for screening and diagnosing colon cancers. Computer Aided Detection (CAD) techniques can increase sensitivity and reduce false positives. Inspired by the way radiologists detect polyps via 3D virtual fly-through in CTC, we borrowed the idea from geographic information systems to employ topographical height map in colonic polyp measurement and false positive reduction. After a curvature based filtering and a 3D CT feature classifier, a height map is computed for each detection using a ray-casting algorithm. We design a concentric index to characterize the concentric pattern in polyp height map based on the fact that polyps are protrusions from the colon wall and round in shape. The height map is optimized through a multi-scale spiral spherical search to maximize the concentric index. We derive several topographic features from the map and compute texture features based on wavelet decomposition. We then send the features to a committee of support vector machines for classification. We have trained our method on 394 patients (71 polyps) and tested it on 792 patients (226 polyps). Results showed that we can achieve 95% sensitivity at 2.4 false positives per patient and the height map features can reduce false positives by more than 50%. We compute the polyp height and width measurements and correlate them with manual measurements. The Pearson correlations are 0.74 (p=0.11) and 0.75 (p=0.17) for height and width, respectively. PMID:19578483

  10. False Positives in Multiple Regression: Unanticipated Consequences of Measurement Error in the Predictor Variables

    ERIC Educational Resources Information Center

    Shear, Benjamin R.; Zumbo, Bruno D.

    2013-01-01

    Type I error rates in multiple regression, and hence the chance for false positive research findings, can be drastically inflated when multiple regression models are used to analyze data that contain random measurement error. This article shows the potential for inflated Type I error rates in commonly encountered scenarios and provides new…

  11. Are False-Positive Rates Leading to an Overestimation of Noise-Induced Hearing Loss?

    ERIC Educational Resources Information Center

    Schlauch, Robert S.; Carney, Edward

    2011-01-01

    Purpose: To estimate false-positive rates for rules proposed to identify early noise-induced hearing loss (NIHL) using the presence of notches in audiograms. Method: Audiograms collected from school-age children in a national survey of health and nutrition (the Third National Health and Nutrition Examination Survey [NHANES III]; National Center…

  12. Erythromycin hepatotoxicity. A rare cause of a false-positive technetium-99m DISIDA study

    SciTech Connect

    Swayne, L.C.; Kolc, J.

    1986-01-01

    An unusual cause of a cholescintigraphic, false-positive, erythromycin-induced hepatotoxicity is presented. This occurred in the presence of preservation of hepatic uptake and the normal appearance of gut activity. Serial scintigraphy and serum chemistries documented underlying gallbladder normalcy.

  13. IS HCI THAT IS USED AS A PRESERVATIVE CREATING FALSE POSITIVES FOR TBA IN GROUND WATER

    EPA Science Inventory

    Will hydrochloric acid produce false positives for TBA? Yes, if you heat the sample to get a lower detection limit for TBA. Conventional purge and trap methods at ambient temperature have a reporting limit for TBA between 50 and 100 g/liter. This is higher than the provisiona...

  14. Cumulative Incidence of False-Positive Results in Repeated, Multimodal Cancer Screening

    PubMed Central

    Croswell, Jennifer Miller; Kramer, Barnett S.; Kreimer, Aimee R.; Prorok, Phil C.; Xu, Jian-Lun; Baker, Stuart G.; Fagerstrom, Richard; Riley, Thomas L.; Clapp, Jonathan D.; Berg, Christine D.; Gohagan, John K.; Andriole, Gerald L.; Chia, David; Church, Timothy R.; Crawford, E. David; Fouad, Mona N.; Gelmann, Edward P.; Lamerato, Lois; Reding, Douglas J.; Schoen, Robert E.

    2009-01-01

    PURPOSE Multiple cancer screening tests have been advocated for the general population; however, clinicians and patients are not always well-informed of screening burdens. We sought to determine the cumulative risk of a false-positive screening result and the resulting risk of a diagnostic procedure for an individual participating in a multimodal cancer screening program. METHODS Data were analyzed from the intervention arm of the ongoing Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, a randomized controlled trial to determine the effects of prostate, lung, colorectal, and ovarian cancer screening on disease-specific mortality. The 68,436 participants, aged 55 to 74 years, were randomized to screening or usual care. Women received serial serum tests to detect cancer antigen 125 (CA-125), transvaginal sonograms, posteroanterior-view chest radiographs, and flexible sigmoidoscopies. Men received serial chest radiographs, flexible sigmoidoscopies, digital rectal examinations, and serum prostate-specific antigen tests. Fourteen screening examinations for each sex were possible during the 3-year screening period. RESULTS After 14 tests, the cumulative risk of having at least 1 false-positive screening test is 60.4% (95% CI, 59.8%–61.0%) for men, and 48.8% (95% CI, 48.1%–49.4%) for women. The cumulative risk after 14 tests of undergoing an invasive diagnostic procedure prompted by a false-positive test is 28.5% (CI, 27.8%–29.3%) for men and 22.1% (95% CI, 21.4%–22.7%) for women. CONCLUSIONS For an individual in a multimodal cancer screening trial, the risk of a false-positive finding is about 50% or greater by the 14th test. Physicians should educate patients about the likelihood of false positives and resulting diagnostic interventions when counseling about cancer screening. PMID:19433838

  15. New Constraints on the False Positive Rate for Short-Period Kepler Planet Candidates

    NASA Astrophysics Data System (ADS)

    Colón, Knicole D.; Morehead, Robert C.; Ford, Eric B.

    2015-01-01

    The Kepler space mission has discovered thousands of potential planets orbiting other stars, thereby setting the stage for in-depth studies of different populations of planets. We present new multi-wavelength transit photometry of small (Rp < 6 Earth radii), short-period (P < 6 days) Kepler planet candidates acquired with the Gran Telescopio Canarias. Multi-wavelength transit photometry allows us to search for wavelength-dependent transit depths and subsequently identify eclipsing binary false positives (which are especially prevalent at the shortest orbital periods). We combine these new observations of three candidates with previous results for five other candidates (Colón & Ford 2011 and Colón, Ford, & Morehead 2012) to provide new constraints on the false positive rate for small, close-in candidates. In our full sample, we identify four candidates as viable planets and four as eclipsing binary false positives. We therefore find a higher false positive rate for small, close-in candidates compared to the lower false positive rate of ~10% determined by other studies for the full sample of Kepler planet candidates (e.g. Fressin et al. 2013). We also discuss the dearth of known planets with periods less than ~2.5 days and radii between ~3 and 11 Earth radii (the so-called 'sub-Jovian desert'), since the majority of the candidates in our study are located in or around this 'desert.' The lack of planets with these orbital and physical properties is not expected to be due to observational bias, as short-period planets are generally easier to detect (especially if they are larger or more massive than Earth). We consider the implications of our results for the other ~20 Kepler planet candidates located in this desert. Characterizing these candidates will allow us to better understand the formation processes of this apparently rare class of planets.

  16. Decisions to shoot in a weapon identification task: The influence of cultural stereotypes and perceived threat on false positive errors.

    PubMed

    Fleming, Kevin K; Bandy, Carole L; Kimble, Matthew O

    2010-01-01

    The decision to shoot a gun engages executive control processes that can be biased by cultural stereotypes and perceived threat. The neural locus of the decision to shoot is likely to be found in the anterior cingulate cortex (ACC), where cognition and affect converge. Male military cadets at Norwich University (N=37) performed a weapon identification task in which they made rapid decisions to shoot when images of guns appeared briefly on a computer screen. Reaction times, error rates, and electroencephalogram (EEG) activity were recorded. Cadets reacted more quickly and accurately when guns were primed by images of Middle-Eastern males wearing traditional clothing. However, cadets also made more false positive errors when tools were primed by these images. Error-related negativity (ERN) was measured for each response. Deeper ERNs were found in the medial-frontal cortex following false positive responses. Cadets who made fewer errors also produced deeper ERNs, indicating stronger executive control. Pupil size was used to measure autonomic arousal related to perceived threat. Images of Middle-Eastern males in traditional clothing produced larger pupil sizes. An image of Osama bin Laden induced the largest pupil size, as would be predicted for the exemplar of Middle East terrorism. Cadets who showed greater increases in pupil size also made more false positive errors. Regression analyses were performed to evaluate predictions based on current models of perceived threat, stereotype activation, and cognitive control. Measures of pupil size (perceived threat) and ERN (cognitive control) explained significant proportions of the variance in false positive errors to Middle-Eastern males in traditional clothing, while measures of reaction time, signal detection response bias, and stimulus discriminability explained most of the remaining variance. PMID:19813139

  17. Decisions to Shoot in a Weapon Identification Task: The Influence of Cultural Stereotypes and Perceived Threat on False Positive Errors

    PubMed Central

    Fleming, Kevin K.; Bandy, Carole L.; Kimble, Matthew O.

    2014-01-01

    The decision to shoot engages executive control processes that can be biased by cultural stereotypes and perceived threat. The neural locus of the decision to shoot is likely to be found in the anterior cingulate cortex (ACC) where cognition and affect converge. Male military cadets at Norwich University (N=37) performed a weapon identification task in which they made rapid decisions to shoot when images of guns appeared briefly on a computer screen. Reaction times, error rates, and EEG activity were recorded. Cadets reacted more quickly and accurately when guns were primed by images of middle-eastern males wearing traditional clothing. However, cadets also made more false positive errors when tools were primed by these images. Error-related negativity (ERN) was measured for each response. Deeper ERN’s were found in the medial-frontal cortex following false positive responses. Cadets who made fewer errors also produced deeper ERN’s, indicating stronger executive control. Pupil size was used to measure autonomic arousal related to perceived threat. Images of middle-eastern males in traditional clothing produced larger pupil sizes. An image of Osama bin Laden induced the largest pupil size, as would be predicted for the exemplar of Middle East terrorism. Cadets who showed greater increases in pupil size also made more false positive errors. Regression analyses were performed to evaluate predictions based on current models of perceived threat, stereotype activation, and cognitive control. Measures of pupil size (perceived threat) and ERN (cognitive control) explained significant proportions of the variance in false positive errors to middle-eastern males in traditional clothing, while measures of reaction time, signal detection response bias, and stimulus discriminability explained most of the remaining variance. PMID:19813139

  18. [False positive serum des-gamma-carboxy prothrombin after resection of hepatocellular carcinoma].

    PubMed

    Hiramatsu, Kumiko; Tanaka, Yasuhito; Takagi, Kazumi; Iida, Takayasu; Takasaka, Yoshimitsu; Mizokami, Masashi

    2007-04-01

    Measurements of serum concentrations of des-gamma-carboxy-prothrombin (PIVKA-II) are widely used for diagnosing hepatocellular carcinoma (HCC). Recently, when we evaluated the correlation of PIVKA-II between two commercially available PIVKA-II immunoassay kits (Lumipulse f vs. Picolumi) to introduce it in our hospital, false high values of PIVKA-II were observed in Lumipulse assay. Four(4%) of 100 serum samples showed false high values, and all of them were obtained from patients less than 2 month after curative resection of HCC. Examining additional 7 patients with HCC resection, serum samples from the 5 patients had the same trend. To elucidate the non-specific reaction by Lumipulse assay which utilized alkaline phosphatase (ALP) enzymatic reaction, inhibition assays by various absorbents such as inactive ALP and IgM antibodies were performed. Excess of inactive ALP reduced the high values of PIVKA-II. Note that anti-bleeding sheets (fibrinogen combined drug), which included bovine thrombin, were directly attached on liver of all patients with HCC resection in this study. As the sheets also contaminate ALP and probably produce IgM antibodies to ALP, the IgM may cross-react with anti-PIVKA-II antibodies directly. Taken together, it was suggested that produced antibodies against ALP derived from anti-bleeding sheets led false high values of PIVKA-II in the patients with HCC resection.

  19. Risk of Breast Cancer in Women with False-Positive Results according to Mammographic Features.

    PubMed

    Castells, Xavier; Torá-Rocamora, Isabel; Posso, Margarita; Román, Marta; Vernet-Tomas, Maria; Rodríguez-Arana, Ana; Domingo, Laia; Vidal, Carmen; Baré, Marisa; Ferrer, Joana; Quintana, María Jesús; Sánchez, Mar; Natal, Carmen; Espinàs, Josep A; Saladié, Francina; Sala, María

    2016-08-01

    Purpose To assess the risk of breast cancer in women with false-positive screening results according to radiologic classification of mammographic features. Materials and Methods Review board approval was obtained, with waiver of informed consent. This retrospective cohort study included 521 200 women aged 50-69 years who underwent screening as part of the Spanish Breast Cancer Screening Program between 1994 and 2010 and who were observed until December 2012. Cox proportional hazards regression analysis was used to estimate the age-adjusted hazard ratio (HR) of breast cancer and the 95% confidence interval (CI) in women with false-positive mammograms as compared with women with negative mammograms. Separate models were adjusted for screen-detected and interval cancers and for screen-film and digital mammography. Time without a breast cancer diagnosis was plotted by using Kaplan-Meier curves. Results When compared with women with negative mammograms, the age-adjusted HR of cancer in women with false-positive results was 1.84 (95% CI: 1.73, 1.95; P < .001). The risk was higher in women who had calcifications, whether they were (HR, 2.73; 95% CI: 2.28, 3.28; P < .001) or were not (HR, 2.24; 95% CI: 2.02, 2.48; P < .001) associated with masses. Women in whom mammographic features showed changes in subsequent false-positive results were those who had the highest risk (HR, 9.13; 95% CI: 8.28, 10.07; P < .001). Conclusion Women with false-positive results had an increased risk of breast cancer, particularly women who had calcifications at mammography. Women who had more than one examination with false-positive findings and in whom the mammographic features changed over time had a highly increased risk of breast cancer. Previous mammographic features might yield useful information for further risk-prediction models and personalized follow-up screening protocols. (©) RSNA, 2016 Online supplemental material is available for this article.

  20. False-positive tests for syphilis associated with human immunodeficiency virus and hepatitis B virus infection among intravenous drug abusers. Valencian Study Group on HIV Epidemiology.

    PubMed

    Hernández-Aguado, I; Bolumar, F; Moreno, R; Pardo, F J; Torres, N; Belda, J; Espacio, A

    1998-11-01

    The role of HIV, hepatitis C virus, and hepatitis B virus infections in the production of biological false-positive reactions for syphilis was evaluated in two large samples of intravenous drug abusers and homosexual men attending AIDS prevention centers in Spain. A significantly increased odds ratio (OR) for false-positive tests for syphilis [OR 2.23, 95% confidence intervals (CI) 1.76-2.83] was observed for HIV-seropositive intravenous drug abusers; biological false-positive reactions were also more frequent (OR 1.73, 95% CI 1.30-2.31) among intravenous drug abusers who were hepatitis B virus seropositive but not among those who were hepatitis C virus seropositive (OR 0.90; 95% CI 0.48-1.69). Among homosexuals, the association between HIV and biological false-positive reactions was restricted to subjects who were also intravenous drug abusers, indicating the crucial role of intravenous drug abuse. Only 20.5% of intravenous drug abusers with a previous biological false-positive reaction yielded a false-positive result in their subsequent visit.

  1. Modeling false positive detections in species occurrence data under different study designs.

    PubMed

    Chambert, Thierry; Miller, David A W; Nichols, James D

    2015-02-01

    The occurrence of false positive detections in presence-absence data, even when they occur infrequently, can lead to severe bias when estimating species occupancy patterns. Building upon previous efforts to account for this source of observational error, we established a general framework to model false positives in occupancy studies and extend existing modeling approaches to encompass a broader range of sampling designs. Specifically, we identified three common sampling designs that are likely to cover most scenarios encountered by researchers. The different designs all included ambiguous detections, as well as some known-truth data, but their modeling differed in the level of the model hierarchy at which the known-truth information was incorporated (site level or observation level). For each model, we provide the likelihood, as well as R and BUGS code needed for implementation. We also establish a clear terminology and provide guidance to help choosing the most appropriate design and modeling approach.

  2. False positive reduction in mammographic mass detection using local binary patterns.

    PubMed

    Oliver, Arnau; Lladó, Xavier; Freixenet, Jordi; Martí, Joan

    2007-01-01

    In this paper we propose a new approach for false positive reduction in the field of mammographic mass detection. The goal is to distinguish between the true recognized masses and the ones which actually are normal parenchyma. Our proposal is based on Local Binary Patterns (LBP) for representing salient micro-patterns and preserving at the same time the spatial structure of the masses. Once the descriptors are extracted, Support Vector Machines (SVM) are used for classifying the detected masses. We test our proposal using a set of 1792 suspicious regions of interest extracted from the DDSM database. Exhaustive experiments illustrate that LBP features are effective and efficient for false positive reduction even at different mass sizes, a critical aspect in mass detection systems. Moreover, we compare our proposal with current methods showing that LBP obtains better performance. PMID:18051070

  3. Chromosomes Emission of Planet Candidate Host Stars: A Way to Identify False Positives

    NASA Astrophysics Data System (ADS)

    Karoff, Christoffer; Albrecht, Simon; Bonanno, Alfio; Faurschou Knudsen, Mads

    2016-10-01

    It has been hypothesized that the presence of closely orbiting giant planets is associated with enhanced chromospheric emission of their host stars. The main cause for such a relation would likely be enhanced dynamo action induced by the planet. We present measurements of chromospheric emission in 234 planet candidate systems from the Kepler mission. This ensemble includes 37 systems with giant-planet candidates, which show a clear emission enhancement. The enhancement, however, disappears when systems that are also identified as eclipsing binary candidates are removed from the ensemble. This suggests that a large fraction of the giant-planet candidate systems with chromospheric emission stronger than the Sun are not giant-planet systems, but false positives. Such false-positive systems could be tidally interacting binaries with strong chromospheric emission. This hypothesis is supported by an analysis of 188 eclipsing binary candidates that show increasing chromospheric emission as function of decreasing orbital period.

  4. False-positive elimination for computer-aided detection of pulmonary micronodules

    NASA Astrophysics Data System (ADS)

    Chang, Sukmoon; Zhou, Jinghao; Metaxas, Dimitris N.; Axel, Leon

    2006-03-01

    Computed Tomography (CT) is generally accepted as the most sensitive way for lung cancer screening. Its high contrast resolution allows the detection of small nodules and, thus, lung cancer at a very early stage. Due to the amount of data it produces, however, automating the nodule detection process is viable. The challenging problem for any nodule detection system is to keep low false-positive detection rate while maintaining high sensitivity. In this paper, we first describe a 3D filter-based method for pulmonary micronodule detection from high-resolution 3D chest CT images. Then, we propose a false-positive elimination method based on a deformable model. Finally, we present promising results of applying our method to various clinical chest CT datasets with over 90% detection rate. The proposed method focuses on the automatic detection of both calcified (high-contrast) and noncalcified (low-contrast) granulomatous nodules less than 5mm in diameter.

  5. Frontal sinus accuracy in identification as measured by false positives in kin groups.

    PubMed

    Cameriere, Roberto; Ferrante, Luigi; Molleson, Theya; Brown, Barry

    2008-11-01

    The aims of this study were to verify if frontal sinuses can uniquely identify individuals belonging to family groups using Cameriere methods and to test if kinship can affect the proportion of erroneous identifications. For this purpose, we compared the proportion of false-positive identifications in a sample of 99 individuals within 20 families with a control sample of 98 other individuals without kinship. The results show that the combined use of SOR and the Yoshino code number allows personal identification with a small probability of false positives (p < 10(-6)), even when kinship is taken into account. The present research confirms the importance of studying anthropological frameworks for identification, which leads to reliable methods and allows for both quick and economic procedures.

  6. Heterophilic antibodies interfering with radioimmunoassay. A false-positive pregnancy test

    SciTech Connect

    Vladutiu, A.O.; Sulewski, J.M.; Pudlak, K.A.; Stull, C.G.

    1982-11-19

    A young woman with amenorrhea had a consistently positive pregnancy test result (serum radioimmunoassay measurement of ..beta..-human chorionic gonadotropin hormone). No fetal or placental tissue was found after uterine curettage and exploratory laparotomy. The false-positive pregnancy test result was due to heterophilic antibovine and antigoat antibodies in the patient's serum. These antibodies interfered with radioimmunoassays using goat antibodies. This case shows that serum heterophilic antibodies can interfere with immunoassays and result in unnecessary diagnostic procedures and/or unnecessary treatment.

  7. False-positive focused abdominal sonography in trauma in a hypotensive child: case report.

    PubMed

    Imamedjian, Isabelle; Baird, Robert; Dubrovsky, Alexander Sasha

    2015-06-01

    We report a case of a false-positive focused abdominal sonography in trauma (FAST) examination in a persistently hypotensive pediatric trauma patient, performed 12 hours after the trauma, suspected to be caused by massive fluid resuscitation leading to ascites. While a positive FAST in a hypotensive trauma patient usually indicates hemoperitoneum, this case illustrates that the timing of the FAST examination relative to the injury, as well as clinical evolution including the volume of fluid resuscitation, need to be considered when interpreting the results of serial and/or late FAST examinations. PMID:26035503

  8. False-positive ethanol blood concentrations leading to clinical confusion on Christmas Day.

    PubMed

    Jones, Terry E

    2011-11-01

    A case of altered consciousness in which ethanol ingestion was one of the differential diagnoses is described. Three separate blood samples were conveyed to the hospital biochemistry laboratory and each returned a positive value when assayed via an indirect, enzymatic method. The family strongly denied alcohol ingestion and hence, a few days later, the samples were conveyed to an external laboratory using a 'specific', chromatographic method. These samples were all reported as negative for ethanol. Alternative causes of altered consciousness were restricted by the false-positive ethanol laboratory results.

  9. Using Spitzer to Estimate the Kepler False Positive Rate and to Validate Kepler Candidates.

    NASA Astrophysics Data System (ADS)

    Desert, Jean-Michel; Charbonneau, D.; Fressin, F.; Torres, G.

    2012-01-01

    I present the results from an ongoing large campaign with the Spitzer Space Telescope to gather near-infrared photometric measurements of Kepler Objects of Interest (KOI). Our goals are (1) to validate the planetary status of these Kepler candidates, (2) to estimate observationally the false positive rate, and (3) to study the atmospheres of confirmed planets through measurements of their secondary eclipses. Our target list spans of wide range of candidate sizes and periods orbiting various spectral type stars. The Spitzer observations provide constraints on the possibility of astrophysical false positives resulting from stellar blends, including eclipsing binaries and hierarchical triples. The number of possible blends per star is estimated using stellar population synthesis models and observational probes of the KOI close environments from direct imaging (e.g. Adaptive Optics, Speckle images, Kepler centroids). Combining all the above information with the shape of the transit lightcurves from the Kepler photometry, we compute odd ratios for the 34 candidates we observed in order to determine their false positive probability. Our results suggest that the Kepler false positive rate in this subset of candidates is low. I finally present a new list of Kepler candidates that we were able to validate using this method. This work is based on observations made with the Spitzer, which is operated by JPL/Caltech, under a contract with NASA. Support was provided by NASA through an award issued by JPL/Caltech. Kepler was selected as the 10th mission of the Discovery Program. Funding for this mission is provided by NASA, Science Mission Directorate.

  10. Rate and nature of false positives in the CoRoT exoplanet search

    NASA Astrophysics Data System (ADS)

    Almenara, J. M.; Deeg, H. J.; Aigrain, S.; Alonso, R.; Auvergne, M.; Baglin, A.; Barbieri, M.; Barge, P.; Bordé, P.; Bouchy, F.; Bruntt, H.; Cabrera, J.; Carone, L.; Carpano, S.; Catala, C.; Csizmadia, Sz.; de La Reza, R.; Deleuil, M.; Dvorak, R.; Erikson, A.; Fridlund, M.; Gandolfi, D.; Gillon, M.; Gondoin, P.; Guenther, E.; Guillot, T.; Hatzes, A.; Hébrard, G.; Jorda, L.; Lammer, H.; Léger, A.; Llebaria, A.; Loeillet, B.; Magain, P.; Mayor, M.; Mazeh, T.; Moutou, C.; Ollivier, M.; Pätzold, M.; Pont, F.; Queloz, D.; Rauer, H.; Régulo, C.; Renner, S.; Rouan, D.; Samuel, B.; Schneider, J.; Shporer, A.; Wuchterl, G.; Zucker, S.

    2009-10-01

    Context: The CoRoT satellite searches for planets by applying the transit method, monitoring up to 12 000 stars in the galactic plane for 150 days in each observing run. This search is contaminated by a large fraction of false positives, caused by different eclipsing binary configurations that might be confused with a transiting planet. Aims: We evaluate the rates and nature of false positives in the CoRoT exoplanets search and compare our results with semiempirical predictions. Methods: We consider the detected binary and planet candidates in the first three extended CoRoT runs, and classify the results of the follow-up observations completed to verify their planetary nature. We group the follow-up results into undiluted binaries, diluted binaries, and planets and compare their abundances with predictions from the literature. Results: 83% of the initial detections are classified as false positives using only the CoRoT light-curves, the remaining 17% require follow-up observations. Finally, 12% of the candidates in the follow-up program are planets. The shape of the overall distribution of the false positive rate follows previous predictions, except for candidates with transit depths below about 0.4%. For candidates with transit depths in the range from 0.1-0.4%, CoRoT detections are nearly complete, and this difference from predictions is probably real and dominated by a lower than expected abundance of diluted eclipsing binaries. The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil , ESA (RSSD and Science Programme), Germany and Spain.

  11. "Does replication groups scoring reduce false positive rate in SNP interaction discovery?: Response"

    PubMed Central

    2010-01-01

    A response to Toplak et al: Does replication groups scoring reduce false positive rate in SNP interaction discovery? BMC Genomics 2010, 11:58. Background The genomewide evaluation of genetic epistasis is a computationally demanding task, and a current challenge in Genetics. HFCC (Hypothesis-Free Clinical Cloning) is one of the methods that have been suggested for genomewide epistasis analysis. In order to perform an exhaustive search of epistasis, HFCC has implemented several tools and data filters, such as the use of multiple replication groups, and direction of effect and control filters. A recent article has claimed that the use of multiple replication groups (as implemented in HFCC) does not reduce the false positive rate, and we hereby try to clarify these issues. Results/Discussion HFCC uses, as an analysis strategy, the possibility of replicating findings in multiple replication groups, in order to select a liberal subset of preliminary results that are above a statistical criterion and consistent in direction of effect. We show that the use of replication groups and the direction filter reduces the false positive rate of a study, although at the expense of lowering the overall power of the study. A post-hoc analysis of these selected signals in the combined sample could then be performed to select the most promising results. Conclusion Replication of results in independent samples is generally used in scientific studies to establish credibility in a finding. Nonetheless, the combined analysis of several datasets is known to be a preferable and more powerful strategy for the selection of top signals. HFCC is a flexible and complete analysis tool, and one of its analysis options combines these two strategies: A preliminary multiple replication group analysis to eliminate inconsistent false positive results, and a post-hoc combined-group analysis to select the top signals. PMID:20576100

  12. False-positive reduction in mammography using multiscale spatial Weber law descriptor and support vector machines.

    PubMed

    Hussain, Muhammad

    2014-01-01

    In a CAD system for the detection of masses, segmentation of mammograms yields regions of interest (ROIs), which are not only true masses but also suspicious normal tissues that result in false positives. We introduce a new method for false-positive reduction in this paper. The key idea of our approach is to exploit the textural properties of mammograms and for texture description, to use Weber law descriptor (WLD), which outperforms state-of-the-art best texture descriptors. The basic WLD is a holistic descriptor by its construction because it integrates the local information content into a single histogram, which does not take into account the spatial locality of micropatterns. We extend it into a multiscale spatial WLD (MSWLD) that better characterizes the texture micro structures of masses by incorporating the spatial locality and scale of microstructures. The dimension of the feature space generated by MSWLD becomes high; it is reduced by selecting features based on their significance. Finally, support vector machines are employed to classify ROIs as true masses or normal parenchyma. The proposed approach is evaluated using 1024 ROIs taken from digital database for screening mammography and an accuracy of Az = 0.99 ± 0.003 (area under receiver operating characteristic curve) is obtained. A comparison reveals that the proposed method has significant improvement over the state-of-the-art best methods for false-positive reduction problem. PMID:24954976

  13. The trazodone metabolite meta-chlorophenylpiperazine can cause false-positive urine amphetamine immunoassay results.

    PubMed

    Baron, Jason M; Griggs, David A; Nixon, Andrea L; Long, William H; Flood, James G

    2011-07-01

    Amphetamines and methamphetamines are part of an important class of drugs included in most urine drugs of abuse screening panels, and a common assay to detect these drugs is the Amphetamines II immunoassay (Roche Diagnostics). To demonstrate that meta-chlorophenylpiperazine (m-CPP), a trazodone metabolite, cross-reacts in the Amphetamines II assay, we tested reference standards of m-CPP at various concentrations (200 to 20,000 g/L). We also tested real patient urine samples containing m-CPP (detected and quantified by HPLC) with no detectable amphetamine, methamphetamine, or MDMA (demonstrated by GC MS). In both the m-CPP standards and the patient urine samples, we found a strong association between m-CPP concentration and Amphetamines II immunoreactivity (r = 0.990 for the urine samples). Further, we found that patients taking trazodone can produce urine with sufficient m-CPP to result in false-positive Amphetamines II results. At our institution, false-positive amphetamine results occur not infrequently in patients taking trazodone with at least 8 trazodone-associated false-positive results during a single 26-day period. Laboratories should remain cognizant of this interference when interpreting results of this assay.

  14. Proteins interacting with cloning scars: a source of false positive protein-protein interactions.

    PubMed

    Banks, Charles A S; Boanca, Gina; Lee, Zachary T; Florens, Laurence; Washburn, Michael P

    2015-02-23

    A common approach for exploring the interactome, the network of protein-protein interactions in cells, uses a commercially available ORF library to express affinity tagged bait proteins; these can be expressed in cells and endogenous cellular proteins that copurify with the bait can be identified as putative interacting proteins using mass spectrometry. Control experiments can be used to limit false-positive results, but in many cases, there are still a surprising number of prey proteins that appear to copurify specifically with the bait. Here, we have identified one source of false-positive interactions in such studies. We have found that a combination of: 1) the variable sequence of the C-terminus of the bait with 2) a C-terminal valine "cloning scar" present in a commercially available ORF library, can in some cases create a peptide motif that results in the aberrant co-purification of endogenous cellular proteins. Control experiments may not identify false positives resulting from such artificial motifs, as aberrant binding depends on sequences that vary from one bait to another. It is possible that such cryptic protein binding might occur in other systems using affinity tagged proteins; this study highlights the importance of conducting careful follow-up studies where novel protein-protein interactions are suspected.

  15. False positives complicate ancient pathogen identifications using high-throughput shotgun sequencing

    PubMed Central

    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

  16. Postmortem urine immunoassay showing false-positive phencyclidine reactivity in a case of fatal tramadol overdose.

    PubMed

    Hull, Mindy J; Griggs, David; Knoepp, Stewart M; Smogorzewska, Agata; Nixon, Andrea; Flood, James G

    2006-12-01

    This is a report of postmortem false-positive reactivity using an enzyme-multiplied urine phencyclidine (PCP) immunoassay (EMIT II+) due to a single-agent fatal tramadol overdose. An autopsy of a 42-year-old male who died alone at home revealed no identifiable lethal anatomic abnormalities, thus leading to toxicologic analysis. Femoral blood was obtained for drug testing by high-performance liquid chromatography (HPLC) and showed a tramadol level of 14.0 mg/L, 2 orders of magnitude greater than the therapeutic range (0.1 to 0.3 mg/L). Urine was also obtained and EMIT II+ immunoassay revealed positivity for PCP at 88 mAU/min. However, confirmatory testing by HPLC failed to identify PCP in either the urine or serum. To verify the suspicion that this was a false-positive PCP result, stock solutions of tramadol and its major metabolite (O-desmethyltramadol) at concentrations of 100 mg/L in 10% methanol/H2O were compared with a blank solution (10% methanol/H2O) for EMIT II+ PCP reactivity and demonstrated reactivities of 44 mAU/min and 27 mAU/min, respectively. While these individual results were below the cutoff reactivity for a positive EMIT II+ PCP result (ca. 85 mAU/min), they were much more reactive than the blank calibrator (set at 0 mAU/min). Therefore, we conclude that the immunoreactivity of tramadol and its metabolites in aggregate is responsible for the PCP immunoassay interference and false-positive result.

  17. THE FALSE POSITIVE RATE OF KEPLER AND THE OCCURRENCE OF PLANETS

    SciTech Connect

    Fressin, Francois; Torres, Guillermo; Charbonneau, David; Dressing, Courtney D.; Bryson, Stephen T.; Christiansen, Jessie; Jenkins, Jon M.; Batalha, Natalie M.; Walkowicz, Lucianne M.

    2013-04-01

    The Kepler mission is uniquely suited to study the frequencies of extrasolar planets. This goal requires knowledge of the incidence of false positives such as eclipsing binaries in the background of the targets, or physically bound to them, which can mimic the photometric signal of a transiting planet. We perform numerical simulations of the Kepler targets and of physical companions or stars in the background to predict the occurrence of astrophysical false positives detectable by the mission. Using real noise level estimates, we compute the number and characteristics of detectable eclipsing pairs involving main-sequence stars and non-main-sequence stars or planets, and we quantify the fraction of those that would pass the Kepler candidate vetting procedure. By comparing their distribution with that of the Kepler Objects of Interest (KOIs) detected during the first six quarters of operation of the spacecraft, we infer the false positive rate of Kepler and study its dependence on spectral type, candidate planet size, and orbital period. We find that the global false positive rate of Kepler is 9.4%, peaking for giant planets (6-22 R{sub Circled-Plus }) at 17.7%, reaching a low of 6.7% for small Neptunes (2-4 R{sub Circled-Plus }), and increasing again for Earth-size planets (0.8-1.25 R{sub Circled-Plus }) to 12.3%. Most importantly, we also quantify and characterize the distribution and rate of occurrence of planets down to Earth size with no prior assumptions on their frequency, by subtracting from the population of actual Kepler candidates our simulated population of astrophysical false positives. We find that 16.5% {+-} 3.6% of main-sequence FGK stars have at least one planet between 0.8 and 1.25 R{sub Circled-Plus} with orbital periods up to 85 days. This result is a significant step toward the determination of eta-earth, the occurrence of Earth-like planets in the habitable zone of their parent stars. There is no significant dependence of the rates of planet

  18. Occurrence of False-Positive Most Probable Number Tests for Fecal Streptococci in Marine Waters1

    PubMed Central

    Buck, John D.

    1969-01-01

    By the use of the most probable number technique with azide dextrose and ethyl violet azide broths for enterococci, the common occurrence of false-positive tests was noted when marine and estuarine waters were sampled. Organisms isolated included a marine bacterium, gram-positive and gram-negative nonmarine bacteria, and yeasts. All cultures were capable of growth in azide-dextrose, ethyl violet-azide, and KF broths. Representative isolates grew in media containing 0.08% NaN3. The tentatively accepted most probable number method for fecal streptococci is thus of dubious value in assessment of sewage pollution levels in estuarine waters. All positive tubes must be examined microscopically for the presence of nonstreptococcal forms. PMID:4983956

  19. Reduction of false-positive recalls using a computerized mammographic image feature analysis scheme

    NASA Astrophysics Data System (ADS)

    Tan, Maxine; Pu, Jiantao; Zheng, Bin

    2014-08-01

    The high false-positive recall rate is one of the major dilemmas that significantly reduce the efficacy of screening mammography, which harms a large fraction of women and increases healthcare cost. This study aims to investigate the feasibility of helping reduce false-positive recalls by developing a new computer-aided diagnosis (CAD) scheme based on the analysis of global mammographic texture and density features computed from four-view images. Our database includes full-field digital mammography (FFDM) images acquired from 1052 recalled women (669 positive for cancer and 383 benign). Each case has four images: two craniocaudal (CC) and two mediolateral oblique (MLO) views. Our CAD scheme first computed global texture features related to the mammographic density distribution on the segmented breast regions of four images. Second, the computed features were given to two artificial neural network (ANN) classifiers that were separately trained and tested in a ten-fold cross-validation scheme on CC and MLO view images, respectively. Finally, two ANN classification scores were combined using a new adaptive scoring fusion method that automatically determined the optimal weights to assign to both views. CAD performance was tested using the area under a receiver operating characteristic curve (AUC). The AUC = 0.793  ±  0.026 was obtained for this four-view CAD scheme, which was significantly higher at the 5% significance level than the AUCs achieved when using only CC (p = 0.025) or MLO (p = 0.0004) view images, respectively. This study demonstrates that a quantitative assessment of global mammographic image texture and density features could provide useful and/or supplementary information to classify between malignant and benign cases among the recalled cases, which may eventually help reduce the false-positive recall rate in screening mammography.

  20. Positive hepatitis B virus core antibody in HIV infection--false positive or evidence of previous infection?

    PubMed

    Pallawela, S N S; Sonnex, C; Mabayoje, D; Bloch, E; Chaytor, S; Johnson, M A; Carne, C; Webster, D P

    2015-02-01

    Isolated HBV core antibody (anti-HBc) is defined as the presence of anti-HBc with a negative HBV surface antigen (HBsAg) and HBV surface antibody (anti-HBs <10 IU/l). In patients infected with HIV with isolated anti-HBc, the aim was to determine: The prevalence of isolated positive anti-HBc; The most effective method of identifying which patients have had previous Hepatitis B Virus (HBV) infection; The prevalence of false positive anti-HBc. HBV serology results were identified from 539 patients infected with HIV sampled between January 2010 and December 2012. In those with an isolated anti-HBc and negative anti-HBe, a second anti-HBc test was carried out using a different assay. Samples were also screened for HBV DNA. The anti-retroviral regimens at time of screening were documented. 101/539 had an isolated anti-HBc. Of these, 32 (32%) had a positive anti-HBe (including 1 equivocal) and 69(68%) were anti-HBe negative. Of those negative for anti-HBe, 32 were tested for both DNA and a second anti-HBc. Of these 26 (81%) were on cART at time of HBV testing, with 25 (78%) on ART with anti-HBV activity. The prevalence of isolated anti-HBc was 19%. Only 32% were also anti-HBe positive, whereas 97% of those anti-HBe negative were positive on a second anti-HBc assay suggesting lack of utility of anti-HBe in resolving serological quandaries. One subject (3%) had a false positive anti-HBc. There was no evidence of chronic HBV but 78% patients were on HBV-suppressive combination anti-retroviral therapy. PMID:25174739

  1. False Positivity of Non-Targeted Infections in Malaria Rapid Diagnostic Tests: The Case of Human African Trypanosomiasis

    PubMed Central

    Gillet, Philippe; Mumba Ngoyi, Dieudonné; Lukuka, Albert; Kande, Viktor; Atua, Benjamin; van Griensven, Johan; Muyembe, Jean-Jacques; Jacobs, Jan; Lejon, Veerle

    2013-01-01

    Background In endemic settings, diagnosis of malaria increasingly relies on the use of rapid diagnostic tests (RDTs). False positivity of such RDTs is poorly documented, although it is especially relevant in those infections that resemble malaria, such as human African trypanosomiasis (HAT). We therefore examined specificity of malaria RDT products among patients infected with Trypanosoma brucei gambiense. Methodology/Principal Findings Blood samples of 117 HAT patients and 117 matched non-HAT controls were prospectively collected in the Democratic Republic of the Congo. Reference malaria diagnosis was based on real-time PCR. Ten commonly used malaria RDT products were assessed including three two-band and seven three-band products, targeting HRP-2, Pf-pLDH and/or pan-pLDH antigens. Rheumatoid factor was determined in PCR negative subjects. Specificity of the 10 malaria RDT products varied between 79.5 and 100% in HAT-negative controls and between 11.3 and 98.8% in HAT patients. For seven RDT products, specificity was significantly lower in HAT patients compared to controls. False positive reactions in HAT were mainly observed for pan-pLDH test lines (specificities between 13.8 and 97.5%), but also occurred frequently for the HRP-2 test line (specificities between 67.9 and 98.8%). The Pf-pLDH test line was not affected by false-positive lines in HAT patients (specificities between 97.5 and 100%). False positivity was not associated to rheumatoid factor, detected in 7.6% of controls and 1.2% of HAT patients. Conclusions/Significance Specificity of some malaria RDT products in HAT was surprisingly low, and constitutes a risk for misdiagnosis of a fatal but treatable infection. Our results show the importance to assess RDT specificity in non-targeted infections when evaluating diagnostic tests. PMID:23638201

  2. False-positive reduction in CAD mass detection using a competitive classification strategy.

    PubMed

    Li, L; Zheng, Y; Zhang, L; Clark, R A

    2001-02-01

    High false-positive (FP) rate remains to be one of the major problems to be solved in CAD study because too many false-positively cued signals will potentially degrade the performance of detecting true-positive regions and increase the call-back rate in CAD environment. In this paper, we proposed a novel classification method for FP reduction, where the conventional "hard" decision classifier is cascaded with a "soft" decision classification with the objective to reduce false-positives in the cases with multiple FPs retained after the "hard" decision classification. The "soft" classification takes a competitive classification strategy in which only the "best" ones are selected from the pre-classified suspicious regions as the true mass in each case. A neural network structure is designed to implement the proposed competitive classification. Comparative studies of FP reduction on a database of 79 images by a "hard" decision classification and a combined "hard"-"soft" classification method demonstrated the efficiency of the proposed classification strategy. For example, for the high FP sub-database which has only 31.7% of total images but accounts for 63.5% of whole FPs generated in single "hard" classification, the FPs can be reduced for 56% (from 8.36 to 3.72 per image) by using the proposed method at the cost of 1% TP loss (from 69% to 68%) in whole database, while it can only be reduced for 27% (from 8.36 to 6.08 per image) by simply increasing the threshold of "hard" classifier with a cost of TP loss as high as 14% (from 69% to 55%). On the average in whole database, the FP reduction by hybrid "hard"-"soft" classification is 1.58 per image as compared to 1.11 by "hard" classification at the TP costs described above. Because the cases with high dense tissue are of higher risk of cancer incidence and false-negative detection in mammogram screening, and usually generate more FPs in CAD detection, the method proposed in this paper will be very helpful in improving

  3. Distinguishing True and False Positive Oxygen Signatures with Models and Observations

    NASA Astrophysics Data System (ADS)

    Schwieterman, Edward; Domagal-Goldman, Shawn; Meadows, Victoria; Luger, Rodrigo; Barnes, Rory; Wordsworth, Robin; Virtual Planetary Laboratory

    2015-01-01

    The spectral detection of oxygen (O2) or its photochemical bi-product ozone (O3) in a planetary atmosphere has been considered a robust signature of life because O2 is highly reactive and significant continuous abiotic sources were thought to be implausible. However, recent work has revealed the possibility that O2 or O3 may build up to spectrally detectable levels due to enhanced photolysis of O-bearing molecules by UV-active host stars (Domagal-Goldman et al. 2014, Tian et al. 2014) or photolysis of water and subsequent escape of hydrogen in thin (< 0.2 bar) atmospheres where the water is not cold trapped in the troposphere (Wordsworth et al. 2014). Additionally, there is the possibility that significant amounts of abiotic O2 could remain in post-runaway greenhouse atmospheres in the habitable zone of late type stars (Luger & Barnes 2014). Using photochemical and spectral models, we examine possible observing strategies that could discriminate between abiotic and biogenic oxygen scenarios. For example, false positives may be confirmed by the spectral detection of sibling molecules generated when large amounts of oxygen are photochemically produced (such as CO). False positives that result from H escape could be detected by measuring the mixing ratio of O2, which should be high (~1) when H escape causes O2 buildup. In contrast, true biosignatures could be confirmed by the simultaneous presence of a detectable reduced gas such as methane (CH4) which should not persist when O2 build up is caused by past H escape or by photochemical production of O2 in H-poor atmospheres. We use photochemical and spectral models to predict which combinations of planetary and stellar parameters will be most likely to produce conditions that would allow observational discrimination between true and false positives. We examine the spectral range, resolving power, and minimum integration times necessary to detect true and false positive indicators for a cross-section of model scenarios

  4. False positive I-131 MIBG due to dilated renal pelvis: a case report

    SciTech Connect

    Bahar, R.H.; Mahmoud, S.; Ibrahim, A.; al-Gazzar, A.H.

    1988-12-01

    A case of false positive I-131 MIBG imaging for detection of pheochromocytoma is presented. There was an area of increased tracer uptake in the left renal region that showed steadily reducing activity over a period of three days. This raised the suspicion of a dilated renal pelvis, which was later confirmed by Tc-99m DTPA imaging. It is advisable in cases of ambiguous I-131 MIBG imaging to use Tc-99m DTPA rather than Tc-99m DMSA for localizing the kidneys and renal pelvis.

  5. 68Ga-PSMA PET/CT False-Positive Tracer Uptake in Paget Disease.

    PubMed

    Sasikumar, Arun; Joy, Ajith; Nanabala, Raviteja; Pillai, M R A; T A, Hari

    2016-10-01

    65-year-old man with left-sided pelvic pain on evaluation was found to have features suggestive of either Paget disease or prostatic bone metastasis of the left hemipelvis based on Tc-MDP bone scan and MRI. Ga-PSMA PET/CT to assess the possibility of primary prostate cancer and if present to stage it helped to rule out prostate cancer because of absence of focal abnormal increased tracer uptake in the prostate gland. However, false-positive tracer uptake was noted in the left hemipelvis, which was subject to biopsy and histopathologically proven to be Paget disease involvement. PMID:27556797

  6. [Unexpected Diseases in Two Patients with False-Positive Dengue Immunoglobulin M Antibody Test Results].

    PubMed

    Matono, Takashi; Kutsuna, Satoshi; Kato, Yasuyuki; Takeshita, Nozomi; Hayakawa, Kayoko; Kanagawa, Shuzo; Ohmagari, Norio

    2016-03-01

    In 2014, an outbreak of 162 domestic dengue fever infections occurred in Tokyo, Japan; the first outbreak of its kind in 70 years. Nineteen of these cases were confirmed in our center. Advancements in diagnostic methods have enabled an earlier diagnosis of dengue fever; however, unfamiliarity with the clinical course and characteristics of diagnostic tests for dengue fever can lead to misdiagnosis. We herein describe 2 cases of Japanese patients with false-positive dengue immunoglobulin M antibody test results, who were finally diagnosed as having dermatomyositis and acute hepatitis A infection, respectively. PMID:27197439

  7. Finding False Positives Planet Candidates Due To Background Eclipsing Binaries in K2

    NASA Astrophysics Data System (ADS)

    Mullally, Fergal; Thompson, Susan E.; Coughlin, Jeffrey; DAVE Team

    2016-06-01

    We adapt the difference image centroid approach, used for finding background eclipsing binaries, to vet K2 planet candidates. Difference image centroids were used with great success to vet planet candidates in the original Kepler mission, where the source of a transit could be identified by subtracting images of out-of-transit cadences from in-transit cadences. To account for K2's roll pattern, we reconstruct out-of-transit images from cadences that are nearby in both time and spacecraft roll angle. We describe the method and discuss some K2 planet candidates which this method suggests are false positives.

  8. 68Ga-PSMA PET/CT False-Positive Tracer Uptake in Paget Disease.

    PubMed

    Sasikumar, Arun; Joy, Ajith; Nanabala, Raviteja; Pillai, M R A; T A, Hari

    2016-10-01

    65-year-old man with left-sided pelvic pain on evaluation was found to have features suggestive of either Paget disease or prostatic bone metastasis of the left hemipelvis based on Tc-MDP bone scan and MRI. Ga-PSMA PET/CT to assess the possibility of primary prostate cancer and if present to stage it helped to rule out prostate cancer because of absence of focal abnormal increased tracer uptake in the prostate gland. However, false-positive tracer uptake was noted in the left hemipelvis, which was subject to biopsy and histopathologically proven to be Paget disease involvement.

  9. PIPIDA scintigraphy for cholecystitis: false positives in alcoholism and total parenteral nutrition

    SciTech Connect

    Shuman, W.P.; Gibbs, P.; Rudd, T.G.; Mack, L.A.

    1982-01-01

    A review of gallbladder scintigraphy in patients with potentially compromised hepatobiliary function revealed two groups in whom cholecystitis might be mistakenly diagnosed. In 200 consecutive hospitalized patients studied with technetium-99m-PIPIDA for acute cholecystitis or cholestasis, there were 41 alcoholics and 17 patients on total parenteral nutrition. In 60% of the alcoholics and 92% of those on parenteral nutrition, absent or delayed visualization of the gallbladder occurred without physical or clinical evidence of cholecystitis. A cholecystagogue, sincalide, did not prevent the false-positive features which presumably are due to altered bile flow kinetics related to alcoholism and parenteral nutrition. Four patients on parenteral nutrition undergoing cholecystectomy for suspected cholecystitis had normal gallbladders filled with jellylike viscous thick bile. A positive (nonvisualized or delayed visualized) gallbladder PIPIDA scintigram in these two populations should not be interpreted as indicating a need for cholecystectomy.

  10. False positivity of FDG-PET/CT in a child with Hodgkin disease.

    PubMed

    Beker, Dildar Bahar; Berrak, Su Gulsun; Canpolat, Cengiz; Tugtepe, Halil; Ones, Tunc; Tecimer, Tulay

    2008-04-01

    Role of Positron Emission Tomography (PET) with F-18-2-fluoro-2-deoxy-D-glucose (FDG) in staging of Hodgkin disease is well established despite several controversies. We report a Stage III Hodgkin lymphoma patient with false positive FDG-PET/CT results. Seven-year-old male with Hodgkin lymphoma was in remission at end of chemotherapy. At third and fourth month of postchemotherapy follow-up, increased Gallium uptake and positive FDG-PET/CT in right lower quadrant of abdomen was observed. Open biopsy revealed lymphoid hyperplasia. He has been followed for 21 months without any evidence of disease. Despite its documented benefit, we believe that results of FDG-PET/CT should be interpreted with great caution in order to avoid unnecessary interventions. PMID:17417791

  11. False-positive results after environmental pinworm PCR testing due to Rhabditid nematodes in Corncob bedding.

    PubMed

    Leblanc, Mathias; Berry, Kristina; Graciano, Sandy; Becker, Brandon; Reuter, Jon D

    2014-11-01

    Modern rodent colonies are housed in individually ventilated cages to protect the animals from contamination with adventitious pathogens. Standard health monitoring through soiled-bedding sentinels does not always detect infections, especially in the context of low pathogen prevalence. Recently proposed alternatives include analyzing environmental samples from the cages or rack exhaust by PCR to improve the detection of rodent pathogens but optimal sampling strategies have not yet been established for different microorganisms. Although generally very sensitive and specific, these molecular assays are not foolproof and subject to false-positive and -negative results and should always be interpreted cautiously with an overall understanding of the intrinsic controls and all the variables that may affect the results. Here, we report a limited Aspiculuris tetraptera outbreak in a mouse barrier facility that was detected by fecal PCR in sentinels and confirmed by fecal flotation and direct cecal examination of both sentinels and colony animals. The outbreak led to a widespread survey of all facilities for pinworms by using environmental PCR from ventilated rack exhaust plenums. Environmental PCR suggested an unexpected widespread contamination of all ventilated racks holding nonautoclaved cages, but results could not be confirmed in sentinel or colony animals by fecal flotation, cecal and colonic examination, or cage PCR testing. After additional investigation, the unexpected environmental PCR results were confirmed as false-positive findings due to the nonspecificity of the assay, leading to the amplification of rhabditid nematodes, which are not infectious in rodents but which contaminated the corncob bedding.

  12. Robust correlation analyses: false positive and power validation using a new open source matlab toolbox.

    PubMed

    Pernet, Cyril R; Wilcox, Rand; Rousselet, Guillaume A

    2012-01-01

    Pearson's correlation measures the strength of the association between two variables. The technique is, however, restricted to linear associations and is overly sensitive to outliers. Indeed, a single outlier can result in a highly inaccurate summary of the data. Yet, it remains the most commonly used measure of association in psychology research. Here we describe a free Matlab((R)) based toolbox (http://sourceforge.net/projects/robustcorrtool/) that computes robust measures of association between two or more random variables: the percentage-bend correlation and skipped-correlations. After illustrating how to use the toolbox, we show that robust methods, where outliers are down weighted or removed and accounted for in significance testing, provide better estimates of the true association with accurate false positive control and without loss of power. The different correlation methods were tested with normal data and normal data contaminated with marginal or bivariate outliers. We report estimates of effect size, false positive rate and power, and advise on which technique to use depending on the data at hand.

  13. Avoiding false positives: zones of rarity, the threshold problem, and the DSM clinical significance criterion.

    PubMed

    Cooper, Rachel V

    2013-11-01

    False positives arise when people without disorders are diagnosed as having disorders. Various approaches for avoiding false positives have been suggested. This review critically assesses the roles of zones of rarity, the threshold problem (the problem of determining the boundary of disorder in cases that shade into normality), and the Diagnostic and Statistical Manual of Mental Disorders (DSM) criterion that requires that a disorder cause clinically significant impairment or distress (the harm criterion). The lack of zones of rarity in much of psychiatry gives rise to the threshold problem. The DSM harm criterion is frequently presented as offering a solution to the threshold problem. However, I argue that the harm criterion cannot offer a general solution to the threshold problem, as harm is not always correlated with the intensity and frequency of symptoms. Still, the harm criterion is essential to ensure that people who are merely different are not diagnosed as having a disorder. The threshold problem can be addressed by selecting symptom-based cut-off points to distinguish between disorder and normality. These cut-off points are frequently arbitrary in the sense that they often reflect no natural division between disorder and normal, but they may be more or less wisely chosen. Where possible, the thresholds should be set so that the advantages of diagnosis can be expected to outweigh the disadvantages.

  14. Vy-PER: eliminating false positive detection of virus integration events in next generation sequencing data.

    PubMed

    Forster, Michael; Szymczak, Silke; Ellinghaus, David; Hemmrich, Georg; Rühlemann, Malte; Kraemer, Lars; Mucha, Sören; Wienbrandt, Lars; Stanulla, Martin; Franke, Andre

    2015-01-01

    Several pathogenic viruses such as hepatitis B and human immunodeficiency viruses may integrate into the host genome. These virus/host integrations are detectable using paired-end next generation sequencing. However, the low number of expected true virus integrations may be difficult to distinguish from the noise of many false positive candidates. Here, we propose a novel filtering approach that increases specificity without compromising sensitivity for virus/host chimera detection. Our detection pipeline termed Vy-PER (Virus integration detection bY Paired End Reads) outperforms existing similar tools in speed and accuracy. We analysed whole genome data from childhood acute lymphoblastic leukemia (ALL), which is characterised by genomic rearrangements and usually associated with radiation exposure. This analysis was motivated by the recently reported virus integrations at genomic rearrangement sites and association with chromosomal instability in liver cancer. However, as expected, our analysis of 20 tumour and matched germline genomes from ALL patients finds no significant evidence for integrations by known viruses. Nevertheless, our method eliminates 12,800 false positives per genome (80× coverage) and only our method detects singleton human-phiX174-chimeras caused by optical errors of the Illumina HiSeq platform. This high accuracy is useful for detecting low virus integration levels as well as non-integrated viruses. PMID:26166306

  15. A high false positive rate for Kepler planetary candidates of giant stars using asterodensity profiling

    SciTech Connect

    Sliski, David H.; Kipping, David M.

    2014-06-20

    Asterodensity profiling (AP) is a relatively new technique for studying transit light curves. By comparing the mean stellar density derived from the transit light curve to that found through an independent method, AP provides information on several useful properties such as orbital eccentricity and blended light. We present an AP survey of 41 Kepler Objects of Interest (KOIs), with a single transiting candidate, for which the target star's mean stellar density has been measured using asteroseismology. The ensemble distribution of the AP measurements for the 31 dwarf stars in our sample shows excellent agreement with the spread expected if the KOIs were genuine and have realistic eccentricities. In contrast, the same test for the 10 giants in our sample reveals significant incompatibility at >4σ confidence. While extreme eccentricities could be invoked, this hypothesis requires four of the KOIs to contact their host star at periastron passage, including the recently claimed confirmation of Kepler-91b. After carefully examining several hypotheses, we conclude that the most plausible explanation is that the transiting objects orbit a different star to that measured with asteroseismology—cases we define as false-positives. Based on the AP distribution, we estimate a false-positive rate (FPR) for Kepler's giant stars with a single transiting object of FPR ≅ 70% ± 30%.

  16. False-Positive Results after Environmental Pinworm PCR Testing due to Rhabditid Nematodes in Corncob Bedding

    PubMed Central

    Leblanc, Mathias; Berry, Kristina; Graciano, Sandy; Becker, Brandon; Reuter, Jon D

    2014-01-01

    Modern rodent colonies are housed in individually ventilated cages to protect the animals from contamination with adventitious pathogens. Standard health monitoring through soiled-bedding sentinels does not always detect infections, especially in the context of low pathogen prevalence. Recently proposed alternatives include analyzing environmental samples from the cages or rack exhaust by PCR to improve the detection of rodent pathogens but optimal sampling strategies have not yet been established for different microorganisms. Although generally very sensitive and specific, these molecular assays are not foolproof and subject to false-positive and –negative results and should always be interpreted cautiously with an overall understanding of the intrinsic controls and all the variables that may affect the results. Here, we report a limited Aspiculuris tetraptera outbreak in a mouse barrier facility that was detected by fecal PCR in sentinels and confirmed by fecal flotation and direct cecal examination of both sentinels and colony animals. The outbreak led to a widespread survey of all facilities for pinworms by using environmental PCR from ventilated rack exhaust plenums. Environmental PCR suggested an unexpected widespread contamination of all ventilated racks holding nonautoclaved cages, but results could not be confirmed in sentinel or colony animals by fecal flotation, cecal and colonic examination, or cage PCR testing. After additional investigation, the unexpected environmental PCR results were confirmed as false-positive findings due to the nonspecificity of the assay, leading to the amplification of rhabditid nematodes, which are not infectious in rodents but which contaminated the corncob bedding. PMID:25650980

  17. Vy-PER: eliminating false positive detection of virus integration events in next generation sequencing data.

    PubMed

    Forster, Michael; Szymczak, Silke; Ellinghaus, David; Hemmrich, Georg; Rühlemann, Malte; Kraemer, Lars; Mucha, Sören; Wienbrandt, Lars; Stanulla, Martin; Franke, Andre

    2015-07-13

    Several pathogenic viruses such as hepatitis B and human immunodeficiency viruses may integrate into the host genome. These virus/host integrations are detectable using paired-end next generation sequencing. However, the low number of expected true virus integrations may be difficult to distinguish from the noise of many false positive candidates. Here, we propose a novel filtering approach that increases specificity without compromising sensitivity for virus/host chimera detection. Our detection pipeline termed Vy-PER (Virus integration detection bY Paired End Reads) outperforms existing similar tools in speed and accuracy. We analysed whole genome data from childhood acute lymphoblastic leukemia (ALL), which is characterised by genomic rearrangements and usually associated with radiation exposure. This analysis was motivated by the recently reported virus integrations at genomic rearrangement sites and association with chromosomal instability in liver cancer. However, as expected, our analysis of 20 tumour and matched germline genomes from ALL patients finds no significant evidence for integrations by known viruses. Nevertheless, our method eliminates 12,800 false positives per genome (80× coverage) and only our method detects singleton human-phiX174-chimeras caused by optical errors of the Illumina HiSeq platform. This high accuracy is useful for detecting low virus integration levels as well as non-integrated viruses.

  18. Vy-PER: eliminating false positive detection of virus integration events in next generation sequencing data

    PubMed Central

    Forster, Michael; Szymczak, Silke; Ellinghaus, David; Hemmrich, Georg; Rühlemann, Malte; Kraemer, Lars; Mucha, Sören; Wienbrandt, Lars; Stanulla, Martin; Franke, Andre

    2015-01-01

    Several pathogenic viruses such as hepatitis B and human immunodeficiency viruses may integrate into the host genome. These virus/host integrations are detectable using paired-end next generation sequencing. However, the low number of expected true virus integrations may be difficult to distinguish from the noise of many false positive candidates. Here, we propose a novel filtering approach that increases specificity without compromising sensitivity for virus/host chimera detection. Our detection pipeline termed Vy-PER (Virus integration detection bY Paired End Reads) outperforms existing similar tools in speed and accuracy. We analysed whole genome data from childhood acute lymphoblastic leukemia (ALL), which is characterised by genomic rearrangements and usually associated with radiation exposure. This analysis was motivated by the recently reported virus integrations at genomic rearrangement sites and association with chromosomal instability in liver cancer. However, as expected, our analysis of 20 tumour and matched germline genomes from ALL patients finds no significant evidence for integrations by known viruses. Nevertheless, our method eliminates 12,800 false positives per genome (80× coverage) and only our method detects singleton human-phiX174-chimeras caused by optical errors of the Illumina HiSeq platform. This high accuracy is useful for detecting low virus integration levels as well as non-integrated viruses. PMID:26166306

  19. Reducing false positive findings in statistical analysis of pharmacogenomic biomarker studies using high-throughput technologies.

    PubMed

    Matsui, Shigeyuki

    2006-05-01

    The promise of pharmacogenomics lies in the potential to establish a personalized drug therapy with the intent of maximizing effectiveness and minimizing risk, through development of pharmacogenomics biomarkers. However, currently, most pharmacogenomic measurements are not considered valid biomarkers with clear clinical significance, thus this field is in early developmental stages. Recently, the development of comprehensive, high-throughput technologies such as gene expression microarrays has provided powerful new tools for these stages. This technological transformation is, at the same time, generating an increasing demand for statistical analysis of large and complex multivariate datasets from high-throughput assays. This article provides a review of the key features to be observed in statistical analyses of large amounts of data from pharmacogenomic biomarker studies with high-throughput assays. The problem of false positive can be very serious in such studies. The evaluation of stability and reproducibility of the results of statistical analysis are claimed to reduce chance that false positive findings are subject to further investigation in subsequent studies.

  20. Fenofibric Acid Can Cause False-Positive Urine Methylenedioxymethamphetamine Immunoassay Results.

    PubMed

    Quesada, Loreto; Gomila, Isabel; Fe, Antonia; Servera, Miguel A; Yates, Christopher; Morell-Garcia, Daniel; Castanyer, Bartomeu; Barceló, Bernardino

    2015-01-01

    We present a false-positive result of ecstasy (3,4-methylenedioxy-NN-methylamphetamine) screening due to the therapeutic use of fenofibrate, an antihyperlipidemic drug. Our hypothesis was that the main metabolite of fenofibrate, fenofibric acid, was responsible for this cross-reactivity on a DRI(®) Ecstasy Assay, using a cut-off of 500 ng/mL. We estimated that the addition of 225 µg/mL pure fenofibric acid to blank urine would be sufficient to result in a positive DRI(®) Ecstasy Assay. The results obtained on the urine samples analyses of the patient show that the DRI(®) Ecstasy Assay resulted negative 2 days after discontinuing fenofibrate treatment, when the urine fenofibric acid concentration corrected by creatinine and determinated by gas chromatography-mass spectrometry was 20.3 µg/mg creatinine. The cross-reactivity data for fenofibric acid would seem to indicate that there was insufficient concentration of measured compound to account for the positive immunochemical results for ecstasy. This apparent discrepancy can be explained in several ways, one of them is that the β-glucuronidase-resistent fenofibric acid isomers are responsible. This process could explain the low recovery of free fenofibric acid when we use the developed method for its quantification in urine samples. Positive results on immunoassay screening must be considered presumptive until confirmation with another method based on a different principle, preferably gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry.

  1. Blue-white screening liquid can eliminate false positives in blue-white colony screening.

    PubMed

    Zhang, Y S

    2016-06-10

    Although blue-white screening based on α-complementation has been widely used in the screening of genetically modified bacteria, only a single blue-white screening is typically not enough to eliminate false positives. Sometimes, a secondary blue-white screening for the target colonies is required. In this study, two methods were used to investigate the feasibility of secondary blue-white screening for target colonies on lysogeny broth (LB)-ampicillin agar plates. The first method consisted of covering the target colonies grown on LB-ampicillin plate medium with a sterilized filter paper soaked in a solution of 60 μL 20 mg/mL X-gal and 8 μL 20% IPTG. The second method was that blue and white colonies were randomly selected from the blue-white screening plate medium and then re-streaked onto the blue-white screening medium. The colonies were then treated by two methods and incubated at 37°C for 12 h. The results showed that some of the white colonies treated by the two methods showed results similar to the colonies grown on the blue-white screening medium. These results indicate that the target colonies grown on blue-white screening medium can still be used to carry out a secondary blue-white screening. Thus, a blue-white screening liquid was successfully developed. Using the blue-white screening liquid, false positives can be eliminated directly based on the color of the target colonies. This will greatly improve the screening efficiency of positive clones and has important practical implications.

  2. Blue-white screening liquid can eliminate false positives in blue-white colony screening.

    PubMed

    Zhang, Y S

    2016-01-01

    Although blue-white screening based on α-complementation has been widely used in the screening of genetically modified bacteria, only a single blue-white screening is typically not enough to eliminate false positives. Sometimes, a secondary blue-white screening for the target colonies is required. In this study, two methods were used to investigate the feasibility of secondary blue-white screening for target colonies on lysogeny broth (LB)-ampicillin agar plates. The first method consisted of covering the target colonies grown on LB-ampicillin plate medium with a sterilized filter paper soaked in a solution of 60 μL 20 mg/mL X-gal and 8 μL 20% IPTG. The second method was that blue and white colonies were randomly selected from the blue-white screening plate medium and then re-streaked onto the blue-white screening medium. The colonies were then treated by two methods and incubated at 37°C for 12 h. The results showed that some of the white colonies treated by the two methods showed results similar to the colonies grown on the blue-white screening medium. These results indicate that the target colonies grown on blue-white screening medium can still be used to carry out a secondary blue-white screening. Thus, a blue-white screening liquid was successfully developed. Using the blue-white screening liquid, false positives can be eliminated directly based on the color of the target colonies. This will greatly improve the screening efficiency of positive clones and has important practical implications. PMID:27323169

  3. Implications for the False-positive Rate in Kepler Planet Systems from Transit Duration Ratios

    NASA Astrophysics Data System (ADS)

    Morehead, Robert C.; Ford, Eric B.

    2015-01-01

    Confirming transiting exoplanet candidates through traditional follow-up methods is challenging, especially for faint host stars. Most of Kepler's validated planets relied on statistical methods to separate true planets from false-positives. Multiple transiting planet systems (MTPS) have been previously shown to have low false-positive rates and over 851 planets in MTPSs have been statistically validated so far (Lissauer et al. 2014; Rowe et al. 2014). We show that the period-normalized transit duration ratio (ξ) offers additional information that can be used to establish the planetary nature of these systems. We briefly discuss the observed distribution of ξ for the Q1-Q16 Kepler Candidate Search. We also utilize ξ to develop a Bayesian statistical framework combined with Monte Carlo methods to determine which pairs of planet candidates in a MTPS are consistent with the planet hypothesis for a sample of 676 MTPSs that include both candidate and confirmed planets. This analysis proves to be efficient and advantageous in that it only requires catalog-level bulk candidate properties and galactic population modeling to compute the probabilities of a myriad of stellar blend scenarios, without needing additional observational follow-up. Our results agree with the previous results of a low false-positive rate in the Kepler MTPSs. Out of our sample of 1,358 pairs of candidates, we find that about 100 pairs have a probability greater than 0.99 of being a MTPS associated with the target star, over 800 pairs have a probability greater than 0.99 of being a MTPS associated with the target star or another star blended in the photometric aperture. Further more, we find that well over a 1,000 pairs have a probability greater than 0.99 to be planetary in nature, either orbiting the same star or separately orbiting two different stars in the aperture. This implies, independently of any other estimates, that most of the MTPSs detected by Kepler are very likely to be planetary in

  4. False-positive buprenorphine by CEDIA in patients prescribed amisulpride or sulpiride.

    PubMed

    Birch, M A; Couchman, L; Pietromartire, S; Karna, T; Paton, C; McAllister, R; Marsh, A; Flanagan, R J

    2013-05-01

    Buprenorphine is a potent partial opioid agonist that is analyzed in urine to (i) monitor adherence to maintenance or detoxification therapy and (ii) detect illicit use. Buprenorphine analysis is commonly conducted on urine by immunoassay, but is subject to cross-reactivity from other drugs/drug metabolites, including morphine, codeine and dihydrocodeine. This study reports false-positive buprenorphine analysis [Thermo Fisher Scientific cloned enzyme donor immunoassay (CEDIA)] in patients who denied unauthorized buprenorphine use prior to sampling, but who had been prescribed amisulpride. In two cases, confirmatory analysis by liquid chromatography-tandem mass spectrometry was negative (<0.5 µg/L) for buprenorphine and metabolites and positive for amisulpride. Although the cross-reactivity of amisulpride and sulpiride in the CEDIA buprenorphine assay is low (estimated at 0.003 and 0.002%, respectively), it remains a significant consideration given the likely high concentrations of these compounds in urine relative to the low cutoff of the buprenorphine assay. Neither amisulpride nor sulpiride was listed as potential sources of interference on the CEDIA data sheet when this work was performed. These findings highlight the importance of confirming immunoassay-positive buprenorphine results using a more selective analytical technique.

  5. Reduction of false positives on the rectal tube in computer-aided detection for CT colonography

    SciTech Connect

    Iordanescu, Gheorghe; Summers, Ronald M.

    2004-10-01

    Purpose: To eliminate false-positive (FP) polyp detections on the rectal tube (RT) in CT colonography (CTC) computer-aided detection (CAD). Methods: We use a three-stage approach to detect the RT: detect the RT shaft, track the tube to the tip and label all the voxels that belong to the RT. We applied our RT detection algorithm on a CTC dataset consisting of 80 datasets (40 patients scanned in both prone and supine positions). Two different types of RTs were present, characterized by differences in shaft/bulb diameters, wall intensities, and shape of tip. Results: The algorithm detected 90% of RT shafts and completely tracked 72% of them. We labeled all the voxels belonging to the completely tracked RTs (72%) and in 11 out of 80 (14%) cases the RT voxels were partially labeled. We obtained a 9.2% reduction of the FPs in the initial polyp candidates' population, and a 7.9% reduction of the FPs generated by our CAD system. None of the true-positive detections were mislabeled. Conclusions: The algorithm detects the RTs with good accuracy, is robust with respect to the two different types of RT used in our study, and is effective at reducing the number of RT FPs reported by our CAD system.

  6. Pulmonary sequestration: a (131)I whole body scintigraphy false-positive result.

    PubMed

    Spinapolice, Elena Giulia; Chytiris, S; Fuccio, C; Leporati, P; Volpato, G; Villani, L; Trifirò, G; Chiovato, L

    2014-08-01

    A 35-year-old woman affected by a well-differentiated papillary thyroid carcinoma was referred to our hospital to perform a (131)Iodine ((131)I) whole body scintigraphy for restaging purpose. The patient had been previously treated with total thyroidectomy and three subsequent doses of (131)I for the ablation of a remnant jugular tissue and a suspected metastatic focus at the superior left hemi-thorax. In spite of the previous treatments with (131)I, planar and tomographic images showed the persistence of an area of increased uptake at the superior left hemi-thorax. This finding prompted the surgical resection of the lesion. Histological examination of the surgical specimen showed the presence of a pulmonary tissue consistent with pulmonary sequestration. Even though rare, pulmonary sequestration should be included in the potential causes of false-positive results of radioiodine scans.

  7. From docking false-positive to active anti-HIV agent.

    PubMed

    Barreiro, Gabriela; Kim, Joseph T; Guimarães, Cristiano R W; Bailey, Christopher M; Domaoal, Robert A; Wang, Ligong; Anderson, Karen S; Jorgensen, William L

    2007-11-01

    Virtual screening of the Maybridge library of ca. 70 000 compounds was performed using a similarity filter, docking, and molecular mechanics-generalized Born/surface area postprocessing to seek potential non-nucleoside inhibitors of human immunodeficiency virus-1 (HIV-1) reverse transcriptase (NNRTIs). Although known NNRTIs were retrieved well, purchase and assaying of representative, top-scoring compounds from the library failed to yield any active anti-HIV agents. However, the highest-ranked library compound, oxadiazole 1, was pursued as a potential "near-miss" with the BOMB program to seek constructive modifications. Subsequent synthesis and assaying of several polychloro-analogs did yield anti-HIV agents with EC50 values as low as 310 nM. The study demonstrates that it is possible to learn from a formally unsuccessful virtual-screening exercise and, with the aid of computational analyses, to efficiently evolve a false positive into a true active. PMID:17918923

  8. Quantification of false positive reduction in nucleic acid purification on hemorrhagic fever DNA.

    SciTech Connect

    James, Conrad D.; Pohl, Kenneth Roy; Derzon, Mark Steven; McClain, Jaime; Achyuthan, Komandoor

    2006-11-01

    Columbia University has developed a sensitive highly multiplexed system for genetic identification of nucleic acid targets. The primary obstacle to implementing this technology is the high rate of false positives due to high levels of unbound reporters that remain within the system after hybridization. The ability to distinguish between free reporters and reporters bound to targets limits the use of this technology. We previously demonstrated a new electrokinetic method for binary separation of kb pair long DNA molecules and oligonucleotides. The purpose of this project 99864 is to take these previous demonstrations and further develop the technique and hardware for field use. Specifically, our objective was to implement separation in a heterogeneous sample (containing target DNA and background oligo), to perform the separation in a flow-based device, and to develop all of the components necessary for field testing a breadboard prototype system.

  9. False positive reduction for pulmonary nodule detection using two-dimensional principal component analysis

    NASA Astrophysics Data System (ADS)

    Choi, Wook-Jin; Choi, Tae-Sun

    2009-08-01

    Pulmonary nodule detection is a binary classification problem. The main objective is to classify nodule from the lung computed tomography (CT) images. The intra class variability is mainly due to the grey-level variance, texture differences and shape. The purpose of this study is to develop a novel nodule detection method which is based on Two-dimensional Principal Component Analysis (2DPCA). We extract the futures using 2DPCA from nodule candidate images. Nodule candidates are classified using threshold. The proposed method reduces False Positive (FP) rate. We tested the proposed algorithm by using Lung Imaging Database Consortium (LIDC) database of National Cancer Institute (NCI). The experimental results demonstrate the effectiveness and efficiency of the proposed method. The proposed method achieved 85.11% detection rate with 1.13 FPs per scan.

  10. False-positive pH aspirates after nasogastric tube insertion in head and neck tumour.

    PubMed

    Sellers, Claudia Kate

    2012-08-27

    Nasogastric (NG) feeding tubes are commonly inserted to supplement enteral nutrition in certain patient groups, including those with head and neck cancers where swallowing may be compromised. An NHS National Patient Safety Alert was released in 2011 detailing ongoing cases of significant morbidity and mortality attached to the incorrect placement of NG feeding tubes in hospital inpatients. Since 2005, there were 21 deaths and 79 cases of harm nationally due to feeding into the lung through misplaced tubes. pH testing remains the first-line method of placement confirmation, with chest x-ray used when no aspirate is gained or where pH testing fails to confirm suitable acidity. We present a case report describing false-positive NG tube placement confirmation tests in a patient with head and neck cancer, who was administered feed into lung parenchyma with significant morbidity. We discuss the case for specific NG tube placement protocols in head and neck cancer patients.

  11. Correct assessment of new compounds using in vivo screening models can reduce false positives.

    PubMed

    Bueters, Tjerk J H; Hoogstraate, Janet; Visser, Sandra A G

    2009-01-01

    During early drug discovery the initial in vivo efficacy testing is often performed in rodent models optimized to screen and select lead compounds rapidly, before progressing them to in vivo models that reflect the human form of the disease more closely. The way such models are frequently run can risk overestimating the efficacy of new compounds when using pre- and co-administration, as shown in three examples from different central nervous system research areas. This is undesirable for reasons ranging from good decision-making, cost efficiency and time management to the ethics of animal use. Abandoning the use of pre-treatment, monitoring crucial physiological parameters in (satellite) animals and systematically applying simple pharmacokinetic-pharmacodynamic analysis could reduce the number of false positive results.

  12. Eliminating false positive C4 sugar tests on New Zealand Manuka honey.

    PubMed

    Rogers, Karyne M; Somerton, Kerry; Rogers, Pamela; Cox, Julie

    2010-08-30

    Carbon isotope analyses (delta(13)C) of some New Zealand Manuka honeys show that they often fail the internationally recognised Association of Official Analytical Chemists sugar test (AOAC method 998.12) which detects added C(4) sugar, although these honeys are from unadulterated sources. Failure of these high value products is detrimental to the New Zealand honey industry, not only in lost export revenue, but also in brand and market reputation damage. The standard AOAC test compares the carbon isotope value of the whole honey and corresponding protein isolated from the same honey. Differences between whole honey and protein delta(13)C values should not be greater than +1.0 per thousand, as it indicates the possibility of adulteration with syrups or sugars from C(4) plants such as high fructose corn syrup or cane sugar.We have determined that during the standard AOAC method, pollen and other insoluble components are isolated with the flocculated protein. These non-protein components have isotope values which are considerably different from those of the pure protein, and can shift the apparent delta(13)C value of protein further away from the delta(13)C value of the whole honey, giving a false positive result for added C(4) sugar. To eliminate a false positive C(4) sugar test for Manuka honey, prior removal of pollen and other insoluble material from the honey is necessary to ensure that only the pure protein is isolated. This will enable a true comparison between whole honey and protein delta(13)C isotopes. Furthermore, we strongly suggest this modification to the AOAC method be universally adopted for all honey C(4) sugar tests.

  13. False-positive rates associated with the use of multiple performance and symptom validity tests.

    PubMed

    Larrabee, Glenn J

    2014-06-01

    Performance validity test (PVT) error rates using Monte Carlo simulation reported by Berthelson and colleagues (in False positive diagnosis of malingering due to the use of multiple effort tests. Brain Injury, 27, 909-916, 2013) were compared with PVT and symptom validity test (SVT) failure rates in two nonmalingering clinical samples. At a per-test false-positive rate of 10%, Monte Carlo simulation overestimated error rates for: (i) failure of ≥2 out of 5 PVTs/SVT for Larrabee (in Detection of malingering using atypical performance patterns on standard neuropsychological tests. The Clinical Neuropsychologist, 17, 410-425, 2003) and ACS (Pearson, Advanced clinical solutions for use with WAIS-IV and WMS-IV. San Antonio: Pearson Education, 2009) and (ii) failure of ≥2 out of 7 PVTs/SVT for Larrabee (Detection of malingering using atypical performance patterns on standard neuropsychological tests. The Clinical Neuropsychologist, 17, 410-425, 2003; Malingering scales for the Continuous Recognition Memory Test and Continuous Visual Memory Test. The Clinical Neuropsychologist, 23, 167-180, 2009 combined). Monte Carlo overestimation is likely because PVT performances are atypical in pattern or degree for what occurs in actual neurologic, psychiatric, or developmental disorders. Consequently, PVT scores form skewed distributions with performance at ceiling and restricted range, rather than forming a standard normal distribution with mean of 0 and standard deviation of 1.0. These results support the practice of using ≥2 PVT/SVT failures as representing probable invalid clinical presentation. PMID:24769887

  14. False-positive Extra-Mammary Findings in Breast MRI: Another Cause for Concern.

    PubMed

    Padia, Shilpa A; Freyvogel, Mary; Dietz, Jill; Valente, Stephanie; O'Rourke, Colin; Grobmyer, Stephen R

    2016-01-01

    Breast magnetic resonance imaging (MRI) has been repeatedly shown to have a high false-positive rate for additional findings in the breast resulting in additional breast imaging and biopsies. We hypothesize that breast MRI is also associated with a high rate of false-positive findings outside of the breast requiring additional evaluation, interventions, and delays in treatment. We performed a retrospective review of all breast MRIs performed on breast cancer patients in 2010 at a single institution. MRI reports were analyzed for extra-mammary findings. The timing and yield of the additional procedures was also analyzed. Three hundred and twenty-seven breast cancer patients (average age = 53.53 ± 11.08 years) had a breast MRI. Incidental, extra-mammary findings were reported in 35/327 patients (10.7%) with a total of 38 incidental findings. The extra-mammary findings were located in the liver (n = 21, 60.0%), thoracic cavity (n = 12, 34.3%), kidneys (n = 1, 2.9%), musculoskeletal system (n = 3, 8.6%), and neck (n = 1, 2.9%). Eighteen of the 35 patients (51.4%) received additional radiographic imaging, 3 (8.6%) received additional laboratory testing, 2 (5.7%) received additional physician referrals and 2 (5.7%) received a biopsy of the finding. The average time to additional procedures in these patients was 14.5 days. None of the incidental, extra-mammary findings were associated with breast cancer or other malignancy. Breast MRI was associated with a high rate (10.7%) of extra-mammary findings, which led to costly additional imaging studies, referrals, and tests. These findings were not associated with breast cancer or other malignancies. Extra-mammary findings highlight an unrecognized adverse consequence of breast MRI.

  15. Eliminating false positive C4 sugar tests on New Zealand Manuka honey.

    PubMed

    Rogers, Karyne M; Somerton, Kerry; Rogers, Pamela; Cox, Julie

    2010-08-30

    Carbon isotope analyses (delta(13)C) of some New Zealand Manuka honeys show that they often fail the internationally recognised Association of Official Analytical Chemists sugar test (AOAC method 998.12) which detects added C(4) sugar, although these honeys are from unadulterated sources. Failure of these high value products is detrimental to the New Zealand honey industry, not only in lost export revenue, but also in brand and market reputation damage. The standard AOAC test compares the carbon isotope value of the whole honey and corresponding protein isolated from the same honey. Differences between whole honey and protein delta(13)C values should not be greater than +1.0 per thousand, as it indicates the possibility of adulteration with syrups or sugars from C(4) plants such as high fructose corn syrup or cane sugar.We have determined that during the standard AOAC method, pollen and other insoluble components are isolated with the flocculated protein. These non-protein components have isotope values which are considerably different from those of the pure protein, and can shift the apparent delta(13)C value of protein further away from the delta(13)C value of the whole honey, giving a false positive result for added C(4) sugar. To eliminate a false positive C(4) sugar test for Manuka honey, prior removal of pollen and other insoluble material from the honey is necessary to ensure that only the pure protein is isolated. This will enable a true comparison between whole honey and protein delta(13)C isotopes. Furthermore, we strongly suggest this modification to the AOAC method be universally adopted for all honey C(4) sugar tests. PMID:20635333

  16. Gene expression profiling in primary mouse hepatocytes discriminates true from false-positive genotoxic compounds.

    PubMed

    Mathijs, K; Brauers, K J J; Jennen, D G J; Lizarraga, D; Kleinjans, J C S; van Delft, J H M

    2010-11-01

    Well-established in vitro methods for testing the genotoxic potency of chemicals--such as the Ames/Salmonella test, the mouse lymphoma assay, the micronucleus test and the chromosomal aberration test--show a high false-positive rate for predicting in vivo genotoxicity and carcinogenicity. Thus, there is a need for more reliable in vitro assays. We investigated whether gene expression profiling in metabolically competent primary mouse hepatocytes is capable of discriminating true genotoxic (GTX) compounds from false-positive genotoxic (FP-GTX) compounds. Sandwich-cultured primary hepatocytes from male C57Bl6 mice were treated for 24 and 48 h with five true GTX and five FP-GTX compounds. Whole genome gene expression modifications were analysed by means of Affymetrix mouse genome 430 2.0 microarrays. Filtered genes were used for hierarchical clustering and class prediction methods. Classifiers were generated by prediction analysis of microarray using a leave-one-compound-out method and selecting the genes that were common to the 10 training sets. For the training compounds, all but one were correctly classified. Validation of the classification model with five new compounds resulted in a 100% correct classification at 24 h and 80% at 48 h. The generated classifiers were mostly involved in metabolic and biosynthetic processes, immune responses and apoptosis. Applying genes whose expression change correlates with γH2AX foci, a measure for DNA damage, did not improve the classification. The present study shows that gene expression profiling in primary mouse hepatocytes is capable of discriminating between true GTX and FP-GTX compounds.

  17. Pre-spectroscopic False-positive Elimination of Kepler Planet Candidates

    NASA Astrophysics Data System (ADS)

    Batalha, Natalie M.; Rowe, Jason F.; Gilliland, Ronald L.; Jenkins, Jon J.; Caldwell, Douglas; Borucki, William J.; Koch, David G.; Lissauer, Jack J.; Dunham, Edward W.; Gautier, Thomas N.; Howell, Steve B.; Latham, David W.; Marcy, Geoff W.; Prsa, Andrej

    2010-04-01

    Ten days of commissioning data (Quarter 0) and 33 days of science data (Quarter 1) yield instrumental flux time series of ~150,000 stars that were combed for transit events, termed threshold crossing events(TCE), each having a total detection statistic above 7.1σ. TCE light curves are modeled as star+planet systems. Those returning a companion radius smaller than 2RJ are assigned a Kepler Object of Interest (KOI) number. The raw flux, pixel flux, and flux-weighted centroids of every KOI are scrutinized to assess the likelihood of being an astrophysical false positive versus the likelihood of being a planetary companion. This vetting using Kepler data is referred to as data validation (DV). Herein, we describe the DV metrics and graphics used to identify viable planet candidates amongst the KOIs. Light curve modeling tests for (1) the difference in depth of the odd- versus even-numbered transits, (2) evidence of ellipsoidal variations, and (3) evidence of a secondary eclipse event at phase = 0.5. Flux-weighted centroids are used to test for signals correlated with transit events with a magnitude and direction indicative of a background eclipsing binary. Centroid time series are complimented by analysis of images taken in-transit versus out-of-transit, the difference often revealing the pixel contributing the most to the flux change during transit. Examples are shown to illustrate each test. Candidates passing DV are submitted to ground-based observers for further false-positive elimination or confirmation/characterization.

  18. PRE-SPECTROSCOPIC FALSE-POSITIVE ELIMINATION OF KEPLER PLANET CANDIDATES

    SciTech Connect

    Batalha, Natalie M.; Rowe, Jason F.; Borucki, William J.; Koch, David G.; Lissauer, Jack J.; Gilliland, Ronald L.; Jenkins, Jon J.; Caldwell, Douglas; Dunham, Edward W.; Gautier, Thomas N.; Howell, Steve B.; Latham, David W.; Marcy, Geoff W.; Prsa, Andrej

    2010-04-20

    Ten days of commissioning data (Quarter 0) and 33 days of science data (Quarter 1) yield instrumental flux time series of {approx}150,000 stars that were combed for transit events, termed threshold crossing events(TCE), each having a total detection statistic above 7.1{sigma}. TCE light curves are modeled as star+planet systems. Those returning a companion radius smaller than 2R{sub J} are assigned a Kepler Object of Interest (KOI) number. The raw flux, pixel flux, and flux-weighted centroids of every KOI are scrutinized to assess the likelihood of being an astrophysical false positive versus the likelihood of being a planetary companion. This vetting using Kepler data is referred to as data validation (DV). Herein, we describe the DV metrics and graphics used to identify viable planet candidates amongst the KOIs. Light curve modeling tests for (1) the difference in depth of the odd- versus even-numbered transits, (2) evidence of ellipsoidal variations, and (3) evidence of a secondary eclipse event at phase = 0.5. Flux-weighted centroids are used to test for signals correlated with transit events with a magnitude and direction indicative of a background eclipsing binary. Centroid time series are complimented by analysis of images taken in-transit versus out-of-transit, the difference often revealing the pixel contributing the most to the flux change during transit. Examples are shown to illustrate each test. Candidates passing DV are submitted to ground-based observers for further false-positive elimination or confirmation/characterization.

  19. A FALSE POSITIVE FOR OCEAN GLINT ON EXOPLANETS: THE LATITUDE-ALBEDO EFFECT

    SciTech Connect

    Cowan, Nicolas B.; Abbot, Dorian S.; Voigt, Aiko

    2012-06-10

    Identifying liquid water on the surface of planets is a high priority, as this traditionally defines habitability. One proposed signature of oceans is specular reflection ('glint'), which increases the apparent albedo of a planet at crescent phases. We post-process a global climate model of an Earth-like planet to simulate reflected light curves. Significantly, we obtain glint-like phase variations even though we do not include specular reflection in our model. This false positive is the product of two generic properties: (1) for modest obliquities, a planet's poles receive less orbit-averaged stellar flux than its equator, so the poles are more likely to be covered in highly reflective snow and ice; and (2) we show that reflected light from a modest-obliquity planet at crescent phases probes higher latitudes than at gibbous phases, therefore a planet's apparent albedo will naturally increase at crescent phase. We suggest that this 'latitude-albedo effect' will operate even for large obliquities: in that case the equator receives less orbit-averaged flux than the poles, and the equator is preferentially sampled at crescent phase. Using rotational and orbital color variations to map the surfaces of directly imaged planets and estimate their obliquity will therefore be a necessary pre-condition for properly interpreting their reflected phase variations. The latitude-albedo effect is a particularly convincing glint false positive for zero-obliquity planets, and such worlds are not amenable to latitudinal mapping. This effect severely limits the utility of specular reflection for detecting oceans on exoplanets.

  20. Kepler Eclipsing Binary Stars. VIII. Identification of False Positive Eclipsing Binaries and Re-extraction of New Light Curves

    NASA Astrophysics Data System (ADS)

    Abdul-Masih, Michael; Prša, Andrej; Conroy, Kyle; Bloemen, Steven; Boyajian, Tabetha; Doyle, Laurance R.; Johnston, Cole; Kostov, Veselin; Latham, David W.; Matijevič, Gal; Shporer, Avi; Southworth, John

    2016-04-01

    The Kepler mission has provided unprecedented, nearly continuous photometric data of ∼200,000 objects in the ∼105 deg2 field of view (FOV) from the beginning of science operations in May of 2009 until the loss of the second reaction wheel in May of 2013. The Kepler Eclipsing Binary Catalog contains information including but not limited to ephemerides, stellar parameters, and analytical approximation fits for every known eclipsing binary system in the Kepler FOV. Using target pixel level data collected from Kepler in conjunction with the Kepler Eclipsing Binary Catalog, we identify false positives among eclipsing binaries, i.e., targets that are not eclipsing binaries themselves, but are instead contaminated by eclipsing binary sources nearby on the sky and show eclipsing binary signatures in their light curves. We present methods for identifying these false positives and for extracting new light curves for the true source of the observed binary signal. For each source, we extract three separate light curves for each quarter of available data by optimizing the signal-to-noise ratio, the relative percent eclipse depth, and the flux eclipse depth. We present 289 new eclipsing binaries in the Kepler FOV that were not targets for observation, and these have been added to the catalog. An online version of this catalog with downloadable content and visualization tools is maintained at http://keplerEBs.villanova.edu.

  1. Case Report: Direct Access Genetic Testing and A False-Positive Result For Long QT Syndrome.

    PubMed

    Predham, Sarah; Hamilton, Sara; Elliott, Alison M; T Gibson, William

    2016-02-01

    We report the case of a woman who pursued direct access genetic testing and then presented with concerns regarding a positive test result for Long-QT syndrome. Although the result ultimately proved to be a false positive, this case illustrates that costs associated with follow-up of direct access genetic testing results can be non-trivial for both the patient and for health care systems. Here we raise policy questions regarding the appropriate distribution of these costs. We also discuss the possibility that, when confronted by a direct access genetic test result that reports high risk for one or more actionable diseases, a family physician might feel compelled to act out of a desire to avoid liability, even when information regarding the accuracy and validity of the testing were not easily accessible. This case outlines lessons that can easily be translated into clinical practice, not only by genetic counselors, but also by family physicians, medical specialists and members of the public.

  2. A self-paced brain-computer interface system with a low false positive rate.

    PubMed

    Fatourechi, M; Ward, R K; Birch, G E

    2008-03-01

    The performance of current EEG-based self-paced brain-computer interface (SBCI) systems is not suitable for most practical applications. In this paper, an improved SBCI that uses features extracted from three neurological phenomena (movement-related potentials, changes in the power of Mu rhythms and changes in the power of Beta rhythms) to detect an intentional control command in noisy EEG signals is proposed. The proposed system achieves a high true positive (TP) to false positive (FP) ratio. To extract features for each neurological phenomenon in every EEG signal, a method that consists of a stationary wavelet transform followed by matched filtering is developed. For each neurological phenomenon in every EEG channel, features are classified using a support vector machine classifier (SVM). For each neurological phenomenon, a multiple classifier system (MCS) then combines the outputs of the SVMs. Another MCS combines the outputs of MCSs designed for the three neurological phenomena. Various configurations for combining the outputs of these MCSs are considered. A hybrid genetic algorithm (HGA) is proposed to simultaneously select the features, the values of the classifiers' parameters and the configuration for combining MCSs that yield the near optimal performance. Analysis of the data recorded from four able-bodied subjects shows a significant performance improvement over previous SBCIs.

  3. Transient elastography and APRI score: looking at false positives and false negatives. Diagnostic performance and association to fibrosis staging in chronic hepatitis C

    PubMed Central

    Mendes, L.C.; Ferreira, P.A.; Miotto, N.; Zanaga, L.; Gonçales, E.; Lazarini, M.S.; Gonçales, F.L.; Stucchi, R.S.B.; Vigani, A.G.

    2016-01-01

    Although long regarded as the gold standard for liver fibrosis staging in chronic hepatitis C (CHC), liver biopsy (LB) implies both the risk of an invasive procedure and significant variability. The aim of this study was to evaluate the diagnostic performance for transient elastography (TE) and aspartate aminotransferase to platelet index (APRI) used alone and in combination compared to liver biopsy and to analyze false positive/negative results. Patients with CHC, and no previous clinical diagnosis of cirrhosis were enrolled to undergo liver biopsy, TE and APRI. A total of 182 adult patients with a median age of 55 years and median body mass index of 26.71 kg/m2 were analyzed. On LB, 56% of patients had significant levels of fibrosis (METAVIR F≥2) and 28% had advanced fibrosis (F3/F4). The strongest performance for both tests was observed for exclusion of advanced fibrosis with good negative predictive values (89 and 86%, respectively). Low necroinflammatory activity on LB was associated with false negative TE. False positives were associated with NASH and smaller LB fragments. Correlation between APRI and Fibroscan for F≥2 was 100% and 84% for F≥3 and remained high in both false negative and false positive instances, correctly identifying F<2 in 71% of cases and F<3 in 78% (and potentially foregoing up to 84% of LB). We concluded that low individual performance indicators could be attributable to limitations of LB. Poorer differentiation of lower levels of fibrosis is a known issue for LB and remains so for noninvasive tests. Good predictability is possible, however, for advanced fibrosis. PMID:27533769

  4. VizieR Online Data Catalog: Kepler Mission. VIII. 285 false positives (Abdul-Masih+, 2016)

    NASA Astrophysics Data System (ADS)

    Abdul-Masih, M.; Prsa, A.; Conroy, K.; Bloemen, S.; Boyajian, T.; Doyle, L. R.; Johnston, C.; Kostov, V.; Latham, D. W.; Matijevic, G.; Shporer, A.; Southworth, J.

    2016-08-01

    The Kepler mission was launched in 2009 and provided photometric data for ~200000 objects in the 105deg2 contained in the Kepler field of view (FOV; Batalha et al. 2013, Cat. J/ApJS/204/24). Each of the 95 million Kepler pixels cover 3.98*3.98'' and are designed to maximize the number of resolvable stars with magnitudes brighter than 15. There are approximately 500000 objects in the Kepler FOV that are brighter than V=16; however, only ~200000 were assigned as targets for observation, leaving many bright objects in the field unobserved. Since the main goal of Kepler is to find Earth-sized planets in the habitable zone of Sun-like stars, the targets that were chosen for observation were those with the highest potential for terrestrial planet detection. Thus, many objects in the Kepler FOV have not been observed. Due to the proximity of some of these unobserved objects to the identified targets, the possibility of contaminated signals arises. Of the observed targets, 2772 eclipsing binaries have been found and cataloged in the Kepler Eclipsing Binary Catalog (http://keplerebs.villanova.edu/; see also Kirk et al. 2016, Cat. J/AJ/151/68). A false positive is a case where the signal from a binary object in close proximity to a target contaminates the aperture pixels, causing the target light curve to show a binary signal. This means that the incorrect object is being identified as the source of the binary signal. Once the source of the binary signal is identified, a new light curve can be extracted. The re-extraction process is comprised of several automated steps and results in three new light curves generated for the true source of the binary signal for each quarter of available data. These light curves are generated by optimizing the signal-to-noise ratio (S/N light curve), percent eclipse depth (PED light curve), and flux eclipse depth (FED light curve). Before re-extracting the new light curves, we obtain the S/N, the PED, and the FED for the original false

  5. Astrophysical false positives in direct imaging for exoplanets: a white dwarf close to a rejuvenated star

    NASA Astrophysics Data System (ADS)

    Zurlo, A.; Vigan, A.; Hagelberg, J.; Desidera, S.; Chauvin, G.; Almenara, J. M.; Biazzo, K.; Bonnefoy, M.; Carson, J. C.; Covino, E.; Delorme, P.; D'Orazi, V.; Gratton, R.; Mesa, D.; Messina, S.; Moutou, C.; Segransan, D.; Turatto, M.; Udry, S.; Wildi, F.

    2013-06-01

    Context. As is the case for all techniques involved in the research for exoplanets, direct imaging has to take into account the probability of so-called astrophysical false positives, which are phenomena that mimic the signature of the objects we are seeking. Aims: In this work we present the case of a false positive found during a direct-imaging survey conducted with VLT/NACO. A promising exoplanet candidate was detected around the K2-type star HD 8049 in July 2010. Its contrast of ΔH = 7.05 at 1.57 arcsec allowed us to assume a 35 MJup companion at 50 projected AU, for the nominal system age and heliocentric distance. Methods: To check whether it was gravitationally bound to the host star, as opposed to an unrelated background object, we re-observed the system one year later and concluded a high probability of a bound system. We also used radial velocity measurements of the host star, spanning a time range of ~30 yr, to constrain the companion's mass and orbital properties, as well as to probe the host star's spectral age indicators and general spectral energy distribution. We also obtained U-band imaging with EFOSC and near-infrared spectroscopy for the companion. Results: Combining all these information we conclude that the companion of HD 8049 is a white dwarf (WD) with temperature Teff = 18 800 ± 2100 K and mass MWD = 0.56 ± 0.08 M⊙. The significant radial velocity trend combined with the imaging data indicates that the most probable orbit has a semi-major axis of about 50 AU. The discrepancy between the age indicators speaks against a bona-fide young star. The moderately high level of chromospheric activity and fast rotation, mimicking the properties of a young star, might be induced by the exchange of mass with the progenitor of the WD. This example demonstrates some of the challenges in determining accurate age estimates and identifications of faint companions. Based on observations collected at La Silla and Paranal Observatory, ESO (Chile): Programs

  6. False-positive diatom test: a real challenge? A post-mortem study using standardized protocols.

    PubMed

    Lunetta, Philippe; Miettinen, Arto; Spilling, Kristian; Sajantila, Antti

    2013-09-01

    The main criticism of the validity of the diatom test for the diagnosis of drowning is based on the potential ante- and post-mortem penetration of diatoms and the finding of diatoms in bodies of non-drowned human beings. However, qualitative and quantitative studies on diatoms in organs of the non-drowned have yielded both conflicting and contradictory results. In the present study, we have analysed under standardised methods the diatom content in several organs of 14 non-drowned human bodies. Overall, only 9 diatoms (6 entire, 3 fragmented) were disclosed in 6 of the 14 non-drowned bodies. Each of these 6 cadavers had only a single "positive" organ. Six diatoms were found in the bone marrow, 2 in the lung, and one in the pleural liquid. No diatoms were recovered from the brain, liver, kidney, or blood samples of any of these 14 bodies. Moreover, in five additional cadavers, whose lungs were injected, prior autopsy, with a 3.5L solution containing a bi-cellulate diatom culture (Thalassiosira baltica, Thalassiosira levanderi) via tracheostomy, a few diatoms appeared in the pleural cavity and in the blood from the left heart chamber, but none in any other internal organs investigated. The results of the presented study demonstrate that the issue of the false-positive diatom test should not be a logical impediment to the performance of the diatom method. However, strict and standardized protocols aimed at avoiding contamination during sample preparation must be used, appropriate separation values set and taxonomic analysis of all diatoms performed. PMID:23701706

  7. False-positive rapid plasma reagin testing in patients with acute Plasmodium vivax malaria: a case control study.

    PubMed

    Maves, Ryan C; Dean, Katherine; Gadea, Nilda; Halsey, Eric S; Graf, Paul C F; Lescano, Andres G

    2014-01-01

    Non-treponemal tests such as the rapid plasma reagin (RPR) assay are mainstays of syphilis diagnosis, but false-positive tests are common. We identified false-positive RPR titers in 8.2% of patients with malaria due to Plasmodium vivax in northern Peru. Similar rates were not detected in patients with other acute febrile illnesses.

  8. The uterine blush. A potential false-positive in Meckel's scan interpretation

    SciTech Connect

    Fink-Bennett, D.

    1982-10-01

    To determine the presence, prevalence, and clinical importance of /sup 99m/Tc pertechnetate uterine uptake, this retrospective analysis of 71 Meckel's scans was undertaken. Specifically, each study was evaluated for the presence of a focal accumulation of radiotracer cephalad to the bladder. Patients received an intravenous dose of 150 microCi/kg of /sup 99m/Tc pertechnetate. Each study consisted of 15 one minute anterior serial gamma camera images, and a 15, 30, and 60 minute anterior, right lateral and posterior scintiscan. Menstrual histories were obtained from all patients except two. No males (33/33), nor premenstrual (13/13), menopausal (4/4) or posthysterectomy (2/2) patients revealed a uterine blush. Eleven of 15 patients (73%) with regular menses demonstrated a uterine blush. They were in the menstrual or secretory phases of their cycle. Four demonstrated no uterine uptake, had regular periods, but were in the proliferative phase of their cycle. Two with irregular periods, and one with no recorded menstrual history, manifested the blush. Radiotracer should be expected in the uterus during the menstrual and secretory phases of the menstrual cycle. It is a manifestation of a normal physiologic phenomenon, and must be recognized to prevent false-positive Meckel's scan interpretations.

  9. THE POSSIBLE MOON OF KEPLER-90g IS A FALSE POSITIVE

    SciTech Connect

    Kipping, D. M.; Torres, G.; Buchhave, L. A.; Huang, X.; Bakos, G. Á.; Nesvorný, D.; Schmitt, A. R.

    2015-01-20

    The discovery of an exomoon would provide deep insights into planet formation and the habitability of planetary systems, with transiting examples being particularly sought after. Of the hundreds of Kepler planets now discovered, the seven-planet system Kepler-90 is unusual for exhibiting an unidentified transit-like signal in close proximity to one of the transits of the long-period gas-giant Kepler-90g, as noted by Cabrera et al. As part of the ''Hunt for Exomoons with Kepler'' project, we investigate this possible exomoon signal and find it passes all conventional photometric, dynamical, and centroid diagnostic tests. However, pixel-level light curves indicate that the moon-like signal occurs on nearly all of the target's pixels, which we confirm using a novel way of examining pixel-level data which we dub the ''transit centroid''. This test reveals that the possible exomoon to Kepler-90g is likely a false positive, perhaps due to a cosmic ray induced sudden pixel sensitivity dropout. This work highlights the extreme care required for seeking non-periodic low-amplitude transit signals, such as exomoons.

  10. Computerized detection of unruptured aneurysms in MRA images: reduction of false positives using anatomical location features

    NASA Astrophysics Data System (ADS)

    Uchiyama, Yoshikazu; Gao, Xin; Hara, Takeshi; Fujita, Hiroshi; Ando, Hiromichi; Yamakawa, Hiroyasu; Asano, Takahiko; Kato, Hiroki; Iwama, Toru; Kanematsu, Masayuki; Hoshi, Hiroaki

    2008-03-01

    The detection of unruptured aneurysms is a major subject in magnetic resonance angiography (MRA). However, their accurate detection is often difficult because of the overlapping between the aneurysm and the adjacent vessels on maximum intensity projection images. The purpose of this study is to develop a computerized method for the detection of unruptured aneurysms in order to assist radiologists in image interpretation. The vessel regions were first segmented using gray-level thresholding and a region growing technique. The gradient concentration (GC) filter was then employed for the enhancement of the aneurysms. The initial candidates were identified in the GC image using a gray-level threshold. For the elimination of false positives (FPs), we determined shape features and an anatomical location feature. Finally, rule-based schemes and quadratic discriminant analysis were employed along with these features for distinguishing between the aneurysms and the FPs. The sensitivity for the detection of unruptured aneurysms was 90.0% with 1.52 FPs per patient. Our computerized scheme can be useful in assisting the radiologists in the detection of unruptured aneurysms in MRA images.

  11. College football, elections, and false-positive results in observational research

    PubMed Central

    Fowler, Anthony; Montagnes, B. Pablo

    2015-01-01

    A recent, widely cited study [Healy AJ, Malhotra N, Mo CH (2010) Proc Natl Acad Sci USA 107(29):12804–12809] finds that college football games influence voting behavior. Victories within 2 weeks of an election reportedly increase the success of the incumbent party in presidential, senatorial, and gubernatorial elections in the home county of the team. We reassess the evidence and conclude that there is likely no such effect, despite the fact that Healy et al. followed the best practices in social science and used a credible research design. Multiple independent sources of evidence suggest that the original finding was spurious—reflecting bad luck for researchers rather than a shortcoming of American voters. We fail to estimate the same effect when we leverage situations where multiple elections with differing incumbent parties occur in the same county and year. We also find that the purported effect of college football games is stronger in counties where people are less interested in college football, just as strong when the incumbent candidate does not run for reelection, and just as strong in other parts of the state outside the home county of the team. Lastly, we detect no effect of National Football League games on elections, despite their greater popularity. We conclude with recommendations for evaluating surprising research findings and avoiding similar false-positive results. PMID:26504202

  12. Collagen and elastin histochemistry of the teleost bulbus arteriosus: false positives.

    PubMed

    Icardo, José M

    2013-03-01

    This report analyzes the localization of collagen and elastin in the teleost bulbus arteriosus by histochemistry and by transmission electron microscopy. Martin's trichrome staining shows widespread distribution of collagen in the wall of the bulbus. However, Sirius red indicates that collagen is mostly restricted to the valves and to the subepicardial layer. This is confirmed by transmission electron microscopy. Trichrome staining gives false positives that may be related to the chemical characteristics of both matrix components and dyes. By contrast, Sirius red constitutes a highly reliable method to detect collagen distribution. On the other hand, orcein heavily stains the bulbus of all teleosts examined. This includes the bulbus of the Antarctic teleosts, which do not show structurally discernable elastin fibers. In these cases, orcein may be staining non-elastin components, or basic elastin components not assembled into larger units. In the teleost bulbus, accurate identification of collagen and elastin cannot be based solely on histochemistry, but should be accompanied by structural identification of the components under study.

  13. College football, elections, and false-positive results in observational research.

    PubMed

    Fowler, Anthony; Montagnes, B Pablo

    2015-11-10

    A recent, widely cited study [Healy AJ, Malhotra N, Mo CH (2010) Proc Natl Acad Sci USA 107(29):12804-12809] finds that college football games influence voting behavior. Victories within 2 weeks of an election reportedly increase the success of the incumbent party in presidential, senatorial, and gubernatorial elections in the home county of the team. We reassess the evidence and conclude that there is likely no such effect, despite the fact that Healy et al. followed the best practices in social science and used a credible research design. Multiple independent sources of evidence suggest that the original finding was spurious-reflecting bad luck for researchers rather than a shortcoming of American voters. We fail to estimate the same effect when we leverage situations where multiple elections with differing incumbent parties occur in the same county and year. We also find that the purported effect of college football games is stronger in counties where people are less interested in college football, just as strong when the incumbent candidate does not run for reelection, and just as strong in other parts of the state outside the home county of the team. Lastly, we detect no effect of National Football League games on elections, despite their greater popularity. We conclude with recommendations for evaluating surprising research findings and avoiding similar false-positive results.

  14. Controlling false positive rates in mass-multivariate tests for electromagnetic responses

    PubMed Central

    Barnes, Gareth R.; Litvak, Vladimir; Brookes, Matt J.; Friston, Karl J.

    2011-01-01

    We address the problem of controlling false positive rates in mass-multivariate tests for electromagnetic responses in compact regions of source space. We show that mass-univariate thresholds based on sensor level multivariate thresholds (approximated using Roy's union–intersection principle) are unduly conservative. We then consider a Bonferroni correction for source level tests based on the number of unique lead-field extrema. For a given source space, the sensor indices corresponding to the maxima and minima (for each dipolar lead field) are listed, and the number of unique extrema is given by the number of unique pairs in this list. Using a multivariate beamformer formulation, we validate this heuristic against empirical permutation thresholds for mass-univariate and mass-multivariate tests (of induced and evoked responses) for a variety of source spaces, using simulated and real data. We also show that the same approximations hold when dealing with a cortical manifold (rather than a volume) and for mass-multivariate minimum norm solutions. We demonstrate that the mass-multivariate framework is not restricted to tests on a single contrast of effects (cf, Roy's maximum root) but also accommodates multivariate effects (cf, Wilk's lambda). PMID:21396458

  15. Controlling false positive rates in mass-multivariate tests for electromagnetic responses.

    PubMed

    Barnes, Gareth R; Litvak, Vladimir; Brookes, Matt J; Friston, Karl J

    2011-06-01

    We address the problem of controlling false positive rates in mass-multivariate tests for electromagnetic responses in compact regions of source space. We show that mass-univariate thresholds based on sensor level multivariate thresholds (approximated using Roy's union-intersection principle) are unduly conservative. We then consider a Bonferroni correction for source level tests based on the number of unique lead-field extrema. For a given source space, the sensor indices corresponding to the maxima and minima (for each dipolar lead field) are listed, and the number of unique extrema is given by the number of unique pairs in this list. Using a multivariate beamformer formulation, we validate this heuristic against empirical permutation thresholds for mass-univariate and mass-multivariate tests (of induced and evoked responses) for a variety of source spaces, using simulated and real data. We also show that the same approximations hold when dealing with a cortical manifold (rather than a volume) and for mass-multivariate minimum norm solutions. We demonstrate that the mass-multivariate framework is not restricted to tests on a single contrast of effects (cf, Roy's maximum root) but also accommodates multivariate effects (cf, Wilk's lambda).

  16. Risk of false positive genetic associations in complex traits with underlying population structure: A case study

    PubMed Central

    Finno, Carrie J.; Aleman, Monica; Higgins, Robert J.; Madigan, John E.; Bannasch, Danika L.

    2015-01-01

    Genome-wide association (GWA) studies are widely used to investigate the genetic etiology of diseases in domestic animals. In the horse, GWA studies using 40–50,000 single nucleotide polymorphisms (SNPs) in sample sizes of 30–40 individuals, consisting of only 6–14 affected horses, have led to the discovery of genetic mutations for simple monogenic traits. Equine neuroaxonal dystrophy is a common inherited neurological disorder characterized by symmetric ataxia. A case-control GWA study was performed using genotypes from 42,819 SNP marker loci distributed across the genome in 99 clinically phenotyped Quarter horses (37 affected, 62 unaffected). A significant GWA was not achieved although a suggestive association was uncovered when only the most stringently phenotyped NAD-affected horses (n = 10) were included (chromosome 8:62130605 and 62134644 [log(1/P) = 5.56]). Candidate genes (PIK3C3, RIT2, and SYT4) within the associated region were excluded through sequencing, association testing of uncovered variants and quantitative RT-PCR. It was concluded that variants in PIK3C3, RIT2, and SYT4 are not responsible for equine neuroaxonal dystrophy. This study demonstrates the risk of false positive associations when performing GWA studies on complex traits and underlying population structure when using 40–50,000 SNP markers and small sample size. PMID:25278384

  17. The Possible Moon of Kepler-90g is a False Positive

    NASA Astrophysics Data System (ADS)

    Kipping, D. M.; Huang, X.; Nesvorný, D.; Torres, G.; Buchhave, L. A.; Bakos, G. Á.; Schmitt, A. R.

    2015-01-01

    The discovery of an exomoon would provide deep insights into planet formation and the habitability of planetary systems, with transiting examples being particularly sought after. Of the hundreds of Kepler planets now discovered, the seven-planet system Kepler-90 is unusual for exhibiting an unidentified transit-like signal in close proximity to one of the transits of the long-period gas-giant Kepler-90g, as noted by Cabrera et al. As part of the "Hunt for Exomoons with Kepler" project, we investigate this possible exomoon signal and find it passes all conventional photometric, dynamical, and centroid diagnostic tests. However, pixel-level light curves indicate that the moon-like signal occurs on nearly all of the target's pixels, which we confirm using a novel way of examining pixel-level data which we dub the "transit centroid." This test reveals that the possible exomoon to Kepler-90g is likely a false positive, perhaps due to a cosmic ray induced sudden pixel sensitivity dropout. This work highlights the extreme care required for seeking non-periodic low-amplitude transit signals, such as exomoons.

  18. Cumulative risk of false positive test in relation to breast symptoms in mammography screening: a historical prospective cohort study.

    PubMed

    Singh, Deependra; Pitkäniemi, Janne; Malila, Nea; Anttila, Ahti

    2016-09-01

    Mammography has been found effective as the primary screening test for breast cancer. We estimated the cumulative probability of false positive screening test results with respect to symptom history reported at screen. A historical prospective cohort study was done using individual screening data from 413,611 women aged 50-69 years with 2,627,256 invitations for mammography screening between 1992 and 2012 in Finland. Symptoms (lump, retraction, and secretion) were reported at 56,805 visits, and 48,873 visits resulted in a false positive mammography result. Generalized linear models were used to estimate the probability of at least one false positive test and true positive at screening visits. The estimates were compared among women with and without symptoms history. The estimated cumulative probabilities were 18 and 6 % for false positive and true positive results, respectively. In women with a history of a lump, the cumulative probabilities of false positive test and true positive were 45 and 16 %, respectively, compared to 17 and 5 % with no reported lump. In women with a history of any given symptom, the cumulative probabilities of false positive test and true positive were 38 and 13 %, respectively. Likewise, women with a history of a 'lump and retraction' had the cumulative false positive probability of 56 %. The study showed higher cumulative risk of false positive tests and more cancers detected in women who reported symptoms compared to women who did not report symptoms at screen. The risk varies substantially, depending on symptom types and characteristics. Information on breast symptoms influences the balance of absolute benefits and harms of screening. PMID:27496148

  19. Cumulative risk of false positive test in relation to breast symptoms in mammography screening: a historical prospective cohort study.

    PubMed

    Singh, Deependra; Pitkäniemi, Janne; Malila, Nea; Anttila, Ahti

    2016-09-01

    Mammography has been found effective as the primary screening test for breast cancer. We estimated the cumulative probability of false positive screening test results with respect to symptom history reported at screen. A historical prospective cohort study was done using individual screening data from 413,611 women aged 50-69 years with 2,627,256 invitations for mammography screening between 1992 and 2012 in Finland. Symptoms (lump, retraction, and secretion) were reported at 56,805 visits, and 48,873 visits resulted in a false positive mammography result. Generalized linear models were used to estimate the probability of at least one false positive test and true positive at screening visits. The estimates were compared among women with and without symptoms history. The estimated cumulative probabilities were 18 and 6 % for false positive and true positive results, respectively. In women with a history of a lump, the cumulative probabilities of false positive test and true positive were 45 and 16 %, respectively, compared to 17 and 5 % with no reported lump. In women with a history of any given symptom, the cumulative probabilities of false positive test and true positive were 38 and 13 %, respectively. Likewise, women with a history of a 'lump and retraction' had the cumulative false positive probability of 56 %. The study showed higher cumulative risk of false positive tests and more cancers detected in women who reported symptoms compared to women who did not report symptoms at screen. The risk varies substantially, depending on symptom types and characteristics. Information on breast symptoms influences the balance of absolute benefits and harms of screening.

  20. Limited Agreement of Independent RNAi Screens for Virus-Required Host Genes Owes More to False-Negative than False-Positive Factors

    PubMed Central

    Wang, Zhishi; Craven, Mark; Newton, Michael A.; Ahlquist, Paul

    2013-01-01

    Systematic, genome-wide RNA interference (RNAi) analysis is a powerful approach to identify gene functions that support or modulate selected biological processes. An emerging challenge shared with some other genome-wide approaches is that independent RNAi studies often show limited agreement in their lists of implicated genes. To better understand this, we analyzed four genome-wide RNAi studies that identified host genes involved in influenza virus replication. These studies collectively identified and validated the roles of 614 cell genes, but pair-wise overlap among the four gene lists was only 3% to 15% (average 6.7%). However, a number of functional categories were overrepresented in multiple studies. The pair-wise overlap of these enriched-category lists was high, ∼19%, implying more agreement among studies than apparent at the gene level. Probing this further, we found that the gene lists implicated by independent studies were highly connected in interacting networks by independent functional measures such as protein-protein interactions, at rates significantly higher than predicted by chance. We also developed a general, model-based approach to gauge the effects of false-positive and false-negative factors and to estimate, from a limited number of studies, the total number of genes involved in a process. For influenza virus replication, this novel statistical approach estimates the total number of cell genes involved to be ∼2,800. This and multiple other aspects of our experimental and computational results imply that, when following good quality control practices, the low overlap between studies is primarily due to false negatives rather than false-positive gene identifications. These results and methods have implications for and applications to multiple forms of genome-wide analysis. PMID:24068911

  1. Overcoming the effects of false positives and threshold bias in graph theoretical analyses of neuroimaging data

    PubMed Central

    Drakesmith, M.; Caeyenberghs, K.; Dutt, A.; Lewis, G.; David, A.S.; Jones, D.K.

    2015-01-01

    Graph theory (GT) is a powerful framework for quantifying topological features of neuroimaging-derived functional and structural networks. However, false positive (FP) connections arise frequently and influence the inferred topology of networks. Thresholding is often used to overcome this problem, but an appropriate threshold often relies on a priori assumptions, which will alter inferred network topologies. Four common network metrics (global efficiency, mean clustering coefficient, mean betweenness and smallworldness) were tested using a model tractography dataset. It was found that all four network metrics were significantly affected even by just one FP. Results also show that thresholding effectively dampens the impact of FPs, but at the expense of adding significant bias to network metrics. In a larger number (n = 248) of tractography datasets, statistics were computed across random group permutations for a range of thresholds, revealing that statistics for network metrics varied significantly more than for non-network metrics (i.e., number of streamlines and number of edges). Varying degrees of network atrophy were introduced artificially to half the datasets, to test sensitivity to genuine group differences. For some network metrics, this atrophy was detected as significant (p < 0.05, determined using permutation testing) only across a limited range of thresholds. We propose a multi-threshold permutation correction (MTPC) method, based on the cluster-enhanced permutation correction approach, to identify sustained significant effects across clusters of thresholds. This approach minimises requirements to determine a single threshold a priori. We demonstrate improved sensitivity of MTPC-corrected metrics to genuine group effects compared to an existing approach and demonstrate the use of MTPC on a previously published network analysis of tractography data derived from a clinical population. In conclusion, we show that there are large biases and instability

  2. False positive reduction of microcalcification cluster detection in digital breast tomosynthesis

    NASA Astrophysics Data System (ADS)

    Xu, Ning; Yi, Sheng; Mendonca, Paulo; Tian, Tai-peng; Samala, Ravi; Chan, Heang-Ping

    2014-03-01

    Digital breast tomosynthesis (DBT) is a new modality that has strong potential in improving the sensitivity and specificity of breast mass detection. However, the detection of microcalcifications (MCs) in DBT is challenging because radiologists have to search for the often subtle signals in many slices. We are developing a computer-aided detection (CAD) system to assist radiologists in reading DBT. The system consists of four major steps, namely: image enhancement; pre-screening of MC candidates; false-positive (FP) reduction, and detection of MC cluster candidates of clinical interest. We propose an algorithm for reducing FPs by using 3D characteristics of MC clusters in DBT. The proposed method takes the MC candidates from the pre-screening step described in [14] as input, which are then iteratively clustered to provide training samples to a random-forest classifier and a rule-based classifier. The random forest classifier is used to learn a discriminative model of MC clusters using 3D texture features, whereas the rule-based classifier revisits the initial training samples and enhances them by combining median filtering and graph-cut-based segmentation followed by thresholding on the final number of MCs belonging to the candidate cluster. The outputs of these two classifiers are combined according to the prediction confidence of the random-forest classifier. We evaluate the proposed FP-reduction algorithm on a data set of two-view DBT from 40 breasts with biopsy-proven MC clusters. The experimental results demonstrate a significant reduction in FP detections, with a final sensitivity of 92.2% for an FP rate of 50%.

  3. Prostate-Specific Membrane Antigen PET/CT: False-Positive Results due to Sarcoidosis?

    PubMed Central

    Hermann, Robert M.; Djannatian, Manoutschehr; Czech, Norbert; Nitsche, Mirko

    2016-01-01

    We report on a 72-year-old male patient who developed sarcoidosis of the mediastinal lymph nodes, the liver, and the prostate 11 years ago. Seven years later, he underwent transurethral resection of the prostate by laser due to hematuria. Pathology of the resected chips showed a ‘granulomatous prostatitis with epitheloid cells’. Malignancy was histologically excluded at that time. Four years later, he was diagnosed with an undifferentiated prostate carcinoma, with a Gleason score of 5 + 4 = 9. After initiation of antihormonal therapy, he underwent radical prostatectomy and pelvic lymphadenectomy, which revealed a pT3b pN1 carcinoma with infiltrated resection margins. Three months later, the prostate-specific antigen level was 1.4 ng/ml, and a local recurrence was suspected by ultrasound; consequently, a 68Ga-prostate-specific membrane antigen (PSMA) PET/CT was performed. This examination seemed to confirm the local recurrence, a right pelvic lymph node metastasis, and a hepatic metastasis. However, ultrasound with contrast medium could not confirm the metastatic spread to the liver. In palliative intention, radiotherapy of the pelvis was done. After 50 Gy, the supposed recurrence had markedly shrunk, and an additional boost dose with 16.2 Gy was applied. Two years later, the patient is still free of disease. Due to this clinical development, we doubt the diagnosis of a fulminant progression of the prostate cancer as suspected by PSMA-PET/CT. Instead, we suspect a recurrence of the previously proven sarcoidosis leading to false-positive results. Our focus in this report is on the interaction between PSMA-PET/CT and sarcoidosis. Another report on a case of sarcoidosis of the spleen seems to confirm this possibility [Kobe et al: Clin Nucl Med 2015;40: 897–898]. PMID:27721768

  4. Signature of life on exoplanets: Can Darwin produce false positive detections?

    NASA Astrophysics Data System (ADS)

    Selsis, F.; Despois, D.; Parisot, J.-P.

    2002-06-01

    Darwin (ESA) and Terrestrial Planet Finder-TPF (NASA) are two projects of space telescopes aiming at the detection of extra-solar terrestrial planets and some of their atmospheric components. In particular, they will be sensitive to the 9.6 mu m band of O3 which may be the signature of an O2 -rich atmosphere produced by photosynthetic life forms. In this paper, we point out that O2 , and hence O3 , can also be produced by photochemistry and we investigate the risk of ``false positive'' detection of life incurred by these missions. For this purpose, we have developed new photochemical and radiative-convective models of terrestrial planet atmospheres. By modelling the photochemistry of some realistic atmospheres, (including present and past Earth and Mars) we show that O2 -rich atmospheres (up to 5%) and IR absorbing O3 layers can build up without life from H2O and CO2 photolysis. However, Darwin can still provide a reliable way to detect, through their mid-infrared signatures, ecosystems which have developed oxygenic photosynthesis. Indeed, the two photochemical sources of O2 are shown to interfere with each other; second, when the CO2 pressure is high enough (>50 mbar) to produce appreciable amounts of O2 and O3 , it also masks the O3 feature; and third, the by-products of H2O photolysis destroy O3 . As a result, whereas the unique detection of O2 remains ambiguous, the simultaneous infrared detection of O3 , CO2 and H2O , provided by Darwin, is established to be a robust way to discriminate photochemical O2 production from biological photosynthesis: none of the atmospheres modelled exhibits this ``triple signature'', even in the most extreme ``high risk'' cases.

  5. Overcoming the effects of false positives and threshold bias in graph theoretical analyses of neuroimaging data.

    PubMed

    Drakesmith, M; Caeyenberghs, K; Dutt, A; Lewis, G; David, A S; Jones, D K

    2015-09-01

    Graph theory (GT) is a powerful framework for quantifying topological features of neuroimaging-derived functional and structural networks. However, false positive (FP) connections arise frequently and influence the inferred topology of networks. Thresholding is often used to overcome this problem, but an appropriate threshold often relies on a priori assumptions, which will alter inferred network topologies. Four common network metrics (global efficiency, mean clustering coefficient, mean betweenness and smallworldness) were tested using a model tractography dataset. It was found that all four network metrics were significantly affected even by just one FP. Results also show that thresholding effectively dampens the impact of FPs, but at the expense of adding significant bias to network metrics. In a larger number (n=248) of tractography datasets, statistics were computed across random group permutations for a range of thresholds, revealing that statistics for network metrics varied significantly more than for non-network metrics (i.e., number of streamlines and number of edges). Varying degrees of network atrophy were introduced artificially to half the datasets, to test sensitivity to genuine group differences. For some network metrics, this atrophy was detected as significant (p<0.05, determined using permutation testing) only across a limited range of thresholds. We propose a multi-threshold permutation correction (MTPC) method, based on the cluster-enhanced permutation correction approach, to identify sustained significant effects across clusters of thresholds. This approach minimises requirements to determine a single threshold a priori. We demonstrate improved sensitivity of MTPC-corrected metrics to genuine group effects compared to an existing approach and demonstrate the use of MTPC on a previously published network analysis of tractography data derived from a clinical population. In conclusion, we show that there are large biases and instability induced

  6. Racial Differences in False-Positive Mammogram Rates: Results from the ACRIN Digital Mammographic Imaging Screening Trial (DMIST)

    PubMed Central

    McCarthy, Anne Marie; Yamartino, Philip; Yang, Jianing; Bristol, Mirar; Conant, Emily; Armstrong, Katrina

    2015-01-01

    Background Mammography screening reduces breast cancer mortality, but false-positive tests are common. Few studies have assessed racial differences in false-positive rates. Objectives We compared false-positive mammography rates for black and white women, and the effect of patient and facility characteristics on false-positives. Research Design and Subjects Prospective cohort study. From a sample of the American College of Radiology Imaging Network (ACRIN) Digital Mammographic Imaging Screening Trial (DMIST), we identified black/African American (N=3176) or white (N=26,446) women with no prior breast surgery or breast cancer. Measures Race, demographics, and breast cancer risk factors were self-reported. Results of initial digital and film mammograms were assessed. False-positives were defined as a positive mammogram (Breast Imaging Reporting and Data System [BIRADS] category 0, 4, 5) with no cancer diagnosis within 15 months. Results The false-positive rate for digital mammograms was 9.2% for black women compared to 7.8% for white women (p=0.009). After adjusting for age, black women had 17% increased odds of false-positive digital mammogram compared to whites (OR=1.17, 95% CI 1.01-1.35, p=0.033). This association was attenuated after adjusting for patient factors, prior films and study site (OR=1.04, 95% CI 0.91-1.20, p=0.561). There was no difference in the occurrence of false-positives by race for film mammography. Conclusion Black women had higher frequency of false-positive digital mammograms explained by lack of prior films and study site.The variation in the disparity between the established technique (film) and the new technology (digital) raises the possibility that racial differences in screening quality may be greatest for new technologies. PMID:26125419

  7. False-Positive Mycobacterium tuberculosis Cultures in 44 Laboratories in The Netherlands (1993 to 2000): Incidence, Risk Factors, and Consequences

    PubMed Central

    de Boer, Annette S.; Blommerde, Barbara; de Haas, Petra E. W.; Sebek, Maruschka M. G. G.; Lambregts-van Weezenbeek, Kitty S. B.; Dessens, Mirjam; van Soolingen, Dick

    2002-01-01

    False-positive Mycobacterium tuberculosis cultures are a benchmark for the quality of laboratory processes and patient care. We studied the incidence of false-positive cultures, risk factors, and consequences for patients during the period from 1993 to 2000 in 44 peripheral laboratories in The Netherlands. The national reference laboratory tested 8,889 M. tuberculosis isolates submitted by these laboratories. By definition, a culture was false positive (i) if the DNA fingerprint of the isolate was identical to that of an isolate from another patient processed within 7 days in the same laboratory, (ii) if the isolate was taken from a patient without clinical signs of tuberculosis, and/or (iii) if the false-positive test result was confirmed by the peripheral laboratory and/or the public health tuberculosis officer. We identified 213 false-positive cultures (2.4%). The overall incidence of false-positive cultures decreased over the years, from 3.9% in 1993 to 1.1% in 2000. Laboratories with false-positive cultures more often processed less than 3,000 samples per year (P < 0.05). Among 110 patients for whom a false-positive culture was identified from 1995 to 1999, we found that for 36% of the patients an official tuberculosis notification had been provided to the appropriate public health services, 31% of the patients were treated, 14% of the patients were hospitalized, and a contact investigation had been initiated for 16% of the patients. The application of DNA fingerprinting to identify false-positive M. tuberculosis cultures and the provision of feedback to peripheral laboratories are useful instruments to improve the quality of laboratory processes and the quality of medical care. PMID:12409366

  8. False-positive mycobacterium tuberculosis cultures in 44 laboratories in The Netherlands (1993 to 2000): incidence, risk factors, and consequences.

    PubMed

    de Boer, Annette S; Blommerde, Barbara; de Haas, Petra E W; Sebek, Maruschka M G G; Lambregts-van Weezenbeek, Kitty S B; Dessens, Mirjam; van Soolingen, Dick

    2002-11-01

    False-positive Mycobacterium tuberculosis cultures are a benchmark for the quality of laboratory processes and patient care. We studied the incidence of false-positive cultures, risk factors, and consequences for patients during the period from 1993 to 2000 in 44 peripheral laboratories in The Netherlands. The national reference laboratory tested 8,889 M. tuberculosis isolates submitted by these laboratories. By definition, a culture was false positive (i) if the DNA fingerprint of the isolate was identical to that of an isolate from another patient processed within 7 days in the same laboratory, (ii) if the isolate was taken from a patient without clinical signs of tuberculosis, and/or (iii) if the false-positive test result was confirmed by the peripheral laboratory and/or the public health tuberculosis officer. We identified 213 false-positive cultures (2.4%). The overall incidence of false-positive cultures decreased over the years, from 3.9% in 1993 to 1.1% in 2000. Laboratories with false-positive cultures more often processed less than 3,000 samples per year (P < 0.05). Among 110 patients for whom a false-positive culture was identified from 1995 to 1999, we found that for 36% of the patients an official tuberculosis notification had been provided to the appropriate public health services, 31% of the patients were treated, 14% of the patients were hospitalized, and a contact investigation had been initiated for 16% of the patients. The application of DNA fingerprinting to identify false-positive M. tuberculosis cultures and the provision of feedback to peripheral laboratories are useful instruments to improve the quality of laboratory processes and the quality of medical care.

  9. The Illusion of the Positive: The impact of natural and induced mood on older adults’ false recall

    PubMed Central

    Emery, Lisa; Hess, Thomas M.; Elliot, Tonya

    2012-01-01

    Recent research suggests that affective and motivational processes can influence age differences in memory. In the current study, we examine the impact of both natural and induced mood state on age differences in false recall. Older and younger adults performed a version of the Deese-Roediger-McDermott (DRM; Roediger & McDermott, 1995) false memory paradigm in either their natural mood state or after a positive or negative mood induction. Results indicated that, after accounting for age differences in basic cognitive function, age-related differences in positive mood during the testing session were related to increased false recall in older adults. Inducing older adults into a positive mood also exacerbated age differences in false memory. In contrast, veridical recall did not appear to be systematically influenced by mood. Together, these results suggest that positive mood states can impact older adults’ information processing and potentially increase underlying cognitive age differences. PMID:22292431

  10. Indium-111 leukocyte accumulation in submandibular gland saliva as a cause for false-positive gut uptake in children

    SciTech Connect

    Williamson, S.L.; Williamson, M.R.; Seibert, J.J.; Boyd, C.M.; Latture, T.

    1987-11-01

    Unexplained false-positive accumulation of In-111 leukocyte in the gastrointestinal tract has been reported previously. In a pediatric population, uptake in the submandibular gland was noted in 19 of 42 children. This is believed to be a normal finding in children that is not seen in adults. In some of these 19 children, unexplained gastrointestinal activity was also noted. Saliva from a patient with false-positive gastrointestinal uptake and positive submandibular activity was positive for In-111. One suggested cause of unexplained gut activity may be secondary to swallowed activity in the saliva from the normal submandibular activity in children.

  11. Developmental Aspects of Reaction to Positive Inducements

    ERIC Educational Resources Information Center

    Lindskold, Svenn; And Others

    1970-01-01

    Probes children's behavioral sensitivity to variation in reward probability and magnitude (bribes) and suggests that preadolescent children do respond to promises of positive inducements for cooperation in a mixed-motive situation. (WY)

  12. False positive rates in Voxel-based Morphometry studies of the human brain: should we be worried?

    PubMed

    Scarpazza, Cristina; Tognin, Stefania; Frisciata, Silvia; Sartori, Giuseppe; Mechelli, Andrea

    2015-05-01

    Voxel-based Morphometry (VBM) is a widely used automated technique for the analysis of neuroanatomical images. Despite its popularity within the neuroimaging community, there are outstanding concerns about its potential susceptibility to false positive findings. Here we review the main methodological factors that are known to influence the results of VBM studies comparing two groups of subjects. We then use two large, open-access data sets to empirically estimate false positive rates and how these depend on sample size, degree of smoothing and modulation. Our review and investigation provide three main results: (i) when groups of equal size are compared false positive rate is not higher than expected, i.e. about 5%; (ii) the sample size, degree of smoothing and modulation do not appear to influence false positive rate; (iii) when they exist, false positive findings are randomly distributed across the brain. These results provide reassurance that VBM studies comparing groups are not vulnerable to the higher than expected false positive rates that are evident in single case VBM.

  13. Positive Psychology and Adolescent Mental Health: False Promise or True Breakthrough?

    ERIC Educational Resources Information Center

    Kelley, Thomas M.

    2004-01-01

    The emerging field of positive psychology has pledged to improve the mental health of American adolescents. Yet, without a principle-based conceptual foundation to guide its study of optimal youth functioning, positive psychology will ultimately fail to keep its promise. This paper suggests that the principles of Mind, Thought and Consciousness…

  14. Efavirenz does not cause false-positive urine cannabis test in HIV-infected patients on Highly Active Anti-Retroviral Therapy.

    PubMed

    Koh, K C; Lee, W Y; Eh, Z W; Nor Julaika, I; Tee, P S; Azizon, O; Thilageswary, M

    2013-06-01

    Efavirenz is a non-nucleoside reverse transcriptase inhibitor used in combination with other drugs for the treatment of patients with HIV infection. Efavirenz has been reported to cause a positive urine cannabis test reaction which may create problems between HIV-infected patients on Efavirenz and law enforcement agencies. Doctors are at loss whether to issue documents certifying the potential false positive urine cannabis test with Efavirenz to patients. We investigated if the urine of HIV-infected patients on Efavirenz caused a positive urine cannabis test using the AxSYM Cannabinoids Assay®. Urine samples from 51 eligible patients on Efavirenz were tested for cannabis. All tested negative except for one who had used cannabis the day before. Efavirenz does not cause false positive urine cannabis test with the AxSYM Cannabinoids Assay®. Certification documents from doctors are therefore unnecessary.

  15. False positive dengue NS1 antigen test in a traveller with an acute Zika virus infection imported into Switzerland.

    PubMed

    Gyurech, Danielle; Schilling, Julian; Schmidt-Chanasit, Jonas; Cassinotti, Pascal; Kaeppeli, Franz; Dobec, Marinko

    2016-01-01

    We report the first case of an acute Zika virus infection imported into Switzerland by a traveller returning from Canoa Quebrada, Ceará state, in the north-eastern part of Brazil. Due to a false positive dengue virus NS1 antigen test, IgG antibody seroconversion and a suggestive clinical picture,an acute dengue fever was initially considered. However, because of lack of specific IgM-antibodies, stationary IgG antibody titre and a negative dengue virus PCR test result, a dengue virus infection was excluded and a cross-reaction with other, causative flaviviruses was postulated. Based on recent reports of Zika fever cases in the north-eastern parts of Brazil, an acute Zika virus infection was suspected. Because of a lack of commercially available Zika virus diagnostic tests, the case was confirmed in the WHO reference laboratory. As the clinical presentation of Zika virus infection can be confused with dengue fever and chikungunya fever, and because of possible public health implications, all patients returning from affected areas should be additionally tested for Zika virus. This case illustrates the urgent medical need for a broadly available assay capable of differentiating Zika from Dengue infections.

  16. All That Glisters Is Not Gold: Sampling-Process Uncertainty in Disease-Vector Surveys with False-Negative and False-Positive Detections

    PubMed Central

    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

  17. Cross-reactivity between Lyme and syphilis screening assays: Lyme disease does not cause false-positive syphilis screens.

    PubMed

    Patriquin, Glenn; LeBlanc, Jason; Heinstein, Charles; Roberts, Catherine; Lindsay, Robbin; Hatchette, Todd F

    2016-03-01

    Increased rates of Lyme disease and syphilis in the same geographic area prompted an assessment of screening test cross-reactivity. This study supports the previously described cross-reactivity of Lyme screening among syphilis-positive sera and reports evidence against the possibility of false-positive syphilis screening tests resulting from previous Borrelia burgdorferi infection.

  18. False-positive radionuclide hepatobiliary imaging following cystic duct stone removal

    SciTech Connect

    Zagoria, R.J.; Cowan, R.J.; Dyer, R.B.; Herrera, M.

    1989-03-01

    The authors report a case in which a radionuclide hepatobiliary image was falsely indicative of cystic duct obstruction in a patient with an indwelling cholecystostomy tube and an externalized gallbladder-duodenal stent. Cystic duct patency was demonstrated radiographically shortly before and after the radionuclide study. The authors recommend that cystic duct obstruction indicated by a radionuclide hepatobiliary image be confirmed by another means if a cholecystostomy tube is present, or if the patient recently has undergone percutaneous gallbladder or cystic duct manipulations.

  19. [False-positive results obtained on examining slaughtered animals for the presence of antibiotic residues (author's transl)].

    PubMed

    Nouws, J F

    1975-06-15

    As part of the examination of emergency-slaughtered animals for the presence of antibiotic residues, studies were done to see whether false-positive results would be obtained when the Sarcina lutea kidney test and Bacillus subtilis BGA test were performed. When the S. lutea kidney test was positive in cattle, calves and swine, penicillin was invariably found to be present in those animals, the histories of which showed that they had not been given antibiotics. A syringe and an injected fluid containing penicillin residues are regarded as possible causes of these positive results. When the S. lutea kidney test was performed in horses which had been in a state of stress prior to slaughter, false-positive results were occasionally observed. When the German B. subtilis BGA test was used, a large number of false-positive results were recorded, among others in equine kidneys. This shows that the use of this test in examining the kidney is a highly controversial matter. A number of drugs used in veterinary medicine may have an inhibitory effect on the growth of S. lutea and B. subtilis BGA test organisms in vitro. When these drugs were used therapeutically (in vivo), the result of the S. lutea kidney test was not positive in any of the cases studied. On the other hand, false-positive results were obtained when the B. subtilis BGA renal medullary test was performed in those animals in which lidocaine and calcium borogluconate had also been injected.

  20. False Positive B-Cells Crossmatch after Prior Rituximab Exposure of the Kidney Donor

    PubMed Central

    Desoutter, Judith; Apithy, Marie-Joëlle; Bartczak, Ségolène; Guillaume, Nicolas

    2016-01-01

    Crossmatching is essential prior to kidney transplantation to confirm compatibility between the donor and the recipient, particularly to prevent acute antibody-mediated rejection. An unexpected positive crossmatch may be obtained in recipients with an autoimmune disease or preexisting antibodies not detected by single-antigen bead array due to complement interference or who have been previously treated by desensitization protocols such as rituximab, antithymocyte globulin, or intravenous immunoglobulins. We report donor and recipient investigations that revealed unexpected positive B-cells crossmatch, probably due to donor cells, as the donor had received rituximab therapy shortly before organ harvesting, in a context of severe idiopathic thrombocytopenic purpura. We consequently detected unexpected Class II IgG complement-dependent cytotoxicity for all sera tested. Other laboratory investigations failed to elucidate the reasons for this recipient-related positivity. PMID:27239362

  1. Efficient information theoretic strategies for classifier combination, feature extraction and performance evaluation in improving false positives and false negatives for spam e-mail filtering.

    PubMed

    Zorkadis, V; Karras, D A; Panayotou, M

    2005-01-01

    Spam emails are considered as a serious privacy-related violation, besides being a costly, unsolicited communication. Various spam filtering techniques have been so far proposed, mainly based on Naïve Bayesian algorithms. Other Machine Learning algorithms like Boosting trees, or Support Vector Machines (SVM) have already been used with success. However, the number of False Positives (FP) and False Negatives (FN) resulting through applying various spam e-mail filters still remains too high and the problem of spam e-mail categorization cannot be solved completely from a practical viewpoint. In this paper, we propose a novel approach for spam e-mail filtering based on efficient information theoretic techniques for integrating classifiers, for extracting improved features and for properly evaluating categorization accuracy in terms of FP and FN. The goal of the presented methodology is to empirically but explicitly minimize these FP and FN numbers by combining high-performance FP filters with high-performance FN filters emerging from a previous work of the authors [Zorkadis, V., Panayotou, M., & Karras, D. A. (2005). Improved spam e-mail filtering based on committee machines and information theoretic feature extraction. Proceedings of the International Joint Conference on Neural Networks, July 31-August 4, 2005, Montreal, Canada]. To this end, Random Committee-based filters along with ADTree-based ones are efficiently combined through information theory, respectively. The experiments conducted are of the most extensive ones so far in the literature, exploiting widely accepted benchmarking e-mail data sets and comparing the proposed methodology with the Naive Bayes spam filter as well as with the Boosting tree methodology, the classification via regression and other machine learning models. It is illustrated by means of novel information theoretic measures of FP & FN filtering performance that the proposed approach is very favorably compared to the other rival methods

  2. False-positive rate determination of protein target discovery using a covalent modification- and mass spectrometry-based proteomics platform.

    PubMed

    Strickland, Erin C; Geer, M Ariel; Hong, Jiyong; Fitzgerald, Michael C

    2014-01-01

    Detection and quantitation of protein-ligand binding interactions is important in many areas of biological research. Stability of proteins from rates of oxidation (SPROX) is an energetics-based technique for identifying the proteins targets of ligands in complex biological mixtures. Knowing the false-positive rate of protein target discovery in proteome-wide SPROX experiments is important for the correct interpretation of results. Reported here are the results of a control SPROX experiment in which chemical denaturation data is obtained on the proteins in two samples that originated from the same yeast lysate, as would be done in a typical SPROX experiment except that one sample would be spiked with the test ligand. False-positive rates of 1.2-2.2% and <0.8% are calculated for SPROX experiments using Q-TOF and Orbitrap mass spectrometer systems, respectively. Our results indicate that the false-positive rate is largely determined by random errors associated with the mass spectral analysis of the isobaric mass tag (e.g., iTRAQ®) reporter ions used for peptide quantitation. Our results also suggest that technical replicates can be used to effectively eliminate such false positives that result from this random error, as is demonstrated in a SPROX experiment to identify yeast protein targets of the drug, manassantin A. The impact of ion purity in the tandem mass spectral analyses and of background oxidation on the false-positive rate of protein target discovery using SPROX is also discussed.

  3. False-Positive Rate Determination of Protein Target Discovery using a Covalent Modification- and Mass Spectrometry-Based Proteomics Platform

    NASA Astrophysics Data System (ADS)

    Strickland, Erin C.; Geer, M. Ariel; Hong, Jiyong; Fitzgerald, Michael C.

    2014-01-01

    Detection and quantitation of protein-ligand binding interactions is important in many areas of biological research. Stability of proteins from rates of oxidation (SPROX) is an energetics-based technique for identifying the proteins targets of ligands in complex biological mixtures. Knowing the false-positive rate of protein target discovery in proteome-wide SPROX experiments is important for the correct interpretation of results. Reported here are the results of a control SPROX experiment in which chemical denaturation data is obtained on the proteins in two samples that originated from the same yeast lysate, as would be done in a typical SPROX experiment except that one sample would be spiked with the test ligand. False-positive rates of 1.2-2.2 % and <0.8 % are calculated for SPROX experiments using Q-TOF and Orbitrap mass spectrometer systems, respectively. Our results indicate that the false-positive rate is largely determined by random errors associated with the mass spectral analysis of the isobaric mass tag (e.g., iTRAQ®) reporter ions used for peptide quantitation. Our results also suggest that technical replicates can be used to effectively eliminate such false positives that result from this random error, as is demonstrated in a SPROX experiment to identify yeast protein targets of the drug, manassantin A. The impact of ion purity in the tandem mass spectral analyses and of background oxidation on the false-positive rate of protein target discovery using SPROX is also discussed.

  4. Is it time to sound an alarm about false-positive cell-free DNA testing for fetal aneuploidy?

    PubMed

    Mennuti, Michael T; Cherry, Athena M; Morrissette, Jennifer J D; Dugoff, Lorraine

    2013-11-01

    Testing cell-free DNA (cfDNA) in maternal blood samples has been shown to have very high sensitivity for the detection of fetal aneuploidy with very low false-positive results in high-risk patients who undergo invasive prenatal diagnosis. Recent observation in clinical practice of several cases of positive cfDNA tests for trisomy 18 and trisomy 13, which were not confirmed by cytogenetic testing of the pregnancy, may reflect a limitation of the positive predictive value of this quantitative testing, particularly when it is used to detect rare aneuploidies. Analysis of a larger number of false-positive cases is needed to evaluate whether these observations reflect the positive predictive value that should be expected. Infrequently, mechanisms (such as low percentage mosaicism or confined placental mosaicism) might also lead to positive cfDNA testing that is not concordant with standard prenatal cytogenetic diagnosis. The need to explore these and other possible causes of false-positive cfDNA testing is exemplified by 2 of these cases. Additional evaluation of cfDNA testing in clinical practice and a mechanism for the systematic reporting of false-positive and false-negative cases will be important before this test is offered widely to the general population of low-risk obstetric patients. In the meantime, incorporating information about the positive predictive value in pretest counseling and in clinical laboratory reports is recommended. These experiences reinforce the importance of offering invasive testing to confirm cfDNA results before parental decision-making.

  5. Is it time to sound an alarm about false-positive cell-free DNA testing for fetal aneuploidy?

    PubMed

    Mennuti, Michael T; Cherry, Athena M; Morrissette, Jennifer J D; Dugoff, Lorraine

    2013-11-01

    Testing cell-free DNA (cfDNA) in maternal blood samples has been shown to have very high sensitivity for the detection of fetal aneuploidy with very low false-positive results in high-risk patients who undergo invasive prenatal diagnosis. Recent observation in clinical practice of several cases of positive cfDNA tests for trisomy 18 and trisomy 13, which were not confirmed by cytogenetic testing of the pregnancy, may reflect a limitation of the positive predictive value of this quantitative testing, particularly when it is used to detect rare aneuploidies. Analysis of a larger number of false-positive cases is needed to evaluate whether these observations reflect the positive predictive value that should be expected. Infrequently, mechanisms (such as low percentage mosaicism or confined placental mosaicism) might also lead to positive cfDNA testing that is not concordant with standard prenatal cytogenetic diagnosis. The need to explore these and other possible causes of false-positive cfDNA testing is exemplified by 2 of these cases. Additional evaluation of cfDNA testing in clinical practice and a mechanism for the systematic reporting of false-positive and false-negative cases will be important before this test is offered widely to the general population of low-risk obstetric patients. In the meantime, incorporating information about the positive predictive value in pretest counseling and in clinical laboratory reports is recommended. These experiences reinforce the importance of offering invasive testing to confirm cfDNA results before parental decision-making. PMID:23529082

  6. Way forward in case of a false positive in vitro genotoxicity result for a cosmetic substance?

    PubMed

    Doktorova, Tatyana Y; Ates, Gamze; Vinken, Mathieu; Vanhaecke, Tamara; Rogiers, Vera

    2014-02-01

    The currently used regulatory in vitro mutagenicity/genotoxicity test battery has a high sensitivity for detecting genotoxicants, but it suffers from a large number of irrelevant positive results (i.e. low specificity) thereby imposing the need for additional follow-up by in vitro and/or in vivo genotoxicity tests. This could have a major impact on the cosmetic industry in Europe, seen the imposed animal testing and marketing bans on cosmetics and their ingredients. Afflicted, but safe substances could therefore be lost. Using the example of triclosan, a cosmetic preservative, we describe here the potential applicability of a human toxicogenomics-based in vitro assay as a potential mechanistically based follow-up test for positive in vitro genotoxicity results. Triclosan shows a positive in vitro chromosomal aberration test, but is negative during in vivo follow-up tests. Toxicogenomics analysis unequivocally shows that triclosan is identified as a compound acting through non-DNA reactive mechanisms. This proof-of-principle study illustrates the potential of genome-wide transcriptomics data in combination with in vitro experimentation as a possible weight-of-evidence follow-up approach for de-risking a positive outcome in a standard mutagenicity/genotoxicity battery. As such a substantial number of cosmetic compounds wrongly identified as genotoxicants could be saved for the future. PMID:24095862

  7. Way forward in case of a false positive in vitro genotoxicity result for a cosmetic substance?

    PubMed

    Doktorova, Tatyana Y; Ates, Gamze; Vinken, Mathieu; Vanhaecke, Tamara; Rogiers, Vera

    2014-02-01

    The currently used regulatory in vitro mutagenicity/genotoxicity test battery has a high sensitivity for detecting genotoxicants, but it suffers from a large number of irrelevant positive results (i.e. low specificity) thereby imposing the need for additional follow-up by in vitro and/or in vivo genotoxicity tests. This could have a major impact on the cosmetic industry in Europe, seen the imposed animal testing and marketing bans on cosmetics and their ingredients. Afflicted, but safe substances could therefore be lost. Using the example of triclosan, a cosmetic preservative, we describe here the potential applicability of a human toxicogenomics-based in vitro assay as a potential mechanistically based follow-up test for positive in vitro genotoxicity results. Triclosan shows a positive in vitro chromosomal aberration test, but is negative during in vivo follow-up tests. Toxicogenomics analysis unequivocally shows that triclosan is identified as a compound acting through non-DNA reactive mechanisms. This proof-of-principle study illustrates the potential of genome-wide transcriptomics data in combination with in vitro experimentation as a possible weight-of-evidence follow-up approach for de-risking a positive outcome in a standard mutagenicity/genotoxicity battery. As such a substantial number of cosmetic compounds wrongly identified as genotoxicants could be saved for the future.

  8. A False-Positive Detection Bias as a Function of State and Trait Schizotypy in Interaction with Intelligence

    PubMed Central

    Grant, Phillip; Balser, Mona; Munk, Aisha Judith Leila; Linder, Jens; Hennig, Juergen

    2014-01-01

    Hallucinatory experiences are by far not limited to patients with clinical psychosis. A number of internal and external factors may bring about such experiences in healthy individuals, whereby the personality trait of (positive) schizotypy is a major mediator of individual differences. Psychotic experiences are defined as associating abnormal meaning to real but objectively irrelevant perceptions. Especially, the ambiguity of a stimulus correlates positively with the likelihood of abnormal interpretation, and intelligence is believed to have an important influence and act as protective against clinical psychosis in highly schizotypic individuals. In this study, we presented 131 healthy participants with 216 15-letter strings containing either a word, a non-word, or only random letters and asked them to report, whether or not they believed to have seen a word. The aim was to replicate findings that participants with high values in positive schizotypy on the trait-level make more false-positive errors and assess the role of stimulus-ambiguity and verbal intelligence. Additionally, we wanted to examine whether the same effect could be shown for indices of state schizotypy. Our results support findings that both state and trait positive schizotypy explain significant variance in “seeing things that are not there” and that the properties of individual stimuli have additional strong effects on the false-positive hit rates. Finally, we found that verbal intelligence and positive schizotypy interact with stimulus-ambiguity in the production of false-positive perceptions. PMID:25309464

  9. The probability of false positives in zero-dimensional analyses of one-dimensional kinematic, force and EMG trajectories.

    PubMed

    Pataky, Todd C; Vanrenterghem, Jos; Robinson, Mark A

    2016-06-14

    A false positive is the mistake of inferring an effect when none exists, and although α controls the false positive (Type I error) rate in classical hypothesis testing, a given α value is accurate only if the underlying model of randomness appropriately reflects experimentally observed variance. Hypotheses pertaining to one-dimensional (1D) (e.g. time-varying) biomechanical trajectories are most often tested using a traditional zero-dimensional (0D) Gaussian model of randomness, but variance in these datasets is clearly 1D. The purpose of this study was to determine the likelihood that analyzing smooth 1D data with a 0D model of variance will produce false positives. We first used random field theory (RFT) to predict the probability of false positives in 0D analyses. We then validated RFT predictions via numerical simulations of smooth Gaussian 1D trajectories. Results showed that, across a range of public kinematic, force/moment and EMG datasets, the median false positive rate was 0.382 and not the assumed α=0.05, even for a simple two-sample t test involving N=10 trajectories per group. The median false positive rate for experiments involving three-component vector trajectories was p=0.764. This rate increased to p=0.945 for two three-component vector trajectories, and to p=0.999 for six three-component vectors. This implies that experiments involving vector trajectories have a high probability of yielding 0D statistical significance when there is, in fact, no 1D effect. Either (a) explicit a priori identification of 0D variables or (b) adoption of 1D methods can more tightly control α. PMID:27067363

  10. False-positive findings in Cochrane meta-analyses with and without application of trial sequential analysis: an empirical review

    PubMed Central

    Imberger, Georgina; Thorlund, Kristian; Gluud, Christian; Wetterslev, Jørn

    2016-01-01

    Objective Many published meta-analyses are underpowered. We explored the role of trial sequential analysis (TSA) in assessing the reliability of conclusions in underpowered meta-analyses. Methods We screened The Cochrane Database of Systematic Reviews and selected 100 meta-analyses with a binary outcome, a negative result and sufficient power. We defined a negative result as one where the 95% CI for the effect included 1.00, a positive result as one where the 95% CI did not include 1.00, and sufficient power as the required information size for 80% power, 5% type 1 error, relative risk reduction of 10% or number needed to treat of 100, and control event proportion and heterogeneity taken from the included studies. We re-conducted the meta-analyses, using conventional cumulative techniques, to measure how many false positives would have occurred if these meta-analyses had been updated after each new trial. For each false positive, we performed TSA, using three different approaches. Results We screened 4736 systematic reviews to find 100 meta-analyses that fulfilled our inclusion criteria. Using conventional cumulative meta-analysis, false positives were present in seven of the meta-analyses (7%, 95% CI 3% to 14%), occurring more than once in three. The total number of false positives was 14 and TSA prevented 13 of these (93%, 95% CI 68% to 98%). In a post hoc analysis, we found that Cochrane meta-analyses that are negative are 1.67 times more likely to be updated (95% CI 0.92 to 2.68) than those that are positive. Conclusions We found false positives in 7% (95% CI 3% to 14%) of the included meta-analyses. Owing to limitations of external validity and to the decreased likelihood of updating positive meta-analyses, the true proportion of false positives in meta-analysis is probably higher. TSA prevented 93% of the false positives (95% CI 68% to 98%). PMID:27519923

  11. False-Positive Serum Botulism Bioassay in Miller-Fisher Syndrome.

    PubMed

    Zeylikman, Yuriy; Shah, Vishal; Shah, Umang; Mirsen, Thomas R; Campellone, Joseph V

    2015-09-01

    We describe a patient with acute progressive weakness and areflexia. Both botulism and Miller-Fisher variant of Guillain-Barré syndrome were initial diagnostic considerations, and she was treated with intravenous immunoglobulin and botulinum antitoxin. A mouse bioassay was positive for botulinum toxin A, although her clinical course, electrodiagnostic studies, and cerebrospinal fluid findings supported Miller-Fisher syndrome. This patient's atypical features offer points of discussion regarding the evaluation of patients with acute neuromuscular weakness and emphasize the limitations of the botulism bioassay.

  12. False-Positive Serum Botulism Bioassay in Miller-Fisher Syndrome.

    PubMed

    Zeylikman, Yuriy; Shah, Vishal; Shah, Umang; Mirsen, Thomas R; Campellone, Joseph V

    2015-09-01

    We describe a patient with acute progressive weakness and areflexia. Both botulism and Miller-Fisher variant of Guillain-Barré syndrome were initial diagnostic considerations, and she was treated with intravenous immunoglobulin and botulinum antitoxin. A mouse bioassay was positive for botulinum toxin A, although her clinical course, electrodiagnostic studies, and cerebrospinal fluid findings supported Miller-Fisher syndrome. This patient's atypical features offer points of discussion regarding the evaluation of patients with acute neuromuscular weakness and emphasize the limitations of the botulism bioassay. PMID:26301377

  13. Doctor can't make lab pay damages for false-positive HIV test.

    PubMed

    1997-08-22

    The Texas Court of Appeals ruled that physician [name removed] was not eligible for damages from a laboratory that misreported HIV test results for one of her patients. [Name removed] sued Pathlab, Inc., a laboratory that had a policy of performing an ELISA test and a Western blot test, but that only reported the ELISA result unless a physician specifically requested and paid for the Western blot results. One of Dr. [name removed]'s patients was diagnosed as HIV-positive in error; the patient sued [name removed] and Pathlab. All claims against Dr. [name removed] were dismissed. The court ruled that Dr. [name removed] could not seek damages against Pathlab because this would have amounted to an improper attempt to gain indemnification.

  14. Patients' & Healthcare Professionals' Values Regarding True- & False-Positive Diagnosis when Colorectal Cancer Screening by CT Colonography: Discrete Choice Experiment

    PubMed Central

    Boone, Darren; Mallett, Susan; Zhu, Shihua; Yao, Guiqing Lily; Bell, Nichola; Ghanouni, Alex; von Wagner, Christian; Taylor, Stuart A.; Altman, Douglas G.; Lilford, Richard; Halligan, Steve

    2013-01-01

    Purpose To establish the relative weighting given by patients and healthcare professionals to gains in diagnostic sensitivity versus loss of specificity when using CT colonography (CTC) for colorectal cancer screening. Materials and Methods Following ethical approval and informed consent, 75 patients and 50 healthcare professionals undertook a discrete choice experiment in which they chose between “standard” CTC and “enhanced” CTC that raised diagnostic sensitivity 10% for either cancer or polyps in exchange for varying levels of specificity. We established the relative increase in false-positive diagnoses participants traded for an increase in true-positive diagnoses. Results Data from 122 participants were analysed. There were 30 (25%) non-traders for the cancer scenario and 20 (16%) for the polyp scenario. For cancer, the 10% gain in sensitivity was traded up to a median 45% (IQR 25 to >85) drop in specificity, equating to 2250 (IQR 1250 to >4250) additional false-positives per additional true-positive cancer, at 0.2% prevalence. For polyps, the figure was 15% (IQR 7.5 to 55), equating to 6 (IQR 3 to 22) additional false-positives per additional true-positive polyp, at 25% prevalence. Tipping points were significantly higher for patients than professionals for both cancer (85 vs 25, p<0.001) and polyps (55 vs 15, p<0.001). Patients were willing to pay significantly more for increased sensitivity for cancer (p = 0.021). Conclusion When screening for colorectal cancer, patients and professionals believe gains in true-positive diagnoses are worth much more than the negative consequences of a corresponding rise in false-positives. Evaluation of screening tests should account for this. PMID:24349014

  15. False-positive results in ELISA-based anti FVIII antibody assay may occur with lupus anticoagulant and phospholipid antibodies.

    PubMed

    Sahud, M; Zhukov, O; Mo, K; Popov, J; Dlott, J

    2012-09-01

    The evaluation of a prolonged aPTT often includes Lupus Anticoagulant, Antiphospholipid Antibodies, and Factor VIII (FVIII) inhibitors. We have noticed that patient samples positive for lupus antibody (LA) are frequently also positive for FVIII IgG antibodies in an enzyme-linked immunosorbent assay (ELISA), indicating the need for follow-up testing with a more labour-intensive functional assay for FVIII inhibition. This study evaluates the potential for a FVIII IgG ELISA to yield false-positive results in patient samples positive for LA or other antiphospholipid antibodies. A total of 289 residual de-identified patient samples positive for LA (n = 143), anti-cardiolipin IgG (n = 84), or beta2-glycoprotein antibody (n = 62) were tested for FVIII IgG using a commercial ELISA. Samples with positive FVIII IgG ELISA results were further tested for FVIII activity using a clot-based FVIII inhibitor assay. The FVIII IgG ELISA yielded positive results in 39 (13%) of the samples tested, including 13/143 (13%) LA-positive, 15/85 (18%) aCL IgG-positive and 6/62 (10%) β2-glycoprotein IgG-positive samples. The clot-based FVIII inhibitor assay yielded negative results in all 39 FVIII IgG-positive specimens tested, indicating discrepancy with the FVIII IgG ELISA results. Patient specimens positive for LA, aCL IgG, or β2-glycoprotein IgG may yield false-positive results for FVIII antibodies. Caution is warranted in interpreting FVIII antibody results in these cases.

  16. The evaluation of possible false positives with detergents when performing amylase serological testing on clothing.

    PubMed

    Feia, Andrea; Novroski, Nicole

    2013-01-01

    For almost 40 years, detergent companies have been adding enzymes such as amylases to their products as an effective method of breaking down tough stains created by polysaccharides and proteins. The possibility that α-amylases present in common household laundry detergents may contribute to the positive detection of α-amylase on evidentiary samples during forensic presumptive screening procedures is a potential problem that has not yet been investigated. To determine whether α-amylase detection is possible following routine laundering, five different fabrics were laundered in a variety of detergents, and presumptive testing using RSID(™)-Saliva and Phadebas(®) Amylase Test was conducted. Our results demonstrate that clothing laundered in detergents known to contain enzymes does not retain any detectable levels of α-amylase following a typical wash cycle. We also show that, unlike laundered clothing, undiluted detergents do contain detectable levels of α-amylase; however, these findings were only observed using the Phadebas(®) Amylase Test.

  17. Distinguishing binders from false positives by free energy calculations: fragment screening against the flap site of HIV protease.

    PubMed

    Deng, Nanjie; Forli, Stefano; He, Peng; Perryman, Alex; Wickstrom, Lauren; Vijayan, R S K; Tiefenbrunn, Theresa; Stout, David; Gallicchio, Emilio; Olson, Arthur J; Levy, Ronald M

    2015-01-22

    Molecular docking is a powerful tool used in drug discovery and structural biology for predicting the structures of ligand-receptor complexes. However, the accuracy of docking calculations can be limited by factors such as the neglect of protein reorganization in the scoring function; as a result, ligand screening can produce a high rate of false positive hits. Although absolute binding free energy methods still have difficulty in accurately rank-ordering binders, we believe that they can be fruitfully employed to distinguish binders from nonbinders and reduce the false positive rate. Here we study a set of ligands that dock favorably to a newly discovered, potentially allosteric site on the flap of HIV-1 protease. Fragment binding to this site stabilizes a closed form of protease, which could be exploited for the design of allosteric inhibitors. Twenty-three top-ranked protein-ligand complexes from AutoDock were subject to the free energy screening using two methods, the recently developed binding energy analysis method (BEDAM) and the standard double decoupling method (DDM). Free energy calculations correctly identified most of the false positives (≥83%) and recovered all the confirmed binders. The results show a gap averaging ≥3.7 kcal/mol, separating the binders and the false positives. We present a formula that decomposes the binding free energy into contributions from the receptor conformational macrostates, which provides insights into the roles of different binding modes. Our binding free energy component analysis further suggests that improving the treatment for the desolvation penalty associated with the unfulfilled polar groups could reduce the rate of false positive hits in docking. The current study demonstrates that the combination of docking with free energy methods can be very useful for more accurate ligand screening against valuable drug targets.

  18. Endogenous biotin-binding proteins: an overlooked factor causing false positives in streptavidin-based protein detection

    PubMed Central

    Tytgat, Hanne L P; Schoofs, Geert; Driesen, Michèle; Proost, Paul; Van Damme, Els J M; Vanderleyden, Jos; Lebeer, Sarah

    2015-01-01

    Biotinylation is widely used in DNA, RNA and protein probing assays as this molecule has generally no impact on the biological activity of its substrate. During the streptavidin-based detection of glycoproteins in Lactobacillus rhamnosus GG with biotinylated lectin probes, a strong positive band of approximately 125 kDa was observed, present in different cellular fractions. This potential glycoprotein reacted heavily with concanavalin A (ConA), a lectin that specifically binds glucose and mannose residues. Surprisingly, this protein of 125 kDa could not be purified using a ConA affinity column. Edman degradation of the protein, isolated via cation and anion exchange chromatography, lead to the identification of the band as pyruvate carboxylase, an enzyme of 125 kDa that binds biotin as a cofactor. Detection using only the streptavidin conjugate resulted in more false positive signals of proteins, also in extracellular fractions, indicating biotin-associated proteins. Indeed, biotin is a known cofactor of numerous carboxylases. The potential occurence of false positive bands with biotinylated protein probes should thus be considered when using streptavidin-based detection, e.g. by developing a blot using only the streptavidin conjugate. To circumvent these false positives, alternative approaches like detection based on digoxigenin labelling can also be used. PMID:25211245

  19. Identification of false positive exercise tests with use of electrocardiographic criteria: A possible role for atrial repolarization waves

    SciTech Connect

    Sapin, P.M.; Koch, G.; Blauwet, M.B.; McCarthy, J.J.; Hinds, S.W.; Gettes, L.S. )

    1991-07-01

    Atrial repolarization waves are opposite in direction to P waves, may have a magnitude of 100 to 200 mu V and may extend into the ST segment and T wave. It was postulated that exaggerated atrial repolarization waves during exercise could produce ST segment depression mimicking myocardial ischemia. The P waves, PR segments and ST segments were studied in leads II, III, aVF and V4 to V6 in 69 patients whose exercise electrocardiogram (ECG) suggested ischemia (100 mu V horizontal or 150 mu V upsloping ST depression 80 ms after the J point). All had a normal ECG at rest. The exercise test in 25 patients (52% male, mean age 53 years) was deemed false positive because of normal coronary arteriograms and left ventricular function (5 patients) or normal stress single photon emission computed tomographic thallium or gated blood pool scans (16 patients), or both (4 patients). Forty-four patients with a similar age and gender distribution, anginal chest pain and at least one coronary stenosis greater than or equal to 80% served as a true positive control group. The false positive group was characterized by (1) markedly downsloping PR segments at peak exercise, (2) longer exercise time and more rapid peak exercise heart rate than those of the true positive group, and (3) absence of exercise-induced chest pain. The false positive group also displayed significantly greater absolute P wave amplitudes at peak exercise and greater augmentation of P wave amplitude by exercise in all six ECG leads than were observed in the true positive group.

  20. Application of computer-extracted breast tissue texture features in predicting false-positive recalls from screening mammography

    NASA Astrophysics Data System (ADS)

    Ray, Shonket; Choi, Jae Y.; Keller, Brad M.; Chen, Jinbo; Conant, Emily F.; Kontos, Despina

    2014-03-01

    Mammographic texture features have been shown to have value in breast cancer risk assessment. Previous models have also been developed that use computer-extracted mammographic features of breast tissue complexity to predict the risk of false-positive (FP) recall from breast cancer screening with digital mammography. This work details a novel locallyadaptive parenchymal texture analysis algorithm that identifies and extracts mammographic features of local parenchymal tissue complexity potentially relevant for false-positive biopsy prediction. This algorithm has two important aspects: (1) the adaptive nature of automatically determining an optimal number of region-of-interests (ROIs) in the image and each ROI's corresponding size based on the parenchymal tissue distribution over the whole breast region and (2) characterizing both the local and global mammographic appearances of the parenchymal tissue that could provide more discriminative information for FP biopsy risk prediction. Preliminary results show that this locallyadaptive texture analysis algorithm, in conjunction with logistic regression, can predict the likelihood of false-positive biopsy with an ROC performance value of AUC=0.92 (p<0.001) with a 95% confidence interval [0.77, 0.94]. Significant texture feature predictors (p<0.05) included contrast, sum variance and difference average. Sensitivity for false-positives was 51% at the 100% cancer detection operating point. Although preliminary, clinical implications of using prediction models incorporating these texture features may include the future development of better tools and guidelines regarding personalized breast cancer screening recommendations. Further studies are warranted to prospectively validate our findings in larger screening populations and evaluate their clinical utility.

  1. Do positive nickel reactions increase nonspecific patch test reactivity?

    PubMed

    Lammintausta, K; Kalimo, K

    1987-03-01

    The patch test reaction pattern in nickel-positive and -negative female patients was compared. Cobalt allergy was found in 24.8% of the positive patients. However, the occurrence of allergy to other common agents, i.e., neomycin, perfume mix, balsam of Peru and bacitracin, did not differ significantly between the 2 groups. Even in patients allergic to nickel and cobalt simultaneously, the frequencies were comparable. Chromate and PPDA allergy was significantly commoner in nickel sensitive patients (p less than 0.05 and p less than 0.01). Erythematous or follicular reactions were seen most often to wood tars, propylene glycol, formaldehyde, cobalt, chromate and perfume mix. Reactions to propylene glycol and perfume mix were as frequent in both groups, whereas formaldehyde, cobalt and chromate caused reactions more often in nickel-positive patients (p less than 0.05) and wood tars in negatives (p less than 0.05). Follicular reactions developed especially in patients who were positive to nickel and cobalt. The total number of non-specific reactions was not overpresented in nickel sensitive patients, despite their multiple patch test reactivity.

  2. One Hundred False-Positive Amphetamine Specimens Characterized by Liquid Chromatography Time-of-Flight Mass Spectrometry.

    PubMed

    Marin, Stephanie J; Doyle, Kelly; Chang, Annie; Concheiro-Guisan, Marta; Huestis, Marilyn A; Johnson-Davis, Kamisha L

    2016-01-01

    Some amphetamine (AMP) and ecstacy (MDMA) urine immunoassay (IA) kits are prone to false-positive results due to poor specificity of the antibody. We employed two techniques, high-resolution mass spectrometry (HRMS) and an in silico structure search, to identify compounds likely to cause false-positive results. Hundred false-positive IA specimens for AMP and/or MDMA were analyzed by an Agilent 6230 time-of-flight (TOF) mass spectrometer. Separately, SciFinder (Chemical Abstracts) was used as an in silico structure search to generate a library of compounds that are known to cross-react with AMP/MDMA IAs. Chemical formulas and exact masses of 145 structures were then compared against masses identified by TOF. Compounds known to have cross-reactivity with the IAs were identified in the structure-based search. The chemical formulas and exact masses of 145 structures (of 20 chemical formulas) were compared against masses identified by TOF. Urine analysis by HRMS correlates accurate mass with chemical formulae, but provides little information regarding compound structure. Structural data of targeted antigens can be utilized to correlate HRMS-derived chemical formulas with structural analogs. PMID:26342055

  3. One Hundred False-Positive Amphetamine Specimens Characterized by Liquid Chromatography Time-of-Flight Mass Spectrometry.

    PubMed

    Marin, Stephanie J; Doyle, Kelly; Chang, Annie; Concheiro-Guisan, Marta; Huestis, Marilyn A; Johnson-Davis, Kamisha L

    2016-01-01

    Some amphetamine (AMP) and ecstacy (MDMA) urine immunoassay (IA) kits are prone to false-positive results due to poor specificity of the antibody. We employed two techniques, high-resolution mass spectrometry (HRMS) and an in silico structure search, to identify compounds likely to cause false-positive results. Hundred false-positive IA specimens for AMP and/or MDMA were analyzed by an Agilent 6230 time-of-flight (TOF) mass spectrometer. Separately, SciFinder (Chemical Abstracts) was used as an in silico structure search to generate a library of compounds that are known to cross-react with AMP/MDMA IAs. Chemical formulas and exact masses of 145 structures were then compared against masses identified by TOF. Compounds known to have cross-reactivity with the IAs were identified in the structure-based search. The chemical formulas and exact masses of 145 structures (of 20 chemical formulas) were compared against masses identified by TOF. Urine analysis by HRMS correlates accurate mass with chemical formulae, but provides little information regarding compound structure. Structural data of targeted antigens can be utilized to correlate HRMS-derived chemical formulas with structural analogs.

  4. On the sample size requirement in genetic association tests when the proportion of false positives is controlled.

    PubMed

    Zou, Guohua; Zuo, Yijun

    2006-01-01

    With respect to the multiple-tests problem, recently an increasing amount of attention has been paid to control the false discovery rate (FDR), the positive false discovery rate (pFDR), and the proportion of false positives (PFP). The new approaches are generally believed to be more powerful than the classical Bonferroni one. This article focuses on the PFP approach. It demonstrates via examples in genetic association studies that the Bonferroni procedure can be more powerful than the PFP-control one and also shows the intrinsic connection between controlling the PFP and controlling the overall type I error rate. Since controlling the PFP does not necessarily lead to a desired power level, this article addresses the design issue and recommends the sample sizes that can attain the desired power levels when the PFP is controlled. The results in this article also provide rough guidance for the sample sizes to achieve the desired power levels when the FDR and especially the pFDR are controlled.

  5. Dual Position Sensitive MWPC for tracking reaction products at VAMOS++

    NASA Astrophysics Data System (ADS)

    Vandebrouck, M.; Lemasson, A.; Rejmund, M.; Fremont, G.; Pancin, J.; Navin, A.; Michelagnoli, C.; Goupil, J.; Spitaels, C.; Jacquot, B.

    2016-03-01

    The characteristics and performance of a Dual Position Sensitive Multi-Wire Proportional Counter (DPS-MWPC) used to measure the scattering angle, the interaction position on the target and the velocity of reaction products detected in the VAMOS++ magnetic spectrometer, are reported. The detector consists of a pair of position sensitive low pressure MWPCs and provides both fast timing signals, along with the two-dimensional position coordinates required to define the trajectory of the reaction products. A time-of-flight resolution of 305(11) ps (FWHM) was measured. The measured resolutions (FWHM) were 2.5(3) mrad and 560(70) μm for the scattering angle and the interaction point at the target respectively. The subsequent improvement of the Doppler correction of the energy of the γ-rays, detected in the γ-ray tracking array AGATA in coincidence with isotopically identified ions in VAMOS++, is also discussed.

  6. Multi-scale textural feature extraction and particle swarm optimization based model selection for false positive reduction in mammography.

    PubMed

    Zyout, Imad; Czajkowska, Joanna; Grzegorzek, Marcin

    2015-12-01

    The high number of false positives and the resulting number of avoidable breast biopsies are the major problems faced by current mammography Computer Aided Detection (CAD) systems. False positive reduction is not only a requirement for mass but also for calcification CAD systems which are currently deployed for clinical use. This paper tackles two problems related to reducing the number of false positives in the detection of all lesions and masses, respectively. Firstly, textural patterns of breast tissue have been analyzed using several multi-scale textural descriptors based on wavelet and gray level co-occurrence matrix. The second problem addressed in this paper is the parameter selection and performance optimization. For this, we adopt a model selection procedure based on Particle Swarm Optimization (PSO) for selecting the most discriminative textural features and for strengthening the generalization capacity of the supervised learning stage based on a Support Vector Machine (SVM) classifier. For evaluating the proposed methods, two sets of suspicious mammogram regions have been used. The first one, obtained from Digital Database for Screening Mammography (DDSM), contains 1494 regions (1000 normal and 494 abnormal samples). The second set of suspicious regions was obtained from database of Mammographic Image Analysis Society (mini-MIAS) and contains 315 (207 normal and 108 abnormal) samples. Results from both datasets demonstrate the efficiency of using PSO based model selection for optimizing both classifier hyper-parameters and parameters, respectively. Furthermore, the obtained results indicate the promising performance of the proposed textural features and more specifically, those based on co-occurrence matrix of wavelet image representation technique. PMID:25795630

  7. Multi-scale textural feature extraction and particle swarm optimization based model selection for false positive reduction in mammography.

    PubMed

    Zyout, Imad; Czajkowska, Joanna; Grzegorzek, Marcin

    2015-12-01

    The high number of false positives and the resulting number of avoidable breast biopsies are the major problems faced by current mammography Computer Aided Detection (CAD) systems. False positive reduction is not only a requirement for mass but also for calcification CAD systems which are currently deployed for clinical use. This paper tackles two problems related to reducing the number of false positives in the detection of all lesions and masses, respectively. Firstly, textural patterns of breast tissue have been analyzed using several multi-scale textural descriptors based on wavelet and gray level co-occurrence matrix. The second problem addressed in this paper is the parameter selection and performance optimization. For this, we adopt a model selection procedure based on Particle Swarm Optimization (PSO) for selecting the most discriminative textural features and for strengthening the generalization capacity of the supervised learning stage based on a Support Vector Machine (SVM) classifier. For evaluating the proposed methods, two sets of suspicious mammogram regions have been used. The first one, obtained from Digital Database for Screening Mammography (DDSM), contains 1494 regions (1000 normal and 494 abnormal samples). The second set of suspicious regions was obtained from database of Mammographic Image Analysis Society (mini-MIAS) and contains 315 (207 normal and 108 abnormal) samples. Results from both datasets demonstrate the efficiency of using PSO based model selection for optimizing both classifier hyper-parameters and parameters, respectively. Furthermore, the obtained results indicate the promising performance of the proposed textural features and more specifically, those based on co-occurrence matrix of wavelet image representation technique.

  8. Improving screening recall services for women with false-positive mammograms: a comparison of qualitative evidence with UK guidelines

    PubMed Central

    Bond, Mary; Garside, Ruth; Hyde, Christopher

    2015-01-01

    Objectives To gain an understanding of the views of women with false-positive screening mammograms of screening recall services, their ideas for service improvements and how these compare with current UK guidelines. Methods Inductive qualitative content analysis of semistructured interviews of 21 women who had false-positive screening mammograms. These were then compared with UK National Health Service (NHS) guidelines. Results Participants’ concerns about mammography screening recall services focused on issues of communication and choice. Many of the issues raised indicated that the 1998 NHS Breast Screening Programme guidelines on improving the quality of written information sent to women who are recalled, had not been fully implemented. This included being told a clear reason for recall, who may attend with them, the length of appointment, who they will see and what tests will be carried out. Additionally women voiced a need for: reassurance that a swift appointment did not imply they had cancer; choice about invasive assessment or watchful waiting; the offer of a follow-up mammogram for those uncertain about the validity of their all-clear and an extension of the role of the clinical nurse specialist, outlined in the 2012 NHS Breast Screening Programme (NHSBSP) guidelines, to include availability at the clinic after the all-clear for women with false-positive mammograms. Conclusions It is time the NHSBSP 1998 recall information guidelines were fully implemented. Additionally, the further suggestions from this research, including extending the role of the clinical nurses from the 2012 NHSBSP guidelines, should be considered. These actions have the potential to reduce the anxiety of being recalled. PMID:25618139

  9. Experimental evidence of false-positive Comet test results due to TiO2 particle--assay interactions.

    PubMed

    Rajapakse, Katarina; Drobne, Damjana; Kastelec, Damijana; Marinsek-Logar, Romana

    2013-08-01

    We have studied the genotoxicity of TiO2 particles with a Comet assay on a unicellular organism, Tetrahymena thermophila. Exposure to bulk- or nano-TiO2 of free cells, cells embedded in gel or nuclei embedded in gel, all resulted in a positive Comet assay result but this outcome could not be confirmed by cytotoxicity measures such as lipid peroxidation, elevated reactive oxygen species or cell membrane composition. Published reports state that in the absence of cytotoxicity, nano- and bulk-TiO2 genotoxicity do not occur directly, and a possible explanation of our Comet assay results is that they are false positives resulting from post festum exposure interactions between particles and DNA. We suggest that before Comet assay is used for nanoparticle genotoxicity testing, evidence for the possibility of post festum exposure interactions should be considered. The acellular Comet test described in this report can be used for this purpose.

  10. A novel spherical shell filter for reducing false positives in automatic detection of pulmonary nodules in thoracic CT scans

    NASA Astrophysics Data System (ADS)

    van de Leemput, Sil; Dorssers, Frank; Ehteshami Bejnordi, Babak

    2015-03-01

    Early detection of pulmonary nodules is crucial for improving prognosis of patients with lung cancer. Computer-aided detection of lung nodules in thoracic computed tomography (CT) scans has a great potential to enhance the performance of the radiologist in detecting nodules. In this paper we present a computer-aided lung nodule detection system for computed tomography (CT) scans that works in three steps. The system first segments the lung using thresholding and hole filling. From this segmentation the system extracts candidate nodules using Laplacian of Gaussian. To reject false positives among the detected candidate nodules, multiple established features are calculated. We propose a novel feature based on a spherical shell filter, which is specifically designed to distinguish between vascular structures and nodular structures. The performance of the proposed CAD system was evaluated by partaking in the ANODE09 challenge, which presents a platform for comparing automatic nodule detection programs. The results from the challenge show that our CAD system ranks third among the submitted works, demonstrating the efficacy of our proposed CAD system. The results also show that our proposed spherical shell filter in combination with conventional features can significantly reduce the number of false positives from the detected candidate nodules.

  11. Reducing pervasive false-positive identical-by-descent segments detected by large-scale pedigree analysis.

    PubMed

    Durand, Eric Y; Eriksson, Nicholas; McLean, Cory Y

    2014-08-01

    Analysis of genomic segments shared identical-by-descent (IBD) between individuals is fundamental to many genetic applications, from demographic inference to estimating the heritability of diseases, but IBD detection accuracy in nonsimulated data is largely unknown. In principle, it can be evaluated using known pedigrees, as IBD segments are by definition inherited without recombination down a family tree. We extracted 25,432 genotyped European individuals containing 2,952 father-mother-child trios from the 23andMe, Inc. data set. We then used GERMLINE, a widely used IBD detection method, to detect IBD segments within this cohort. Exploiting known familial relationships, we identified a false-positive rate over 67% for 2-4 centiMorgan (cM) segments, in sharp contrast with accuracies reported in simulated data at these sizes. Nearly all false positives arose from the allowance of haplotype switch errors when detecting IBD, a necessity for retrieving long (>6 cM) segments in the presence of imperfect phasing. We introduce HaploScore, a novel, computationally efficient metric that scores IBD segments proportional to the number of switch errors they contain. Applying HaploScore filtering to the IBD data at a precision of 0.8 produced a 13-fold increase in recall when compared with length-based filtering. We replicate the false IBD findings and demonstrate the generalizability of HaploScore to alternative data sources using an independent cohort of 555 European individuals from the 1000 Genomes project. HaploScore can improve the accuracy of segments reported by any IBD detection method, provided that estimates of the genotyping error rate and switch error rate are available. PMID:24784137

  12. Three-dimensional lung nodule segmentation and shape variance analysis to detect lung cancer with reduced false positives.

    PubMed

    Krishnamurthy, Senthilkumar; Narasimhan, Ganesh; Rengasamy, Umamaheswari

    2016-01-01

    The three-dimensional analysis on lung computed tomography scan was carried out in this study to detect the malignant lung nodules. An automatic three-dimensional segmentation algorithm proposed here efficiently segmented the tissue clusters (nodules) inside the lung. However, an automatic morphological region-grow segmentation algorithm that was implemented to segment the well-circumscribed nodules present inside the lung did not segment the juxta-pleural nodule present on the inner surface of wall of the lung. A novel edge bridge and fill technique is proposed in this article to segment the juxta-pleural and pleural-tail nodules accurately. The centroid shift of each candidate nodule was computed. The nodules with more centroid shift in the consecutive slices were eliminated since malignant nodule's resultant position did not usually deviate. The three-dimensional shape variation and edge sharp analyses were performed to reduce the false positives and to classify the malignant nodules. The change in area and equivalent diameter was more for malignant nodules in the consecutive slices and the malignant nodules showed a sharp edge. Segmentation was followed by three-dimensional centroid, shape and edge analysis which was carried out on a lung computed tomography database of 20 patient with 25 malignant nodules. The algorithms proposed in this article precisely detected 22 malignant nodules and failed to detect 3 with a sensitivity of 88%. Furthermore, this algorithm correctly eliminated 216 tissue clusters that were initially segmented as nodules; however, 41 non-malignant tissue clusters were detected as malignant nodules. Therefore, the false positive of this algorithm was 2.05 per patient.

  13. Evidence for false-positive results for boldenone testing of veal urine due to faecal cross-contamination during sampling.

    PubMed

    Sgoifo Rossi, C A; Arioli, F; Bassini, A; Chiesa, L M; Dell'Orto, V; Montana, M; Pompa, G

    2004-08-01

    European Directive 96/22/EC, which controls veterinary residues in animals, does not permit the presence of synthetic growth promoters in products of animal origin or in livestock. Boldenone is categorized in class A3 (growth promoters -- steroids) and is thus a banned substance. Testing of veal urine for banned substances is part of the European Union statutory programme for animals going into the food chain. In relation to this monitoring, three studies were conducted to investigate the apparent presence of the banned growth promoter boldenone in veal urine, which was suspected as being caused by interference from faecal contamination of the sample. In the first study, urine samples were collected at different times (time 0 and after 30 min) using (1) a conventional zoonotechnical apron and (2) a technique designed specifically to avoid faecal contamination ('kettle'). This resulted in samples that were, respectively, positive and negative for the presence of alpha-boldenone (alpha-BOL). In a second study, urine samples negative to alpha-BOL were collected from eight veal calves, but became positive after deliberate faecal contamination. In a third study, data obtained from the Italian RNP (Residual National Program) indicated that 18.1% of 3295 urine samples collected using the zootechnical apron were positive for alpha-BOL and 2.1% for beta-boldenone (beta-BOL), whilst of 902 samples collected using the kettle, beta-BOL was not detected in any samples and only 0.2% were positive to alpha-BOL, in concentrations lower than 2 ng ml(-1). These results further support the supposition that faecal contamination of the urine during sample collection can lead to false-positive results during boldenone analysis.

  14. Experimental Null Method to Guide the Development of Technical Procedures and to Control False-Positive Discovery in Quantitative Proteomics.

    PubMed

    Shen, Xiaomeng; Hu, Qiang; Li, Jun; Wang, Jianmin; Qu, Jun

    2015-10-01

    Comprehensive and accurate evaluation of data quality and false-positive biomarker discovery is critical to direct the method development/optimization for quantitative proteomics, which nonetheless remains challenging largely due to the high complexity and unique features of proteomic data. Here we describe an experimental null (EN) method to address this need. Because the method experimentally measures the null distribution (either technical or biological replicates) using the same proteomic samples, the same procedures and the same batch as the case-vs-contol experiment, it correctly reflects the collective effects of technical variability (e.g., variation/bias in sample preparation, LC-MS analysis, and data processing) and project-specific features (e.g., characteristics of the proteome and biological variation) on the performances of quantitative analysis. To show a proof of concept, we employed the EN method to assess the quantitative accuracy and precision and the ability to quantify subtle ratio changes between groups using different experimental and data-processing approaches and in various cellular and tissue proteomes. It was found that choices of quantitative features, sample size, experimental design, data-processing strategies, and quality of chromatographic separation can profoundly affect quantitative precision and accuracy of label-free quantification. The EN method was also demonstrated as a practical tool to determine the optimal experimental parameters and rational ratio cutoff for reliable protein quantification in specific proteomic experiments, for example, to identify the necessary number of technical/biological replicates per group that affords sufficient power for discovery. Furthermore, we assessed the ability of EN method to estimate levels of false-positives in the discovery of altered proteins, using two concocted sample sets mimicking proteomic profiling using technical and biological replicates, respectively, where the true-positives

  15. Experimental Null Method to Guide the Development of Technical Procedures and to Control False-Positive Discovery in Quantitative Proteomics.

    PubMed

    Shen, Xiaomeng; Hu, Qiang; Li, Jun; Wang, Jianmin; Qu, Jun

    2015-10-01

    Comprehensive and accurate evaluation of data quality and false-positive biomarker discovery is critical to direct the method development/optimization for quantitative proteomics, which nonetheless remains challenging largely due to the high complexity and unique features of proteomic data. Here we describe an experimental null (EN) method to address this need. Because the method experimentally measures the null distribution (either technical or biological replicates) using the same proteomic samples, the same procedures and the same batch as the case-vs-contol experiment, it correctly reflects the collective effects of technical variability (e.g., variation/bias in sample preparation, LC-MS analysis, and data processing) and project-specific features (e.g., characteristics of the proteome and biological variation) on the performances of quantitative analysis. To show a proof of concept, we employed the EN method to assess the quantitative accuracy and precision and the ability to quantify subtle ratio changes between groups using different experimental and data-processing approaches and in various cellular and tissue proteomes. It was found that choices of quantitative features, sample size, experimental design, data-processing strategies, and quality of chromatographic separation can profoundly affect quantitative precision and accuracy of label-free quantification. The EN method was also demonstrated as a practical tool to determine the optimal experimental parameters and rational ratio cutoff for reliable protein quantification in specific proteomic experiments, for example, to identify the necessary number of technical/biological replicates per group that affords sufficient power for discovery. Furthermore, we assessed the ability of EN method to estimate levels of false-positives in the discovery of altered proteins, using two concocted sample sets mimicking proteomic profiling using technical and biological replicates, respectively, where the true-positives

  16. Low False Positive Rate of Kepler Candidates Estimated From A Combination Of Spitzer And Follow-Up Observations

    NASA Astrophysics Data System (ADS)

    Désert, Jean-Michel; Charbonneau, David; Torres, Guillermo; Fressin, François; Ballard, Sarah; Bryson, Stephen T.; Knutson, Heather A.; Batalha, Natalie M.; Borucki, William J.; Brown, Timothy M.; Deming, Drake; Ford, Eric B.; Fortney, Jonathan J.; Gilliland, Ronald L.; Latham, David W.; Seager, Sara

    2015-05-01

    NASA’s Kepler mission has provided several thousand transiting planet candidates during the 4 yr of its nominal mission, yet only a small subset of these candidates have been confirmed as true planets. Therefore, the most fundamental question about these candidates is the fraction of bona fide planets. Estimating the rate of false positives of the overall Kepler sample is necessary to derive the planet occurrence rate. We present the results from two large observational campaigns that were conducted with the Spitzer Space Telescope during the the Kepler mission. These observations are dedicated to estimating the false positive rate (FPR) among the Kepler candidates. We select a sub-sample of 51 candidates, spanning wide ranges in stellar, orbital, and planetary parameter space, and we observe their transits with Spitzer at 4.5 μm. We use these observations to measures the candidate’s transit depths and infrared magnitudes. An authentic planet produces an achromatic transit depth (neglecting the modest effect of limb darkening). Conversely a bandpass-dependent depth alerts us to the potential presence of a blending star that could be the source of the observed eclipse: a false positive scenario. For most of the candidates (85%), the transit depths measured with Kepler are consistent with the transit depths measured with Spitzer as expected for planetary objects, while we find that the most discrepant measurements are due to the presence of unresolved stars that dilute the photometry. The Spitzer constraints on their own yield FPRs between 5% and depending on the Kepler Objects of Interest. By considering the population of the Kepler field stars, and by combining follow-up observations (imaging) when available, we find that the overall FPR of our sample is low. The measured upper limit on the FPR of our sample is 8.8% at a confidence level of 3σ. This observational result, which uses the achromatic property of planetary transit signals that is not investigated

  17. Unusual False-Positive Mesenteric Lymph Nodes Detected by PET/CT in a Metastatic Survey of Lung Cancer.

    PubMed

    Kamiyama, Hirohiko; Sakamoto, Kazuhiro; Niwa, Koichiro; Ishiyama, Shun; Takahashi, Makoto; Kojima, Yutaka; Goto, Michitoshi; Tomiki, Yuichi; Nakamichi, Itsuko; Oh, Shiaki; Suzuki, Kenji

    2016-01-01

    Positron emission tomography/computed tomography (PET/CT) is a credible diagnostic modality for detecting primary and metastatic malignancy. PET/CT sometimes shows false positives and negatives, which make clinical diagnosis difficult. A 42-year-old man who had undergone right upper lobectomy for lung cancer 1 year previously had PET/CT for a metastatic survey of the lung. The lung cancer was stage IB (pT2N0M0) bronchioloalveolar carcinoma. PET/CT showed massive (18)F-fluorodeoxyglucose (FDG) uptake in the mesenteric lymph nodes. Because the mesentery is an unusual site of metastasis, the patient was under watchful observation. Another PET/CT after 6 months still showed FDG uptake in the same location, with a slightly increased standard uptake value. A systemic survey was performed, but it did not reveal any malignancies or inflammatory diseases. Eventually, the patient underwent probing laparoscopic surgery. For complete resection of the lymph nodes, laparoscopic ileocecal resection was performed. Histologically, the resected lymph nodes showed reactive lymphadenitis. Glucose transporter 1 immunostainings of the lung cancer and the lymph node were positive and partially positive, respectively. Although PET/CT is a powerful diagnostic modality, clinical interpretation of unusual results is difficult. PMID:27462197

  18. Unusual False-Positive Mesenteric Lymph Nodes Detected by PET/CT in a Metastatic Survey of Lung Cancer

    PubMed Central

    Kamiyama, Hirohiko; Sakamoto, Kazuhiro; Niwa, Koichiro; Ishiyama, Shun; Takahashi, Makoto; Kojima, Yutaka; Goto, Michitoshi; Tomiki, Yuichi; Nakamichi, Itsuko; Oh, Shiaki; Suzuki, Kenji

    2016-01-01

    Positron emission tomography/computed tomography (PET/CT) is a credible diagnostic modality for detecting primary and metastatic malignancy. PET/CT sometimes shows false positives and negatives, which make clinical diagnosis difficult. A 42-year-old man who had undergone right upper lobectomy for lung cancer 1 year previously had PET/CT for a metastatic survey of the lung. The lung cancer was stage IB (pT2N0M0) bronchioloalveolar carcinoma. PET/CT showed massive 18F-fluorodeoxyglucose (FDG) uptake in the mesenteric lymph nodes. Because the mesentery is an unusual site of metastasis, the patient was under watchful observation. Another PET/CT after 6 months still showed FDG uptake in the same location, with a slightly increased standard uptake value. A systemic survey was performed, but it did not reveal any malignancies or inflammatory diseases. Eventually, the patient underwent probing laparoscopic surgery. For complete resection of the lymph nodes, laparoscopic ileocecal resection was performed. Histologically, the resected lymph nodes showed reactive lymphadenitis. Glucose transporter 1 immunostainings of the lung cancer and the lymph node were positive and partially positive, respectively. Although PET/CT is a powerful diagnostic modality, clinical interpretation of unusual results is difficult. PMID:27462197

  19. Blank-comparison matching-to-sample reveals a false positive symmetry test in a capuchin monkey

    PubMed Central

    de Faria Brino, Ana Leda; da Silva Campos, Rodolfo; de Faria Galvão, Olavo; McIlvane, William Jay

    2014-01-01

    A positive symmetry test result was obtained with a capuchin monkey that had previously exhibited virtually errorless AB and BA arbitrary matching-to-sample (MTS) with different stimuli. The symmetry test (BA) followed the acquisition of a new AB relation. It seemed possible, however, that the positive result could have occurred through the exclusion of previously defined comparison stimuli and not because the new AB and BA relations had the property of symmetry. To assess this possibility, a blank-comparison MTS procedure was implemented that permitted the separate assessment of select and reject (i.e., exclusion) control with both baseline and BA matching relations. In this assessment, the monkey did not exhibit reliable BA matching when exclusion was not possible, thus showing that the symmetry result was a false positive. However, the study demonstrated the feasibility of using a blank comparison MTS procedure with capuchins. The present results may set the stage for more successful methodology for establishing desired forms of relational stimulus control in capuchins and ultimately improving the assessment of relational learning capacity in that species, other nonhuman species, and nonverbal humans. PMID:25383161

  20. Automated detection of retinal nerve fiber layer defects on fundus images: false positive reduction based on vessel likelihood

    NASA Astrophysics Data System (ADS)

    Muramatsu, Chisako; Ishida, Kyoko; Sawada, Akira; Hatanaka, Yuji; Yamamoto, Tetsuya; Fujita, Hiroshi

    2016-03-01

    Early detection of glaucoma is important to slow down or cease progression of the disease and for preventing total blindness. We have previously proposed an automated scheme for detection of retinal nerve fiber layer defect (NFLD), which is one of the early signs of glaucoma observed on retinal fundus images. In this study, a new multi-step detection scheme was included to improve detection of subtle and narrow NFLDs. In addition, new features were added to distinguish between NFLDs and blood vessels, which are frequent sites of false positives (FPs). The result was evaluated with a new test dataset consisted of 261 cases, including 130 cases with NFLDs. Using the proposed method, the initial detection rate was improved from 82% to 98%. At the sensitivity of 80%, the number of FPs per image was reduced from 4.25 to 1.36. The result indicates the potential usefulness of the proposed method for early detection of glaucoma.

  1. SIB-BLAST: a web server for improved delineation of true and false positives in PSI-BLAST searches.

    PubMed

    Lee, Marianne M; Chan, Michael K; Bundschuh, Ralf

    2009-07-01

    A SIB-BLAST web server (http://sib-blast.osc.edu) has been established for investigators to use the SimpleIsBeautiful (SIB) algorithm for sequence-based homology detection. SIB was developed to overcome the model corruption frequently observed in the later iterations of PSI-BLAST searches. The algorithm compares resultant hits from the second iteration to the final iteration of a PSI-BLAST search, calculates the figure of merit for each 'overlapped' hit and re-ranks the hits according to their figure of merit. By validating hits generated from the last profile against hits from the first profile when the model is least corrupted, the true and false positives are better delineated, which in turn, improves the accuracy of iterative PSI-BLAST searches. Notably, this improvement to PSI-BLAST comes at minimal computational cost as SIB-BLAST utilizes existing results already produced in a PSI-BLAST search.

  2. False-positive liver scans due to portal hypertension: correlation with percutaneous transhepatic portograms in 33 patients

    SciTech Connect

    Takayasu, K.; Moriyama, N.; Suzuki, M.; Yamada, T.; Fukutake, T.; Shima, Y.; Kobayashi, C.; Musha, H.; Okuda, K.

    1983-04-01

    Tc-99m-phytate scanning of the liver and percutaneous transhepatic catheterization of the portal vein were performed in 33 patients--26 with cirrhosis, 3 with chronic active hepatitis, 2 with idiopathic portal hypertension, and 2 with unresolved acute hepatitis. A discrete defect in the porta hepatis area was seen in 6 of 28 patients who had portal vein pressure above 200 mm H2O. In 5 of the 6 patients with a false-positive scan, the umbilical portion of the left portal vein branch was dilated (larger than 25 x 20 mm) on the portogram, with or without a patent paraumbilical vein. The anatomical basis of this phenomenon is discussed, and it is suggested that this area be given special attention.

  3. Repeated cryostimulation improves position sense and simple reaction time

    PubMed Central

    Giemza, Czesław; Bieć, Ewa; Ostrowska, Bożena; Piechaczek, Bogusława; Sitny, Georg; Kuczyński, Michał

    2016-01-01

    [Purpose] Whole body cryotherapy has been shown to have many benefits, yet nothing is known if and how this modality can improve neuromuscular performance and retain those improvements. [Subjects and Methods] Joint position sense based on the bilateral knee joint matching test and simple reaction time was investigated in 25 young healthy adults who underwent an extended period of whole body cryostimulation. The measurements were taken at baseline and after 10, 20, and 30 whole body cryotherapy sessions, with three days elapsing after the last treatment, and comparing the results with 24 control subjects. [Results] Only when 20 sessions were completed did joint position sense and simple reaction time improve in the intervention group. After 30 sessions, the outcome was similar. Equal results were found at baseline and after 10 sessions in both groups, but the intervention group outstripped controls after 20 and 30 sessions in both joint position sense and simple reaction time. [Conclusion] These results indicate that the common standard of 10 sessions is insufficient, while approximately 20 sessions of whole body cryotherapy may efficiently enhance neuromuscular performance with an ability to sustain the effects for at least three days. PMID:27313369

  4. A false positive newborn screening result due to a complex allele carrying two frequent CF-causing variants.

    PubMed

    Bergougnoux, Anne; Boureau-Wirth, Amandine; Rouzier, Cécile; Altieri, Jean-Pierre; Verneau, Fanny; Larrieu, Lise; Koenig, Michel; Claustres, Mireille; Raynal, Caroline

    2016-05-01

    The detection of two frequent CFTR disease-causing variations in the context of a newborn screening program (NBS) usually leads to the diagnosis of cystic fibrosis (CF) and a relevant genetic counseling in the family. In the present study, CF-causing variants p.Phe508del (F508del) and c.3140-26A>G (3272-26A>G) were identified on a neonate with positive ImmunoReactive Trypsinogen test by the Elucigene™ CF30 kit. The CF diagnosis initially suggested, despite three inconclusive Sweat Chloride Tests (SCT), was finally ruled out after the familial segregation study combined with a negative SCT. Haplotype studies, based on the comparison of 80 p.Phe508del haplotypes, suggested a probable de novo occurrence of c.3140-26A>G on the p.Phe508del ancestral allele in this family. This false positive case emphasizes the importance of SCT in the NBS strategy. Moreover, it raises the need for familial segregation studies in CF and in overall molecular diagnosis strategy of autosomal recessive diseases. PMID:27117206

  5. Computer-aided detection of lung nodules: false positive reduction using a 3D gradient field method

    NASA Astrophysics Data System (ADS)

    Ge, Zhanyu; Sahiner, Berkman; Chan, Heang-Ping; Hadjiiski, Lubomir M.; Wei, Jun; Bogot, Naama; Cascade, Philip N.; Kazerooni, Ella A.; Zhou, Chuan

    2004-05-01

    We are developing a computer-aided detection system to aid radiologists in diagnosing lung cancer in thoracic computed tomographic (CT) images. The purpose of this study was to improve the false-positive (FP) reduction stage of our algorithm by developing and incorporating a gradient field technique. This technique extracts 3D shape information from the gray-scale values within a volume of interest. The gradient field feature values are higher for spherical objects, and lower for elongated and irregularly-shaped objects. A data set of 55 thin CT scans from 40 patients was used to evaluate the usefulness of the gradient field technique. After initial nodule candidate detection and rule-based first stage FP reduction, there were 3487 FP and 65 true positive (TP) objects in our data set. Linear discriminant classifiers with and without the gradient field feature were designed for the second stage FP reduction. The accuracy of these classifiers was evaluated using the area Az under the receiver operating characteristic (ROC) curve. The Az values were 0.93 and 0.91 with and without the gradient field feature, respectively. The improvement with the gradient field feature was statistically significant (p=0.01).

  6. Public health consequences of a false-positive laboratory test result for Brucella--Florida, Georgia, and Michigan, 2005.

    PubMed

    2008-06-01

    Human brucellosis, a nationally notifiable disease, is uncommon in the United States. Most human cases have occurred in returned travelers or immigrants from regions where brucellosis is endemic, or were acquired domestically from eating illegally imported, unpasteurized fresh cheeses. In January 2005, a woman aged 35 years who lived in Nassau County, Florida, received a diagnosis of brucellosis, based on results of a Brucella immunoglobulin M (IgM) enzyme immunoassay (EIA) performed in a commercial laboratory using analyte specific reagents (ASRs); this diagnosis prompted an investigation of dairy products in two other states. Subsequent confirmatory antibody testing by Brucella microagglutination test (BMAT) performed at CDC on the patient's serum was negative. The case did not meet the CDC/Council of State and Territorial Epidemiologists' (CSTE) definition for a probable or confirmed brucellosis case, and the initial EIA result was determined to be a false positive. This report summarizes the case history, laboratory findings, and public health investigations. CDC recommends that Brucella serology testing only be performed using tests cleared or approved by the Food and Drug Administration (FDA) or validated under the Clinical Laboratory Improvement Amendments (CLIA) and shown to reliably detect the presence of Brucella infection. Results from these tests should be considered supportive evidence for recent infection only and interpreted in the context of a clinically compatible illness and exposure history. EIA is not considered a confirmatory Brucella antibody test; positive screening test results should be confirmed by Brucella-specific agglutination (i.e., BMAT or standard tube agglutination test) methods.

  7. False positive control of activated voxels in single fMRI analysis using bootstrap resampling in comparison to spatial smoothing.

    PubMed

    Darki, Fahimeh; Oghabian, Mohammad Ali

    2013-10-01

    Functional magnetic resonance imaging (fMRI) is an effective tool for the measurement of brain neuronal activities. To date, several statistical methods have been proposed for analyzing fMRI datasets to select true active voxels among all the voxels appear to be positively activated. Finding a reliable and valid activation map is very important and becomes more crucial in clinical and neurosurgical investigations of single fMRI data, especially when pre-surgical planning requires accurate lateralization index as well as a precise localization of activation map. Defining a proper threshold to determine true activated regions, using common statistical processes, is a challenging task. This is due to a number of variation sources such as noise, artifacts, and physiological fluctuations in time series of fMRI data which affect spatial distribution of noise in an expected uniform activated region. Spatial smoothing methods are frequently used as a preprocessing step to reduce the effect of noise and artifacts. The smoothing may lead to a shift and enlargement of activation regions, and in some extend, unification of distinct regions. In this article, we propose a bootstrap resampling technique for analyzing single fMRI dataset with the aim of finding more accurate and reliable activated regions. This method can remove false positive voxels and present high localization accuracy in activation map without any spatial smoothing and statistical threshold setting.

  8. Resolution, target density and labeling effects in colocalization studies - suppression of false positives by nanoscopy and modified algorithms.

    PubMed

    Xu, Lei; Rönnlund, Daniel; Aspenström, Pontus; Braun, Laura J; Gad, Annica K B; Widengren, Jerker

    2016-03-01

    Colocalization analyses of fluorescence images are extensively used to quantify molecular interactions in cells. In recent years, fluorescence nanoscopy has approached resolutions close to molecular dimensions. However, the extent to which image resolution influences different colocalization estimates has not been systematically investigated. In this work, we applied simulations and resolution-tunable stimulated emission depletion microscopy to evaluate how the resolution, molecular density and label size of targeted molecules influence estimates of the most commonly used colocalization algorithms (Pearson correlation coefficient, Manders' M1 and M2 coefficients), as well as estimates by the image cross-correlation spectroscopy method. We investigated the practically measureable extents of colocalization for stimulated emission depletion microscopy with positive and negative control samples with an aim to identifying the strengths and weaknesses of nanoscopic techniques for colocalization studies. At a typical optical resolution of a confocal microscope (200-300 nm), our results indicate that the extent of colocalization is typically overestimated by the tested algorithms, especially at high molecular densities. Only minor effects of this kind were observed at higher resolutions (< 60 nm). By contrast, underestimation of colocalization may occur if the resolution is close to the size of the label/affinity molecules themselves. To suppress false positives at confocal resolutions and high molecular densities, we introduce a statistical variant of Costes' threshold searching algorithm, used in combination with correlation-based methods like the Pearson coefficient and the image cross-correlation spectroscopy approach, to set intensity thresholds separating background noise from signals.

  9. Pyrrolo[2,3-b]quinoxalines as inhibitors of firefly luciferase: their Cu-mediated synthesis and evaluation as false positives in a reporter gene assay.

    PubMed

    Nakhi, Ali; Rahman, Md Shafiqur; Kishore, Ravada; Meda, Chandana Lakshmi T; Deora, Girdhar Singh; Parsa, Kishore V L; Pal, Manojit

    2012-10-15

    2-Substituted pyrrolo[2,3-b]quinoxalines having free NH were prepared directly from 3-alkynyl-2-chloroquinoxalines in a single pot by using readily available and inexpensive methane sulfonamide (or p-toluene sulfonamide) as an ammonia surrogate. The reaction proceeded in the presence of Cu(OAc)(2) affording the desired product in moderate yield. The crystal structure analysis of a representative compound and its supramolecular interactions are presented. Some of the compounds synthesized exhibited inhibitory activities against luciferase that was supported by the predictive binding mode of these compounds with luciferase enzyme through molecular docking studies. The key observations disclosed here can alert users of luciferase reporter gene assays for possible false positive results due to the direct inhibition of luciferase.

  10. The prevalence of a false-positive myocardial perfusion stress SPET test in a skinny patient, induced by projection truncation.

    PubMed

    Tsougos, Ioannis; Alexiou, Sotiria; Theodorou, Kiki; Valotassiou, Varvara; Georgoulias, Panagiotis

    2015-01-01

    During the last decade, technical developments in myocardial perfusion single photon emission tomography (SPET) imaging systems have significantly improved the accuracy of diagnosing coronary artery disease. Nevertheless, the patient's position and/or the acquisition protocol can affect the studies' quality, possibly leading to misdiagnoses. In HJNM and in other journals the importance of proper positioning of the heart of the patient to be examined by myocardial perfusion SPET stress/rest testing, has been emphasized. According to our knowledge, only three cases of truncation artifact during SPET myocardial perfusion imaging acquired with original SPET cameras, related to improper positioning in very thin patients, have been reported. In all cases, patients were examined according to a single day stress/rest technetium-99m-sestamibi protocol, using a dual 90 degree detector system, equipped with high resolution, parallel-hole collimators. However, several published manuscripts have underlined the significance of appropriate patients' positioning in myocardial perfusion scintigraphy using dedicated, cadmium-zinc-telluride (CZT) or small field-of-view cardiac SPET systems. A typical case is that of a 47 years old man (height 187cm, weight 67kg), heavy smoker, with atypical chest pain. He exercised very well according to the Bruce protocol, achieving 95% of maximal age-predicted heart-rate and a technetium-99m-tetrofosmin ((99m)Tc-TF) myocardial perfusion imaging with 370MBq of (99m)Tc-TF followed with a dual head camera (Infinia GE, USA), equipped with low-energy, high-resolution, parallel-hole collimators at 90° (L-mode configuration). Projection images were obtained from 45° RAO to 45° LPO position, in step and shoot mode (60 projections, 30sec per projection; matrix 64×64 and zoom 1.3). Auto body contour was not used. Unprocessed raw data, showed neither patient motion nor significant extracardiac activity that could result in false positive defects on

  11. The prevalence of a false-positive myocardial perfusion stress SPET test in a skinny patient, induced by projection truncation.

    PubMed

    Tsougos, Ioannis; Alexiou, Sotiria; Theodorou, Kiki; Valotassiou, Varvara; Georgoulias, Panagiotis

    2015-01-01

    During the last decade, technical developments in myocardial perfusion single photon emission tomography (SPET) imaging systems have significantly improved the accuracy of diagnosing coronary artery disease. Nevertheless, the patient's position and/or the acquisition protocol can affect the studies' quality, possibly leading to misdiagnoses. In HJNM and in other journals the importance of proper positioning of the heart of the patient to be examined by myocardial perfusion SPET stress/rest testing, has been emphasized. According to our knowledge, only three cases of truncation artifact during SPET myocardial perfusion imaging acquired with original SPET cameras, related to improper positioning in very thin patients, have been reported. In all cases, patients were examined according to a single day stress/rest technetium-99m-sestamibi protocol, using a dual 90 degree detector system, equipped with high resolution, parallel-hole collimators. However, several published manuscripts have underlined the significance of appropriate patients' positioning in myocardial perfusion scintigraphy using dedicated, cadmium-zinc-telluride (CZT) or small field-of-view cardiac SPET systems. A typical case is that of a 47 years old man (height 187cm, weight 67kg), heavy smoker, with atypical chest pain. He exercised very well according to the Bruce protocol, achieving 95% of maximal age-predicted heart-rate and a technetium-99m-tetrofosmin ((99m)Tc-TF) myocardial perfusion imaging with 370MBq of (99m)Tc-TF followed with a dual head camera (Infinia GE, USA), equipped with low-energy, high-resolution, parallel-hole collimators at 90° (L-mode configuration). Projection images were obtained from 45° RAO to 45° LPO position, in step and shoot mode (60 projections, 30sec per projection; matrix 64×64 and zoom 1.3). Auto body contour was not used. Unprocessed raw data, showed neither patient motion nor significant extracardiac activity that could result in false positive defects on

  12. Computer-aided mass detection in mammography: False positive reduction via gray-scale invariant ranklet texture features

    SciTech Connect

    Masotti, Matteo; Lanconelli, Nico; Campanini, Renato

    2009-02-15

    In this work, gray-scale invariant ranklet texture features are proposed for false positive reduction (FPR) in computer-aided detection (CAD) of breast masses. Two main considerations are at the basis of this proposal. First, false positive (FP) marks surviving our previous CAD system seem to be characterized by specific texture properties that can be used to discriminate them from masses. Second, our previous CAD system achieves invariance to linear/nonlinear monotonic gray-scale transformations by encoding regions of interest into ranklet images through the ranklet transform, an image transformation similar to the wavelet transform, yet dealing with pixels' ranks rather than with their gray-scale values. Therefore, the new FPR approach proposed herein defines a set of texture features which are calculated directly from the ranklet images corresponding to the regions of interest surviving our previous CAD system, hence, ranklet texture features; then, a support vector machine (SVM) classifier is used for discrimination. As a result of this approach, texture-based information is used to discriminate FP marks surviving our previous CAD system; at the same time, invariance to linear/nonlinear monotonic gray-scale transformations of the new CAD system is guaranteed, as ranklet texture features are calculated from ranklet images that have this property themselves by construction. To emphasize the gray-scale invariance of both the previous and new CAD systems, training and testing are carried out without any in-between parameters' adjustment on mammograms having different gray-scale dynamics; in particular, training is carried out on analog digitized mammograms taken from a publicly available digital database, whereas testing is performed on full-field digital mammograms taken from an in-house database. Free-response receiver operating characteristic (FROC) curve analysis of the two CAD systems demonstrates that the new approach achieves a higher reduction of FP marks

  13. Predicting radiologists' true and false positive decisions in reading mammograms by using gaze parameters and image-based features

    NASA Astrophysics Data System (ADS)

    Gandomkar, Ziba; Tay, Kevin; Ryder, Will; Brennan, Patrick C.; Mello-Thoms, Claudia

    2016-03-01

    Radiologists' gaze-related parameters combined with image-based features were utilized to classify suspicious mammographic areas ultimately scored as True Positives (TP) and False Positives (FP). Eight breast radiologists read 120 two-view digital mammograms of which 59 had biopsy proven cancer. Eye tracking data was collected and nearby fixations were clustered together. Suspicious areas on mammograms were independently identified based on thresholding an intensity saliency map followed by automatic segmentation and pruning steps. For each radiologist reported area, radiologist's fixation clusters in the area, as well as neighboring suspicious areas within 2.5° of the center of fixation, were found. A 45-dimensional feature vector containing gaze parameters of the corresponding cluster along with image-based characteristics was constructed. Gaze parameters included total number of fixations in the cluster, dwell time, time to hit the cluster for the first time, maximum number of consecutive fixations, and saccade magnitude of the first fixation in the cluster. Image-based features consisted of intensity, shape, and texture descriptors extracted from the region around the suspicious area, its surrounding tissue, and the entire breast. For each radiologist, a userspecific Support Vector Machine (SVM) model was built to classify the reported areas as TPs or FPs. Leave-one-out cross validation was utilized to avoid over-fitting. A feature selection step was embedded in the SVM training procedure by allowing radial basis function kernels to have 45 scaling factors. The proposed method was compared with the radiologists' performance using the jackknife alternative free-response receiver operating characteristic (JAFROC). The JAFROC figure of merit increased significantly for six radiologists.

  14. Computerized lung nodule detection on thoracic CT images: combined rule-based and statistical classifier for false-positive reduction

    NASA Astrophysics Data System (ADS)

    Gurcan, Metin N.; Petrick, Nicholas; Sahiner, Berkman; Chan, Heang-Ping; Cascade, Philip N.; Kazerooni, Ella A.; Hadjiiski, Lubomir M.

    2001-07-01

    We are developing a computer-aided diagnosis (CAD) system for lung nodule detection on thoracic helical computed tomography (CT) images. In the first stage of this CAD system, lung regions are identified and suspicious structures are segmented. These structures may include true lung nodules or normal structures that consist mainly of vascular structures. We have designed rule-based classifiers to distinguish nodules and normal structures using 2D and 3D features. After rule-based classification, linear discriminant analysis (LDA) is used to further reduce the number of false positive (FP) objects. We have performed a preliminary study using CT images from 17 patients with 31 lung nodules. When only LDA classification was applied to the segmented objects, the sensitivity was 84% (26/31) with 2.53 (1549/612) FP objects per slice. When the LDA followed the rule-based classifier, the number of FP objects per slice decreased to 1.75 (1072/612) at the same sensitivity. These preliminary results demonstrate the feasibility of our approach for nodule detection and FP reduction on CT images. The inclusion of rule-based classification leads to an improvement in detection accuracy for the CAD system.

  15. Simplified false-positive reduction in computer-aided detection scheme of clustered microcalcifications in digital breast tomosynthesis

    NASA Astrophysics Data System (ADS)

    Jeong, Ji-Wook; Chae, Seung-Hoon; Lee, Sooyeul; Chae, Eun Young; Kim, Hak Hee; Choi, Young-Wook

    2015-03-01

    A computer-aided detection (CADe) system for clustered microcalcifications (MCs) in reconstructed digital breast tomosynthesis (DBT) volumes was suggested. The system consisted of prescreening, MC detecting, clustering, and falsepositive reduction steps. In the prescreening stage, the MC-like objects were enhanced by a multiscale-based 3D calcification response function. A connected component segmentation method was used to detect cluster seed objects, which were considered as potential clustering centers of MCs. Starting with each cluster seed object as the initial cluster center, a cluster candidate was formed by including nearby MC candidates within a 3D neighborhood of the cluster seed object satisfying the clustering criteria during the clustering step. The size and number of the clustered MCs in a cluster seed candidate were used to reduce the number of FPs. A bounding cube for each MCC was generated for each accepted seed candidates. Then, the overlapping cubes were combined and examined according to the FP reduction criteria. After FP reduction step, we obtained the average number of FPs of 2.47 per DBT volume with sensitivity of 83.3%. Our study indicates the simplified false-positive reduction approach applied to the detection of clustered MCs in DBT is promising as an efficient CADe system.

  16. Factors affecting recall rate and false positive fraction in breast cancer screening with breast tomosynthesis - A statistical approach.

    PubMed

    Rosso, Aldana; Lång, Kristina; Petersson, Ingemar F; Zackrisson, Sophia

    2015-10-01

    In this study, we investigate which factors affect the false positive fraction (FPF) for digital breast tomosynthesis (DBT) compared to digital mammography (DM) in a screening population by using classification and regression trees (C&RT) and binary marginal generalized linear models. The data was obtained from the Malmö Breast Tomosynthesis Screening Trial, which aimed to compare the performance of DBT to DM in breast cancer screening. By using data from the first half of the study population (7500 women), a tree with the recall probability for different groups was calculated. The effect of age and breast density on the FPF was estimated using a binary marginal generalized linear model. Our results show that breast density and breast cancer were the main factors influencing recall. The FPF is mainly affected by breast density and increases with breast density for DBT and DM. In conclusion, the results obtained with C&RT are easy to interpret and similar to those obtained using binary marginal generalized linear models. The FPF is approximately 40% higher for DBT compared to DM for all breast density categories.

  17. On the occurrence of false positives in tests of migration under an isolation-with-migration model.

    PubMed

    Hey, Jody; Chung, Yujin; Sethuraman, Arun

    2015-10-01

    The population genetic study of divergence is often carried out using a Bayesian genealogy sampler, like those implemented in ima2 and related programs, and these analyses frequently include a likelihood ratio test of the null hypothesis of no migration between populations. Cruickshank and Hahn (2014, Molecular Ecology, 23, 3133-3157) recently reported a high rate of false-positive test results with ima2 for data simulated with small numbers of loci under models with no migration and recent splitting times. We confirm these findings and discover that they are caused by a failure of the assumptions underlying likelihood ratio tests that arises when using marginal likelihoods for a subset of model parameters. We also show that for small data sets, with little divergence between samples from two populations, an excellent fit can often be found by a model with a low migration rate and recent splitting time and a model with a high migration rate and a deep splitting time. PMID:26456794

  18. Positivity constraints on initial spin observables in inclusive reactions.

    PubMed

    Soffer, Jacques

    2003-08-29

    For any inclusive reaction of the type A1(spin 1/2)+A2(spin 1/2)-->B+X, we derive new positivity constraints on spin observables and study their implications for theoretical models in view, in particular, of accounting for future data from the polarized pp collider at Brookhaven RHIC. We find that the single transverse spin asymmetry A(N), in the central region for several processes, for example, jet production, direct photon production, and lepton-pair production, is expected to be such that |A(N)| < or approximately 1/2, rather than the usual bound |A(N)|< or =1.

  19. Cell Shaving and False-Positive Control Strategies Coupled to Novel Statistical Tools to Profile Gram-Positive Bacterial Surface Proteomes.

    PubMed

    Solis, Nestor; Cordwell, Stuart J

    2016-01-01

    A powerful start to the discovery and design of novel vaccines, and for better understanding of host-pathogen interactions, is to profile bacterial surfaces using the proteolytic digestion of surface-exposed proteins under mild conditions. This "cell shaving" approach has the benefit of both identifying surface proteins and their surface-exposed epitopes, which are those most likely to interact with host cells and/or the immune system, providing a comprehensive overview of bacterial cell topography. An essential requirement for successful cell shaving is to account for (or minimize) cellular lysis that can occur during the shaving procedure and thus generate data that is biased towards non-surface (e.g., cytoplasmic) proteins. This is further complicated by the presence of "moonlighting" proteins, which are proteins predicted to be intracellular but with validated surface or extracellular functions. Here, we describe an optimized cell shaving protocol for Gram-positive bacteria that uses proteolytic digestion and a "false-positive" control to reduce the number of intracellular contaminants in these datasets. Released surface-exposed peptides are analyzed by liquid chromatography (LC) coupled to high-resolution tandem mass spectrometry (MS/MS). Additionally, the probabilities of proteins being surface exposed can be further calculated by applying novel statistical tools. PMID:27311663

  20. Multiresolution Local Binary Pattern texture analysis for false positive reduction in computerized detection of breast masses on mammograms

    NASA Astrophysics Data System (ADS)

    Choi, Jae Young; Kim, Dae Hoe; Choi, Seon Hyeong; Ro, Yong Man

    2012-03-01

    We investigated the feasibility of using multiresolution Local Binary Pattern (LBP) texture analysis to reduce falsepositive (FP) detection in a computerized mass detection framework. A new and novel approach for extracting LBP features is devised to differentiate masses and normal breast tissue on mammograms. In particular, to characterize the LBP texture patterns of the boundaries of masses, as well as to preserve the spatial structure pattern of the masses, two individual LBP texture patterns are then extracted from the core region and the ribbon region of pixels of the respective ROI regions, respectively. These two texture patterns are combined to produce the so-called multiresolution LBP feature of a given ROI. The proposed LBP texture analysis of the information in mass core region and its margin has clearly proven to be significant and is not sensitive to the precise location of the boundaries of masses. In this study, 89 mammograms were collected from the public MAIS database (DB). To perform a more realistic assessment of FP reduction process, the LBP texture analysis was applied directly to a total of 1,693 regions of interest (ROIs) automatically segmented by computer algorithm. Support Vector Machine (SVM) was applied for the classification of mass ROIs from ROIs containing normal tissue. Receiver Operating Characteristic (ROC) analysis was conducted to evaluate the classification accuracy and its improvement using multiresolution LBP features. With multiresolution LBP features, the classifier achieved an average area under the ROC curve, , z A of 0.956 during testing. In addition, the proposed LBP features outperform other state-of-the-arts features designed for false positive reduction.

  1. Mixture of expert artificial neural networks with ensemble training for reduction of various sources of false positives in CAD

    NASA Astrophysics Data System (ADS)

    Suzuki, Kenji; He, Lifeng; Khankari, Shweta; Ge, Liang; Verceles, Joel; Dachman, Abraham H.

    2007-03-01

    Our purpose was to reduce false-positive (FP) detections generated by a computerized lesion detection scheme by using a "mixture of expert" massive-training artificial neural networks (MTANNs). Multiple MTANNs were trained with "ensemble training" for reduction of diverse types of non-lesions. We started from a seed MTANN trained with lesions and non-lesions of a seed type. We applied the trained seed MTANN to lesions and various types of non-lesions to analyze the weakness of the seed MTANN. We arranged the output scores of the MTANN for lesions and non-lesions in an ascending order to form the score scale representing the degree of difficulty in distinction between lesions and non-lesions by the seed MTANN. The score scale was divided into several segments, and ten non-lesions were sampled from the center of each segment so that sets of non-lesion samples covered diverse difficulties. We trained several MTANNs with several sets of non-lesions so that each MTANN became an expert for the non-lesions at a certain level of difficulty. We then combined expert MTANNs with a mixing ANN to form a "mixture of expert" MTANNs. Our database consisted of CT colonography datasets acquired from 100 patients, including 26 polyps. We applied our initial CAD scheme to this CTC database. FP sources included haustral folds, stool, colonic walls, the ileocecal valves, and rectal tubes. The mixture of expert MTANNs distinguished all polyps correctly from more than 50% of the non-polyps. Thus, the mixture of expert MTANNs was able reduce one half of the FPs generated by a computerized polyp detection scheme while the original sensitivity was maintained. We compare the effectiveness of ensemble training with that of training with manually selected cases. The performance of the MTANNs with ensemble training was superior to that of the MTANNs trained with manually selected cases.

  2. False positive circumsporozoite protein ELISA: a challenge for the estimation of the entomological inoculation rate of malaria and for vector incrimination

    PubMed Central

    2011-01-01

    Background The entomological inoculation rate (EIR) is an important indicator in estimating malaria transmission and the impact of vector control. To assess the EIR, the enzyme-linked immunosorbent assay (ELISA) to detect the circumsporozoite protein (CSP) is increasingly used. However, several studies have reported false positive results in this ELISA. The false positive results could lead to an overestimation of the EIR. The aim of present study was to estimate the level of false positivity among different anopheline species in Cambodia and Vietnam and to check for the presence of other parasites that might interact with the anti-CSP monoclonal antibodies. Methods Mosquitoes collected in Cambodia and Vietnam were identified and tested for the presence of sporozoites in head and thorax by using CSP-ELISA. ELISA positive samples were confirmed by a Plasmodium specific PCR. False positive mosquitoes were checked by PCR for the presence of parasites belonging to the Haemosporidia, Trypanosomatidae, Piroplasmida, and Haemogregarines. The heat-stability and the presence of the cross-reacting antigen in the abdomen of the mosquitoes were also checked. Results Specimens (N = 16,160) of seven anopheline species were tested by CSP-ELISA for Plasmodium falciparum and Plasmodium vivax (Pv210 and Pv247). Two new vector species were identified for the region: Anopheles pampanai (P. vivax) and Anopheles barbirostris (Plasmodium malariae). In 88% (155/176) of the mosquitoes found positive with the P. falciparum CSP-ELISA, the presence of Plasmodium sporozoites could not be confirmed by PCR. This percentage was much lower (28% or 5/18) for P. vivax CSP-ELISAs. False positive CSP-ELISA results were associated with zoophilic mosquito species. None of the targeted parasites could be detected in these CSP-ELISA false positive mosquitoes. The ELISA reacting antigen of P. falciparum was heat-stable in CSP-ELISA true positive specimens, but not in the false positives. The heat

  3. Metabolism of fatty acid-labeled cerebroside sulfate in cultured cells from controls and metachromatic leukodystrophy patients. Use in the prenatal identification of a false positive fetus.

    PubMed

    Kudoh, T; Sattler, M; Malmstrom, J; Bitter, M A; Wenger, D A

    1981-11-01

    Metachromatic leukodystrophy is the name given to a group of diseases in patients having a deficiency of CS sulfatase activity. The diagnosis usually can be made by using leukocytes, urine, and cultured skin fibroblasts. The low level of enzyme activity can be measured with an artificial substrate, NCS, or suitably labeled CS. In a number of families, healthy carriers of this autosomal recessive disease have been found to have enzyme levels near those of affected patients. We prepared (14)C-stearic acid-labeled CS and studied its metabolism in cultured human cells from patients and controls, In vitro, CS sulfatase requires bile salts to stimulate the enzymatic reaction. The (14)C-CS also can be added to the medium on cultured cells, and its metabolism in the cells can be followed without the addition of bile salts. A child with late infantile MLD was identified by studies on urine and leukocytes. Studies on leukocytes from the parents revealed a very low enzyme level in the father (false positive) and a typical carrier level in the mother. A pregnancy in this family was monitored, and in vitro studies on cultured AFC revealed low CS and NCS sulfatase levels. However, the addition of (14)C-CS to the culture medium revealed normal metabolism in these cells. An unaffected fetus was predicted on the basis of the cell feeding studies. The couple elected to abort this pregnancy, and studies on the fetus confirmed it would not have been affected with MLD.

  4. Retroperitoneal Endometriosis: A Possible Cause of False Positive Finding at 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography

    PubMed Central

    Maffione, Anna Margherita; Panzavolta, Riccardo; Lisato, Laura Camilla; Ballotta, Maria; D'Isanto, Mariangela Zanforlini; Rubello, Domenico

    2015-01-01

    Endometriosis is a frequent and clinically relevant problem in young women. Laparoscopy is still the gold standard for the diagnosis of endometriosis, but frequently both morphologic and functional imaging techniques are involved in the diagnostic course before achieving a conclusive diagnosis. We present a case of a patient affected by infiltrating retroperitoneal endometriosis falsely interpreted as a malignant mass by contrast-enhanced magnetic resonance imaging and 18F-fluorodeoxyglucose positron emission tomography/computed tomography. PMID:26097425

  5. High Frequency of False-Positive Hepatitis C Virus Enzyme-Linked Immunosorbent Assay in Rakai, Uganda

    PubMed Central

    Mullis, Caroline E.; Laeyendecker, Oliver; Reynolds, Steven J.; Ocama, Ponsiano; Quinn, Jeffrey; Boaz, Iga; Gray, Ronald H.; Kirk, Gregory D.; Thomas, David L.; Quinn, Thomas C.; Stabinski, Lara

    2013-01-01

    The prevalence of hepatitis C virus (HCV) infection in sub-Saharan Africa remains unclear. We tested 1000 individuals from Rakai, Uganda, with the Ortho version 3.0 HCV enzyme-linked immunosorbent assay. All serologically positive samples were tested for HCV RNA. Seventy-six of the 1000 (7.6%) participants were HCV antibody positive; none were confirmed by detection of HCV RNA. PMID:24051866

  6. False-negative HIV-1 polymerase chain reaction in a 15-month-old boy with HIV-1 subtype C infection.

    PubMed

    Oladokun, R; Korsman, S; Ndabambi, N; Hsiao, N; Hans, L; Williamson, C; Abrahams, M-R; Eley, B

    2015-10-01

    Polymerase chain reaction (PCR) testing is the gold standard for determining the HIV status in children <18 months of age. However, when clinical manifestations are not consistent with laboratory results, additional investigation is required. We report a 15-month-old HIV-exposed boy referred to our hospital after he had been admitted several times for infectious diseases. A rapid antibody test on the child was positive, while routine diagnostic HIV PCRs using the Roche COBAS Ampliprep/COBAS TaqMan HIV Qual Test were negative at 6 weeks, 6 months, 7 months and 15 months. In addition, the same PCR test performed on the HIV-infected mother was also negative. Alternative PCR and viral load assays using different primer sets detected HIV RNA or proviral DNA in both child and mother. Gag sequences from the child and his mother classified both infections as HIV-1 subtype C, with very rare mutations that may have resulted in PCR assay primer/probe mismatch. Consequently, the child was commenced on antiretroviral therapy and made a remarkable recovery. These findings indicate that more reliable PCR assays capable of detecting a wide range of HIV subtypes are desirable to circumvent the clinical problems created by false-negative PCR results. PMID:26636158

  7. Prevalent false positives of azoospermia factor a (AZFa) microdeletions caused by single-nucleotide polymorphism rs72609647 in the sY84 screening of male infertility.

    PubMed

    Wu, Qing; Chen, Guo-Wu; Yan, Tao-Fei; Wang, Hui; Liu, Yu-Ling; Li, Zheng; Duan, Shi-Wei; Sun, Fei; Feng, Yun; Shi, Hui-Juan

    2011-11-01

    Multiplex polymerase chain reaction (PCR) has been widely used to detect Y-chromosome microdeletions, which is one of the major causes of male infertility. Both the European Academy of Andrology (EAA) and the European Molecular Genetics Quality Network (EMQN) have recommended the use of sY84 and sY86 markers for the detection of azoospermia factor a (AZFa) microdeletion during DNA testing for male infertility. In this study, a large-scale analysis of AZF microdeletion in a total of 630 Chinese males, including healthy semen donors (n=200), infertile males with normal sperm count (n=226) and patients with either nonobstructive azoospermia or severe oligozoospermia (n=204), was performed. A series of nine sequence-tagged site (STS) markers from the AZF region of the Y chromosome was used to detect microdeletions. All primers were designed based on the recommendations of the National Center for Biotechnology Information. An unusually high incidence (73/630, 11.6%) of sY84-absent but sY86-present genotypes was observed in the AZFa microdeletion screening. Sequencing the sY84-flanking region revealed a total of 73 patients with sY84-absent but sY86-present genotypes have a T-to-G transversion at the fifth base from the 5' end of the reverse sY84 primer. These prevalent false positives, which were not only observed in infertile men, but also observed in donors, resulted from a single-nucleotide polymorphism (SNP) named rs72609647 in the targeting sequence of the reverse sY84 primer. Our study suggests that a pre-screening of existence of rs72609647 polymorphism can prevent the frequent false positive results of AZFa microdeletions detection in the infertile Chinese males. Given the SNP rs72609647 was recently found in a deep sequencing of a Chinese individual, the current EAA and EMQN standards may need to be scrutinized among different populations to avoid the potential genetic variations in the primer binding sequences. PMID:21765443

  8. In Thyroidectomized Thyroid Cancer Patients, False-Positive I-131 Whole Body Scans Are Often Caused by Inflammation Rather Than Thyroid Cancer

    PubMed Central

    Garger, Yana Basis; Winfeld, Mathew; Friedman, Kent; Blum, Manfred

    2016-01-01

    Objective. To show that I-131 false-positive results on whole-body scans (WBSs) after thyroidectomy for thyroid cancer may be a result of inflammation unassociated with the cancer. Methods. We performed a retrospective image analysis of our database of thyroid cancer patients who underwent WBS from January 2008 to January 2012 to identify and stratify false positives. Results. A total of 564 patients underwent WBS during the study period; 96 patients were referred for 99 I-131 single-photon emission computed tomography (SPECT/CT) scans to better interpret cryptic findings. Among them, 73 scans were shown to be falsely positive; 40/73 or 54.7% of false-positive findings were a result of inflammation. Of the findings, 17 were in the head, 1 in the neck, 4 in the chest, 3 in the abdomen, and 14 in the pelvis; 1 had a knee abscess. Conclusions. In our series, inflammation caused the majority of false-positive WBSs. I-131 SPECT/CT is powerful in the differentiation of inflammation from thyroid cancer. By excluding metastatic disease, one can properly prognosticate outcome and avoid unnecessary, potentially harmful treatment of patients with thyroid cancer. PMID:26977418

  9. In Thyroidectomized Thyroid Cancer Patients, False-Positive I-131 Whole Body Scans Are Often Caused by Inflammation Rather Than Thyroid Cancer.

    PubMed

    Garger, Yana Basis; Winfeld, Mathew; Friedman, Kent; Blum, Manfred

    2016-01-01

    Objective. To show that I-131 false-positive results on whole-body scans (WBSs) after thyroidectomy for thyroid cancer may be a result of inflammation unassociated with the cancer. Methods. We performed a retrospective image analysis of our database of thyroid cancer patients who underwent WBS from January 2008 to January 2012 to identify and stratify false positives. Results. A total of 564 patients underwent WBS during the study period; 96 patients were referred for 99 I-131 single-photon emission computed tomography (SPECT/CT) scans to better interpret cryptic findings. Among them, 73 scans were shown to be falsely positive; 40/73 or 54.7% of false-positive findings were a result of inflammation. Of the findings, 17 were in the head, 1 in the neck, 4 in the chest, 3 in the abdomen, and 14 in the pelvis; 1 had a knee abscess. Conclusions. In our series, inflammation caused the majority of false-positive WBSs. I-131 SPECT/CT is powerful in the differentiation of inflammation from thyroid cancer. By excluding metastatic disease, one can properly prognosticate outcome and avoid unnecessary, potentially harmful treatment of patients with thyroid cancer.

  10. When a Little Knowledge Can Be Dangerous: False-Positive Diagnosis of Behavioral Variant Frontotemporal Dementia among Community Clinicians

    PubMed Central

    Shinagawa, Shunichiro; Catindig, Joseree Ann; Block, Nikolas R.; Miller, Bruce L.; Rankin, Katherine P.

    2016-01-01

    Background Accurate diagnosis of behavioral variant frontotemporal dementia (bvFTD) is important as patients’ behavioral symptoms have profound implications for their families and communities. Since the diagnosis of bvFTD derives from behavioral features, accurate identification of patients can be difficult for non-specialists. Concrete rates of diagnostic accuracy among non-specialists are unavailable. Methods To examine the accuracy of community clinicians’ diagnoses of bvFTD and to identify patient characteristics leading to misdiagnosis, we reviewed the charts and referral letters of 3,578 patients who were seen at our specialized center. Referral diagnosis and reasons, manifesting symptoms, demographic data, Mini-Mental State Examination score, Clinical Dementia Rating score and Neuropsychiatric Inventory score were extracted. Results 60% of patients assigned a single diagnosis of bvFTD by community clinicians did not have bvFTD according to specialists. Compared to specialist-confirmed bvFTD patients, false bvFTD patients were more likely to be depressed and to be non-Caucasian, showed less euphoria, apathy, disinhibition and abnormal eating behaviors, had milder disease severity and better overall cognition. bvFTD was mentioned by referring clinicians in 86% of specialist-confirmed bvFTD cases, but missed cases were called Alzheimer’s, Parkinson’s or Huntington’s disease, or progressive aphasia. Conclusion These results revealed a widespread lack of familiarity with core diagnostic symptoms among non-specialists and suggest that community clinicians require specialized diagnostic support before providing a definitive diagnosis of bvFTD. PMID:26741499

  11. ABIOTIC O{sub 2} LEVELS ON PLANETS AROUND F, G, K, AND M STARS: POSSIBLE FALSE POSITIVES FOR LIFE?

    SciTech Connect

    Harman, C. E.; Kasting, J. F.; Schwieterman, E. W.; Schottelkotte, J. C.

    2015-10-20

    In the search for life on Earth-like planets around other stars, the first (and likely only) information will come from the spectroscopic characterization of the planet's atmosphere. Of the countless number of chemical species terrestrial life produces, only a few have the distinct spectral features and the necessary atmospheric abundance to be detectable. The easiest of these species to observe in Earth's atmosphere is O{sub 2} (and its photochemical byproduct, O{sub 3}). However, O{sub 2} can also be produced abiotically by photolysis of CO{sub 2}, followed by recombination of O atoms with each other. CO is produced in stoichiometric proportions. Whether O{sub 2} and CO can accumulate to appreciable concentrations depends on the ratio of far-ultraviolet (FUV) to near-ultraviolet (NUV) radiation coming from the planet's parent star and on what happens to these gases when they dissolve in a planet's oceans. Using a one-dimensional photochemical model, we demonstrate that O{sub 2} derived from CO{sub 2} photolysis should not accumulate to measurable concentrations on planets around F- and G-type stars. K-star, and especially M-star planets, however, may build up O{sub 2} because of the low NUV flux from their parent stars, in agreement with some previous studies. On such planets, a “false positive” for life is possible if recombination of dissolved CO and O{sub 2} in the oceans is slow and if other O{sub 2} sinks (e.g., reduced volcanic gases or dissolved ferrous iron) are small. O{sub 3}, on the other hand, could be detectable at UV wavelengths (λ < 300 nm) for a much broader range of boundary conditions and stellar types.

  12. Efficacy of Several Serological Tests and Antigens for Diagnosis of Bovine Brucellosis in the Presence of False-Positive Serological Results Due to Yersinia enterocolitica O:9

    PubMed Central

    Muñoz, P. M.; Marín, C. M.; Monreal, D.; González, D.; Garin-Bastuji, B.; Díaz, R.; Mainar-Jaime, R. C.; Moriyón, I.; Blasco, J. M.

    2005-01-01

    Yersinia enterocolitica O:9 bears a smooth lipopolysaccharide (S-LPS) of Brucella sp. O-chain A + C/Y epitopic structure and is a cause of false-positive serological reactions (FPSR) in standard tests for cattle brucellosis. Brucella S-LPS, cross-reacting S-LPSs representing several O-chain epitope combinations, Brucella core lipid A epitopes (rough LPS), Brucella abortus S-LPS-derived polysaccharide, native hapten polysaccharide, rough LPS group 3 outer membrane protein complexes, recombinant BP26, and cytosolic proteins were tested in enzyme-linked immunosorbent assays (ELISA) and precipitation tests to detect cattle brucellosis (sensitivity) and to differentiate it from FPSR (specificity). No single serological test and antigen combination showed 100% sensitivity and specificity simultaneously. Immunoprecipitation tests with native hapten polysaccharide, counterimmunoelectrophoresis with cytosolic proteins, and a chaotropic ELISA with Brucella S-LPS were 100% specific but less sensitive than the Rose Bengal test, complement fixation, and indirect ELISA with Brucella S-LPSs and native hapten or S-LPS-derived polysaccharides. A competitive ELISA with Brucella S-LPS and M84 C/Y-specific monoclonal antibody was not 100% specific and was less sensitive than other tests. ELISA with Brucella suis bv. 2 S-LPS (deficient in C epitopes), Escherichia hermannii S-LPSs [lacking the contiguous α-(1-2)-linked perosamine residues characteristic of Y. enterocolitica S-LPS], BP26 recombinant protein, and Brucella cytosolic fractions did not provide adequate sensitivity/specificity ratios. Although no serological test and antigen combination fully resolved the diagnosis of bovine brucellosis in the presence of FPSR, some are simple and practical alternatives to the brucellin skin test currently recommended for differential diagnosis. PMID:15642999

  13. Detecting cocaine use? The autobiographical implicit association test (aIAT) produces false positives in a real-world setting

    PubMed Central

    2013-01-01

    Background The autobiographical Implicit Association Test (aIAT) is a novel application of the implicit association concept for detecting life events. It has been used to reveal concealed knowledge in clinical and forensic settings, including detecting drug use. In this study, we aimed to explore the functionality of the aIAT to identify drug use in real-world settings. Methods The study used mixed methodology with known groups of drug users and nonusers. Recreational cocaine users (n = 23) and non-users (n = 23) were recruited through ethnographic methodology and assessed using a bespoke brief aIAT for cocaine use. An identical aIAT test for heroin detection was also administered to a sub-sample of 10 cocaine users and 13 nonusers. The accuracy of the cocaine aIAT was measured through ROC analysis. Paradoxical aIAT results were explored by integrating craving, consumption measures and life-story interviews into the analysis. Results Whilst the two brief aIATs showed good concurrent validity for cocaine users by accurately detecting drug using status for 18 of the 23 users (78.3%), the test falsely reported 61% cocaine users in the non-user comparison group. The average D-scores were 0.257±0.246 for the cocaine users and 0.134±0.367 for the non-users, showing no discriminatory power (t(44) = 1.339, p = 0.187; AUC = 0.605, p = 0.223). Results were independent from craving and recent cocaine use. The comparison group’s cocaine and heroin aIAT scores correlated significantly (r(13) = 0.776, p = 0.002) whilst an accurate absence of such relationship was evidenced in the cocaine using sample (r(10) = 0.061, p = 0.866). Triangulation with life-story interviews suggests that in the absence of an autobiographical event, this test may measure an alternative cognitive construct linked to the Self-concept. Conclusion The aIAT is a variant of an attitude measure and can be better rationalized if propositional thinking is implied to explain outcomes. The Relational Frame

  14. False carbamazepine positives due to 10,11-dihydro-10-hydroxycarbamazepine breakdown in the GC-MS injector port.

    PubMed

    Lewis, Russell J; Angier, Mike K; Johnson, Robert D

    2014-10-01

    During the investigation of aviation accidents, postmortem specimens from accident victims are submitted to the Federal Aviation Administration's Civil Aerospace Medical Institute (CAMI) for toxicological analysis. A case recently received by CAMI screened positive for the anticonvulsant medication carbamazepine (CBZ; Tegretol(®)) by gas chromatography-mass spectrometry (GC-MS). The CBZ found during this routine screening procedure was subsequently confirmed using a CBZ-specific GC-MS procedure. It was later discovered that the accident victim had been prescribed oxcarbazepine (OXCBZ; Trileptal(®)). OXCBZ is structurally similar to CBZ and is metabolized by cytosolic enzymes in the liver to an active metabolite, 10,11-dihydro-10-hydroxycarbamazepine (DiCBZ). It was determined that the CBZ initially found in this case was present due to the thermal breakdown of DiCBZ in the GC-MS injector port. In the current study, this conversion was investigated and the percentage of CBZ formed at various injector port temperatures was determined. Additionally, these three compounds were quantified in nine fluid and tissue specimens from the case in question. Liquid chromatography-mass spectrometry was also incorporated to further demonstrate the absence/presence of CBZ in these samples.

  15. Quick and Easy Implementation of the Benjamini-Hochberg Procedure for Controlling the False Positive Rate in Multiple Comparisons. Teacher's Corner.

    ERIC Educational Resources Information Center

    Thissen, David; Steinberg, Lynne; Kuang, Daniel

    2002-01-01

    Illustrates that the Benjamini-Hochberg (B-H) procedure to controlling the false positive rate in multiple comparisons is easy to implement using widely available spreadsheet software. Shows that it is feasible to use the B-H procedure to augment or replace the Bonferroni technique. (SLD)

  16. Screening outcomes in older US women undergoing multiple mammograms in community practice: does interval, age, or comorbidity score affect tumor characteristics or false positive rates?

    PubMed

    Braithwaite, Dejana; Zhu, Weiwei; Hubbard, Rebecca A; O'Meara, Ellen S; Miglioretti, Diana L; Geller, Berta; Dittus, Kim; Moore, Dan; Wernli, Karen J; Mandelblatt, Jeanne; Kerlikowske, Karla

    2013-03-01

    Background Uncertainty exists about the appropriate use of screening mammography among older women because comorbid illnesses may diminish the benefit of screening. We examined the risk of adverse tumor characteristics and false positive rates according to screening interval, age, and comorbidity. Methods From January 1999 to December 2006, data were collected prospectively on 2993 older women with breast cancer and 137 949 older women without breast cancer who underwent mammography at facilities that participated in a data linkage between the Breast Cancer Surveillance Consortium and Medicare claims. Women were aged 66 to 89 years at study entry to allow for measurement of 1 year of preexisting illnesses. We used logistic regression analyses to calculate the odds of advanced (IIb, III, IV) stage, large (>20 millimeters) tumors, and 10-year cumulative probability of false-positive mammography by screening frequency (1 vs 2 years), age, and comorbidity score. The comorbidity score was derived using the Klabunde approximation of the Charlson score. All statistical tests were two-sided. Results Adverse tumor characteristics did not differ statistically significantly by comorbidity, age, or interval. Cumulative probability of a false-positive mammography result was higher among annual screeners than biennial screeners irrespective of comorbidity: 48.0% (95% confidence interval [CI] = 46.1% to 49.9%) of annual screeners aged 66 to 74 years had a false-positive result compared with 29.0% (95% CI = 28.1% to 29.9%) of biennial screeners. Conclusion Women aged 66 to 89 years who undergo biennial screening mammography have similar risk of advanced-stage disease and lower cumulative risk of a false-positive recommendation than annual screeners, regardless of comorbidity.

  17. Efficient detection of human circulating tumor cells without significant production of false-positive cells by a novel conditionally replicating adenovirus.

    PubMed

    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.

  18. Efficient detection of human circulating tumor cells without significant production of false-positive cells by a novel conditionally replicating adenovirus

    PubMed Central

    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

  19. False-positive serology following intravenous immunoglobulin and plasma exchange through transfusion of fresh frozen plasma in a patient with pemphigus vulgaris.

    PubMed

    Nomura, Hisashi; Honda, Haruki; Egami, Shohei; Yokoyama, Tomoaki; Fujimoto, Atsushi; Ishikawa, Makiko; Sugiura, Makoto

    2015-04-01

    Intravenous immunoglobulin therapy and plasma exchange through transfusion of fresh frozen plasma are therapeutic options for patients with refractory pemphigus vulgaris. Passive acquisition of various clinically important antibodies through these therapies can occur, leading to false serology and negatively affecting patients' clinical care. It is recommended that dermatologists recognize the possibility of these phenomena and interpret them appropriately. Here, we report false-positive serology following intravenous immunoglobulin therapy and plasma exchange through transfusion of fresh frozen plasma in a patient with refractory pemphigus vulgaris. We also discuss the measure for misinterpretation and unnecessary clinical intervention.

  20. A change in twist of actin provides the force for the extension of the acrosomal process in Limulus sperm: the false-discharge reaction.

    PubMed

    DeRosier, D J; Tilney, L G; Bonder, E M; Frankl, P

    1982-05-01

    One of the most spectacular motions is the generation of the acrosomal process in the limulus sperm. On contact with the egg, the sperm generates a 60-mum-long process that literally drills its way through the jelly surrounding the egg. This irresversible reaction takes only a few seconds. We suggested earlier that this motion is driven by a change in twist of the actin filaments comprising the acrosomal process. In this paper we analyze the so-called false discharge, a reversible reaction, in which the acrosomal filament bundle extends laterally from the base of the sperm and not anteriorly from the apex. Unlike the true discharge, which is straight, the false discharge is helical. Before extension, the filament bundle is coiled about the base of the sperm. In the coil, the bundle is not smoothly bent but consists of arms (straight segments) and elbows (corners) so that the coil looks like a 14-sided polygon. The extension of the false discharge works as follows: starting at the base of the bundle, the filaments change their twist which concomitantly changes the orientations of the elbows relative to each other; that is, in the coil, the elbows all like in a common plane, but after the change in twist, the plane of each elbow is rotated to be perpendicular to that of its neighbors. This change transforms the bundle from a compact coil into an extended left- handed helix. Because the basal end of the bundle is unconstrained, the extension is lateral. The true discharge works the same way but starts at the apical end of the bundle. The apical end, however, is constrained by its passage through the nuclear canal, which directs the extention anteriorly. Unlike the false discharge, during the true discharge the elbows are melted out, making the reaction irreversible. This study shows that rapid movement can be regenerated by actin without myosin and gives us insight into the molecular mechanism.

  1. Comparative analyses across cattle genders and breeds reveal the pitfalls caused by false positive and lineage-differential copy number variations.

    PubMed

    Zhou, Yang; Utsunomiya, Yuri T; Xu, Lingyang; Hay, El Hamidi Abdel; Bickhart, Derek M; Sonstegard, Tad S; Van Tassell, Curtis P; Garcia, Jose Fernando; Liu, George E

    2016-01-01

    We compared CNV region (CNVR) results derived from 1,682 Nellore cattle with equivalent results derived from our previous analysis of Bovine HapMap samples. By comparing CNV segment frequencies between different genders and groups, we identified 9 frequent, false positive CNVRs with a total length of 0.8 Mbp that were likely caused by assembly errors. Although there was a paucity of lineage specific events, we did find one 54 kb deletion on chr5 significantly enriched in Nellore cattle. A few highly frequent CNVRs present in both datasets were detected within genomic regions containing olfactory receptor, ATP-binding cassette, and major histocompatibility complex genes. We further evaluated their impacts on downstream bioinformatics and CNV association analyses. Our results revealed pitfalls caused by false positive and lineage-differential copy number variations and will increase the accuracy of future CNV studies in both taurine and indicine cattle. PMID:27381368

  2. Selecting At-Risk First-Grade Readers for Early Intervention: Eliminating False Positives and Exploring the Promise of a Two-Stage Gated Screening Process

    PubMed Central

    Compton, Donald L.; Fuchs, Douglas; Fuchs, Lynn S.; Bouton, Bobette; Gilbert, Jennifer K.; Barquero, Laura A.; Cho, Eunsoo; Crouch, Robert C.

    2010-01-01

    The purposes of this study were (a) to identify measures that when added to a base 1st-grade screening battery help eliminate false positives and (b) to investigate gains in efficiency associated with a 2-stage gated screening procedure. We tested 355 children in the fall of 1st grade, and assessed for reading difficulty at the end of 2nd grade. The base screening model, included measures of phonemic awareness, rapid naming skill, oral vocabulary, and initial word identification fluency (WIF). Short-term WIF progress monitoring (intercept and slope), dynamic assessment, running records, and oral reading fluency were each considered as an additional screening measure in contrasting models. Results indicated that the addition of WIF progress monitoring and dynamic assessment, but not running records or oral reading fluency, significantly decreased false positives. The 2-stage gated screening process using phonemic decoding efficiency in the first stage significantly reduced the number of children requiring the full screening battery. PMID:20689725

  3. Comparative analyses across cattle genders and breeds reveal the pitfalls caused by false positive and lineage-differential copy number variations

    PubMed Central

    Zhou, Yang; Utsunomiya, Yuri T.; Xu, Lingyang; Hay, El Hamidi abdel; Bickhart, Derek M.; Sonstegard, Tad S.; Van Tassell, Curtis P.; Garcia, Jose Fernando; Liu, George E.

    2016-01-01

    We compared CNV region (CNVR) results derived from 1,682 Nellore cattle with equivalent results derived from our previous analysis of Bovine HapMap samples. By comparing CNV segment frequencies between different genders and groups, we identified 9 frequent, false positive CNVRs with a total length of 0.8 Mbp that were likely caused by assembly errors. Although there was a paucity of lineage specific events, we did find one 54 kb deletion on chr5 significantly enriched in Nellore cattle. A few highly frequent CNVRs present in both datasets were detected within genomic regions containing olfactory receptor, ATP-binding cassette, and major histocompatibility complex genes. We further evaluated their impacts on downstream bioinformatics and CNV association analyses. Our results revealed pitfalls caused by false positive and lineage-differential copy number variations and will increase the accuracy of future CNV studies in both taurine and indicine cattle. PMID:27381368

  4. Positivity Constraints on Initial Spin Observables in Inclusive Reactions

    NASA Astrophysics Data System (ADS)

    Soffer, Jacques

    2003-08-01

    For any inclusive reaction of the type A1(spin 1/2)+A2(spin 1/2)→B+X, we derive new posi­tivity constraints on spin observables and study their implications for theoretical models in view, in particular, of accounting for future data from the polarized pp collider at Brookhaven RHIC. We find that the single transverse spin asymmetry AN, in the central region for several processes, for example, jet production, direct photon production, and lepton-pair production, is expected to be such that |AN|≲1/2, rather than the usual bound |AN|≤1.

  5. Intracardiac Shunt—Use of the Hydrogen-Sensitive Catheter to Clarify False Positive Diagnosis of Left-to-Right Shunt

    PubMed Central

    Stoike, Roger; Kuzman, William J.

    1967-01-01

    The charts of 142 patients who had diagnostic right heart catheterization with conventional oximetry, oxygen content determinations and hydrogen electrode curve recording for left-to-right shunt were reviewed. A false positive diagnosis of surgical significance would have been made in nine patients if the hydrogen electrode had not been used. In addition, a diagnosis of left-to-right shunt could have been made at the wrong chamber level in three additional cases. PMID:18730066

  6. Generic piperacillin/tazobactam is not associated with galactomannan false-positivity in adult patients with cancer: a case-control study.

    PubMed

    Ko, J-H; Peck, K R; Lee, W J; Lee, J Y; Cho, S Y; Ha, Y E; Kang, C-I; Chung, D R; Jung, C W; Kang, E-S; Song, J-H

    2015-07-01

    Recent products of piperacillin/tazobactam (PTZ) from the original manufacturer, previously considered a major cause of galactomannan (GM) false-positivity, are reported not to be related to it. However, data regarding generic PTZ are limited and controversial. To evaluate the effect of generic PTZ on GM false-positivity in Korea, we performed a case-control study in adult patients with cancer. A case-control study was designed. Electronic medical records of cancer patients who were admitted and tested for serum GM between March and June 2014 at a tertiary care university hospital were reviewed. During the study period, a single generic PTZ (C manufacturer, Korea) was used. Patients who received PTZ within 24 h prior to serum GM testing were enrolled. Age- and GM test date-matched non-PTZ patients were selected as controls. A total of 110 patients received PTZ within 24 h prior to serum GM testing during the study period. The GM optical density index (ODI) of the PTZ group did not vary significantly from that of the control group (p = 0.251). The percentage of false-positive patients in the PTZ group was also similar to that of the control group (p = 0.538). There was no statistical relationship between GM ODI titer and time interval from PTZ administration (p = 0.095) or cumulative PTZ dose (p = 0.416). In a case-control study that evaluated 220 patients, a generic PTZ in Korea was not related to GM false-positivity. PMID:25894983

  7. Generic piperacillin/tazobactam is not associated with galactomannan false-positivity in adult patients with cancer: a case-control study.

    PubMed

    Ko, J-H; Peck, K R; Lee, W J; Lee, J Y; Cho, S Y; Ha, Y E; Kang, C-I; Chung, D R; Jung, C W; Kang, E-S; Song, J-H

    2015-07-01

    Recent products of piperacillin/tazobactam (PTZ) from the original manufacturer, previously considered a major cause of galactomannan (GM) false-positivity, are reported not to be related to it. However, data regarding generic PTZ are limited and controversial. To evaluate the effect of generic PTZ on GM false-positivity in Korea, we performed a case-control study in adult patients with cancer. A case-control study was designed. Electronic medical records of cancer patients who were admitted and tested for serum GM between March and June 2014 at a tertiary care university hospital were reviewed. During the study period, a single generic PTZ (C manufacturer, Korea) was used. Patients who received PTZ within 24 h prior to serum GM testing were enrolled. Age- and GM test date-matched non-PTZ patients were selected as controls. A total of 110 patients received PTZ within 24 h prior to serum GM testing during the study period. The GM optical density index (ODI) of the PTZ group did not vary significantly from that of the control group (p = 0.251). The percentage of false-positive patients in the PTZ group was also similar to that of the control group (p = 0.538). There was no statistical relationship between GM ODI titer and time interval from PTZ administration (p = 0.095) or cumulative PTZ dose (p = 0.416). In a case-control study that evaluated 220 patients, a generic PTZ in Korea was not related to GM false-positivity.

  8. Unusual False Positive Radioiodine Uptake on (131)I Whole Body Scintigraphy in Three Unrelated Organs with Different Pathologies in Patients of Differentiated Thyroid Carcinoma: A Case Series.

    PubMed

    Ranade, Rohit; Pawar, Shwetal; Mahajan, Abhishek; Basu, Sandip

    2016-01-01

    Three cases with unusual false positive radioiodine uptake in three different organs and pathologies (infective old fibrotic lesion in the lung, simple liver cyst, and benign breast lesion) on iodine-131 ((131)I) whole body scintigraphy. Clinicoradiological correlation was undertaken in all three cases and the pathologies were ascertained. In all the three cases, single-photon emission computerized tomography-computed tomography (SPECT-CT) and ancillary imaging modalities were employed and were helpful in arriving at the final diagnosis.

  9. Image findings of a false positive radioactive iodine-131 uptake mimicking metastasis in pulmonary aspergillosis identified on single photon emission computed tomography-computed tomography.

    PubMed

    Karuppusamy, Kamaleshwaran Koramadai; Antony, Joppy; Radhakrishnan, E R; Shinto, Ajit Sugunan

    2015-01-01

    High doses of iodine-131 are commonly used in patients with differentiated thyroid cancer after total or subtotal thyroidectomy, in order to ablate the remaining cancer or normal thyroid tissue. Multiple different false-positive scans can occur in the absence of residual thyroid tissue or metastases. The authors present a case of abnormal uptake of radioactive iodine in the aspergilloma, potentially masquerading as pulmonary metastases.

  10. Unusual False Positive Radioiodine Uptake on 131I Whole Body Scintigraphy in Three Unrelated Organs with Different Pathologies in Patients of Differentiated Thyroid Carcinoma: A Case Series

    PubMed Central

    Ranade, Rohit; Pawar, Shwetal; Mahajan, Abhishek; Basu, Sandip

    2016-01-01

    Three cases with unusual false positive radioiodine uptake in three different organs and pathologies (infective old fibrotic lesion in the lung, simple liver cyst, and benign breast lesion) on iodine-131 (131I) whole body scintigraphy. Clinicoradiological correlation was undertaken in all three cases and the pathologies were ascertained. In all the three cases, single-photon emission computerized tomography-computed tomography (SPECT-CT) and ancillary imaging modalities were employed and were helpful in arriving at the final diagnosis. PMID:27134566

  11. Short-term Follow-up US Leads to Higher False-positive Results Without Detection of Structural Recurrences in PTMC.

    PubMed

    Yoon, Jung Hyun; Lee, Hye Sun; Kim, Eun-Kyung; Youk, Ji Hyun; Kim, Hyun Gi; Moon, Hee Jung; Kwak, Jin Young

    2016-01-01

    To investigate the value of the annual follow-up neck ultrasonography (US) for postoperative surveillance in patients with papillary thyroid microcarcinoma (PTMC). This retrospective study has been approved by our institutional review board (IRB) with waiver for informed consent. A total of 375 patients diagnosed as PTMCs, who underwent total thyroidectomy with radioiodine remnant ablation were included, to identify the recurrence rate and the false-positive rate of annual ultrasound. The number, interval, and the results of follow-up US or fine needle aspiration were obtained from electronic medical records. Four (1.1%, 4/375) recurrences were found 3 years after the initial treatment, and only 1 patient (0.3%, 1/375) had a metastatic lymph node larger than 8 mm in the shortest diameter on US found 7.6 years after initial treatment with biochemical abnormalities. Cumulative risk of having at least 1 false-positive exam was 8.3% by the 8th US, and 8.1% by the 8-9 year follow-up. Cox multivariate regression showed shorter interval of follow-up US and presence of lymph node metastasis at initial surgery are independent predictors affecting the cumulative false-positive results (hazard ratio [HR], 0.60; 95% confidence interval [CI]: 0.49-0.73; P < 0.001 and HR, 2.19; 95% CI: 1.01-4.75; P = 0.048, respectively). Short-term follow-up US can result in higher cumulative false-positive results without detection of meaningful recurrences in patients with PTMCs who do not have biochemical abnormalities.

  12. Selecting At-Risk First-Grade Readers for Early Intervention: Eliminating False Positives and Exploring the Promise of a Two-Stage Gated Screening Process

    ERIC Educational Resources Information Center

    Compton, Donald L.; Fuchs, Douglas; Fuchs, Lynn S.; Bouton, Bobette; Gilbert, Jennifer K.; Barquero, Laura A.; Cho, Eunsoo; Crouch, Robert C.

    2010-01-01

    The purposes of this study were (a) to identify measures that when added to a base 1st-grade screening battery help eliminate false positives and (b) to investigate gains in efficiency associated with a 2-stage gated screening procedure. We tested 355 children in the fall of 1st grade and assessed for reading difficulty at the end of 2nd grade.…

  13. Short-term Follow-up US Leads to Higher False-positive Results Without Detection of Structural Recurrences in PTMC

    PubMed Central

    Yoon, Jung Hyun; Lee, Hye Sun; Kim, Eun-Kyung; Youk, Ji Hyun; Kim, Hyun Gi; Moon, Hee Jung; Kwak, Jin Young

    2016-01-01

    Abstract To investigate the value of the annual follow-up neck ultrasonography (US) for postoperative surveillance in patients with papillary thyroid microcarcinoma (PTMC). This retrospective study has been approved by our institutional review board (IRB) with waiver for informed consent. A total of 375 patients diagnosed as PTMCs, who underwent total thyroidectomy with radioiodine remnant ablation were included, to identify the recurrence rate and the false-positive rate of annual ultrasound. The number, interval, and the results of follow-up US or fine needle aspiration were obtained from electronic medical records. Four (1.1%, 4/375) recurrences were found 3 years after the initial treatment, and only 1 patient (0.3%, 1/375) had a metastatic lymph node larger than 8 mm in the shortest diameter on US found 7.6 years after initial treatment with biochemical abnormalities. Cumulative risk of having at least 1 false-positive exam was 8.3% by the 8th US, and 8.1% by the 8–9 year follow-up. Cox multivariate regression showed shorter interval of follow-up US and presence of lymph node metastasis at initial surgery are independent predictors affecting the cumulative false-positive results (hazard ratio [HR], 0.60; 95% confidence interval [CI]: 0.49–0.73; P < 0.001 and HR, 2.19; 95% CI: 1.01–4.75; P = 0.048, respectively). Short-term follow-up US can result in higher cumulative false-positive results without detection of meaningful recurrences in patients with PTMCs who do not have biochemical abnormalities. PMID:26735548

  14. When the Single Matters more than the Group (II): Addressing the Problem of High False Positive Rates in Single Case Voxel Based Morphometry Using Non-parametric Statistics.

    PubMed

    Scarpazza, Cristina; Nichols, Thomas E; Seramondi, Donato; Maumet, Camille; Sartori, Giuseppe; Mechelli, Andrea

    2016-01-01

    In recent years, an increasing number of studies have used Voxel Based Morphometry (VBM) to compare a single patient with a psychiatric or neurological condition of interest against a group of healthy controls. However, the validity of this approach critically relies on the assumption that the single patient is drawn from a hypothetical population with a normal distribution and variance equal to that of the control group. In a previous investigation, we demonstrated that family-wise false positive error rate (i.e., the proportion of statistical comparisons yielding at least one false positive) in single case VBM are much higher than expected (Scarpazza et al., 2013). Here, we examine whether the use of non-parametric statistics, which does not rely on the assumptions of normal distribution and equal variance, would enable the investigation of single subjects with good control of false positive risk. We empirically estimated false positive rates (FPRs) in single case non-parametric VBM, by performing 400 statistical comparisons between a single disease-free individual and a group of 100 disease-free controls. The impact of smoothing (4, 8, and 12 mm) and type of pre-processing (Modulated, Unmodulated) was also examined, as these factors have been found to influence FPRs in previous investigations using parametric statistics. The 400 statistical comparisons were repeated using two independent, freely available data sets in order to maximize the generalizability of the results. We found that the family-wise error rate was 5% for increases and 3.6% for decreases in one data set; and 5.6% for increases and 6.3% for decreases in the other data set (5% nominal). Further, these results were not dependent on the level of smoothing and modulation. Therefore, the present study provides empirical evidence that single case VBM studies with non-parametric statistics are not susceptible to high false positive rates. The critical implication of this finding is that VBM can be used

  15. Chemical applicability domain of the Local Lymph Node Assay (LLNA) for skin sensitisation potency. Part 3. Apparent discrepancies between LLNA and GPMT sensitisation potential: False positives or differences in sensitivity?

    PubMed

    Roberts, David W; Schultz, Terry W; Api, Anne Marie

    2016-10-01

    The Local Lymph Node Assay (LLNA) is the gold standard regulatory toxicology test for skin sensitisation along with the guinea pig maximisation test (GPMT). Compared with the GPMT, LLNA uses fewer animals, it is quantitative, and it gives a numerical prediction of potency. However several concerns have been raised with this assay, mainly related to false positives and false negatives. Over the years, many authors, including the developers of the assay, have presented cases where there have been discrepancies between the GMPT and LLNA results. Several theories have been put forward for these discrepancies, the main one being the "over-sensitivity" of the GPMT. This paper analyses the data from a systematic study, published in three papers from 2008 to 2011, covering several classes of chemicals, in particular unsaturated fatty acids, sugar surfactants and ethoxylated alcohols, with many cases of chemicals testing positive in the LLNA being negative in the GPMT. Based on consideration of reaction chemistry and structural alerts, it is concluded that these discrepancies are not LLNA false positives, but can be rationalised in terms of the different protocols of the assays. PMID:27477089

  16. Facing the problem of "false positives": re-assessment and improvement of a multiplex RT-PCR procedure for the diagnosis of A. flavus mycotoxin producers.

    PubMed

    Degola, F; Berni, E; Spotti, E; Ferrero, I; Restivo, F M

    2009-02-28

    The aim of our research project was to consolidate a multiplex RT-PCR protocol to detect aflatoxigenic strains of Aspergillus flavus. Several independent A. flavus strains were isolated from corn and flour samples from the North of Italy and from three European countries. Aflatoxin producing/not producing phenotype was assessed by qualitative and quantitative assays at day five of growth in aflatoxin inducing conditions. Expression of 16 genes belonging to the aflatoxin cluster was assayed by multiplex or monomeric RT-PCR. There is a good correlation between gene expression and aflatoxin production. Strains that apparently transcribed all the relevant genes but did not release aflatoxin in the medium ("false positives") were re-assessed for mycotoxin production after extended growth in inducing condition. All the "false positive" strains in actual fact were positive when aflatoxin determination was performed after 10 days of growth. These strains should then be re-classified as "slow aflatoxin accumulators". To optimise the diagnostic procedure, a quintuplex RT-PCR procedure was designed consisting of a primer set directed against four informative aflatoxin cluster genes and the beta-tubulin gene as an internal amplification control. In conclusion we have provided evidence for the robustness and reliability of our RT-PCR protocol in discriminating mycotoxin producer from non-producer strains of A. flavus. and the molecular procedure we devised is a promising tool with which to screen and control the endemic population of A. flavus colonising different areas of the World.

  17. False-positive results in immunoglobulin M (IgM) toxoplasma antibody tests and importance of confirmatory testing: the Platelia Toxo IgM test.

    PubMed Central

    Liesenfeld, O; Press, C; Montoya, J G; Gill, R; Isaac-Renton, J L; Hedman, K; Remington, J S

    1997-01-01

    Although tests for detection of immunoglobulin M (IgM) toxoplasma antibodies have been reported to have a high degree of accuracy, it is well recognized by investigators in the United States and Europe that false-positive results may occur with many of these tests, at times to an alarming degree. Unfortunately, this information is not well documented in the literature. Studies on various toxoplasma IgM test kits are frequently flawed. The investigators often use reference tests which have not previously been carefully evaluated as well as sera that were not appropriate to answer the question of how often false-positive results might occur. We recently had the unique opportunity to evaluate the accuracy of the Platelia Toxo IgM test in 575 serum samples obtained during an outbreak of toxoplasmosis which occurred in 1995 in the Capital Regional District of British Columbia, Canada. When compared with results obtained in a reference IgM enzyme-linked immunosorbent assay (ELISA), the Platelia Toxo IgM test had a sensitivity of 99.4%, specificity of 49.2%, positive predictive value of 51.9%, negative predictive value of 99.3%, and an overall agreement of 67.0%. In an attempt to resolve discrepancies between these two tests, a serological profile (Sabin-Feldman dye test, IgA and IgE antibody tests, differential agglutination [AC/HS] test, and IgG avidity method) was performed. Of 153 serum samples that were positive in the Platelia Toxo IgM test and negative in the IgM ELISA, 71 (46.4%) were negative in the Sabin-Feldman dye test. Of the serum samples that were positive in the dye test, 77 (93.9%) had a serological profile most compatible with an infection acquired in the distant past. These results reveal high numbers of false-positive results in the Platelia Toxo IgM test and highlight the importance of appropriate evaluation of commercial tests that are currently being marked. Our results also emphasize the importance of confirmatory testing to determine whether the

  18. SERIAL NECK ULTRASOUND IS MORE LIKELY TO IDENTIFY FALSE-POSITIVE ABNORMALITIES THAN CLINICALLY SIGNIFICANT DISEASE IN LOW-RISK PAPILLARY THYROID CANCER PATIENTS

    PubMed Central

    Yang, Samantha Peiling; Bach, Ariadne M.; Tuttle, R. Michael; Fish, Stephanie A.

    2016-01-01

    Objective American Thyroid Association (ATA) low-risk papillary thyroid cancer (PTC) patients without structural evidence of disease on initial posttreatment evaluation have a low risk of recurrence. Despite this, most patients undergo frequent surveillance neck ultrasound (US). The objective of the study was to evaluate the clinical utility of routine neck US in ATA low-risk PTC patients with no structural evidence of disease after their initial thyroid surgery. Methods We performed a retrospective review of 171 ATA low-risk PTC patients after total thyroidectomy, with or without radioactive iodine (RAI) ablation, who had a neck US without suspicious findings after therapy. The main outcome measure was a comparison of the frequency of finding false-positive US abnormalities and the frequency of identifying structural disease recurrence. Results Over a median follow-up of 8 years, 171 patients underwent a median of 5 neck US (range 2–17). Structural recurrence with low-volume disease (≤1 cm) was identified in 1.2% (2/171) of patients at a median of 2.8 years (range 1.6–4.1 years) after their initial diagnosis. Recurrence was associated with rising serum thyroglobulin (Tg) level in 1 of the 2 patients and was detected without signs of biochemical recurrence in the other patient. Conversely, false-positive US abnormalities were identified in 67% (114/171) of patients after therapy, leading to additional testing without identifying clinically significant disease. Conclusion In ATA low-risk patients without structural evidence of disease on initial surveillance evaluation, routine screening US is substantially more likely to identify false-positive results than clinically significant structural disease recurrence. PMID:26372300

  19. Role of 5-HT2A and 5-HT2C receptors in the stimulus effects of hallucinogenic drugs. II: Reassessment of LSD false positives.

    PubMed

    Fiorella, D; Rabin, R A; Winter, J C

    1995-10-01

    In the context of animal studies of hallucinogens, an LSD-false positive is defined as a drug known to be devoid of hallucinogenic activity in humans but which nonetheless fully mimics LSD in animals. Quipazine, MK-212, lisuride, and yohimbine have all been reported to be LSD false positives. The present study was designed to determine whether these compounds also substitute for the stimulus effects of the more pharmacologically selective hallucinogen (-)DOM (0.56 mg/kg, 75-min pretreatment time). The LSD and (-)DOM stimuli fully generalized to quipazine (3.0 mg/kg) and lisuride (0.2 mg/kg), but only partially generalized to MK-212 (0.1-1.0 mg/kg) and yohimbine (2-20 mg/kg). In combination tests, pirenpirone (0.08 mg/kg), a compound with both D2 and 5-HT2A affinity, blocked the substitution of quipazine and lisuride for the (-)DOM stimulus. Ketanserin (2.5 mg/kg), an antagonist with greater than 1 order of magnitude higher affinity for 5-HT2A receptors than either 5-HT2C or D2 receptors, also fully blocked the substitution of these compounds for the (-)DOM stimulus, while the selective D2 antagonist thiothixene (0.1-1.0 mg/kg) failed to block the substitution of lisuride for the (-)DOM stimulus. These results suggest that quipazine and lisuride substitute for the stimulus properties of the phenylalkglamine hallucinogen (-)DOM via agonist activity at 5-HT2A receptors. In addition, these results suggest that 5-HT2A agonist activity may be required, but is not in itself sufficient, for indolamine and phenylalkglamine compounds to elicit hallucinations in humans. Finally, it is concluded that MK-212 and yohimbine are neither LSD nor (-)DOM false positives.

  20. A Discovery of a Candidate Companion to a Transiting System KOI-94: A Direct Imaging Study for a Possibility of a False Positive

    NASA Technical Reports Server (NTRS)

    Takahashi, Yasuhiro; Narita, Norio; Hirano, Teruyuki; Kuzuhara, Masayuki; Tamura, Motohide; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Sato, Bun'ei; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph C.; Currie, Thayne; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Henning, Thomas; Hodapp, Klaus W.; McElwain, Michael W.

    2013-01-01

    We report a discovery of a companion candidate around one of Kepler Objects of Interest (KOIs), KOI-94, and results of our quantitative investigation of the possibility that planetary candidates around KOI-94 are false positives. KOI-94 has a planetary system in which four planetary detections have been reported by Kepler, suggesting that this system is intriguing to study the dynamical evolutions of planets. However, while two of those detections (KOI-94.01 and 03) have been made robust by previous observations, the others (KOI-94.02 and 04) are marginal detections, for which future confirmations with various techniques are required. We have conducted high-contrast direct imaging observations with Subaru/HiCIAO in H band and detected a faint object located at a separation of approximately 0.6 sec from KOI-94. The object has a contrast of approximately 1 × 10(exp -3) in H band, and corresponds to an M type star on the assumption that the object is at the same distance of KOI-94. Based on our analysis, KOI-94.02 is likely to be a real planet because of its transit depth, while KOI-94.04 can be a false positive due to the companion candidate. The success in detecting the companion candidate suggests that high-contrast direct imaging observations are important keys to examine false positives of KOIs. On the other hand, our transit light curve reanalyses lead to a better period estimate of KOI-94.04 than that on the KOI catalogue and show that the planetary candidate has the same limb darkening parameter value as the other planetary candidates in the KOI-94 system, suggesting that KOI-94.04 is also a real planet in the system.

  1. A false positive case due to matrix interference in the analysis of ronidazole residues in muscle tissue using LC-MS/MS.

    PubMed

    Kumar, Praveen; Rúbies, Antoni; Centrich, Francesc; Companyó, Ramon

    2014-06-01

    In contrast with the information of the inspection body concerning the use of ronidazole, several non compliant muscle samples were detected using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method in accordance with confirmation criteria of Decision 2002/657/EC. This led to the suspicion that non compliance could be due to false positive results. In this context, a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method was developed and sample extracts were re-analyzed, resolving the co eluting isobaric interfering peak, which also has an interfering product ion with the transition product (m/z 201>140).

  2. A false positive case due to matrix interference in the analysis of ronidazole residues in muscle tissue using LC-MS/MS.

    PubMed

    Kumar, Praveen; Rúbies, Antoni; Centrich, Francesc; Companyó, Ramon

    2014-06-01

    In contrast with the information of the inspection body concerning the use of ronidazole, several non compliant muscle samples were detected using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method in accordance with confirmation criteria of Decision 2002/657/EC. This led to the suspicion that non compliance could be due to false positive results. In this context, a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method was developed and sample extracts were re-analyzed, resolving the co eluting isobaric interfering peak, which also has an interfering product ion with the transition product (m/z 201>140). PMID:24583330

  3. False-Positive Radioactive Iodine Uptake Mimicking Miliary Lung Metastases in a Patient Affected by Papillary Thyroid Cancer and IgA Deficiency.

    PubMed

    Demidowich, Andrew Paul; Kundu, Amartya; Reynolds, James C; Celi, Francesco S

    2016-09-01

    A 42-year-old female with immunoglobulin A deficiency and recurrent sinopulmonary infections underwent thyroidectomy for papillary thyroid cancer (PTC). Follow-up (123)I scintigraphy demonstrated diffuse pulmonary uptake, suggesting metastatic disease. However, subsequent pathologic, biochemical and radiographic testing proved that she was in fact disease free, and the initial (123)I pulmonary uptake was identified as a false positive. Inflammatory conditions may rarely cause iodine uptake in non-thyroidal tissues due to local retention, organification, and/or immunologic utilization. To avoid exposing patients to unnecessary treatments, it is critical for clinicians to recognize that comorbid pulmonary conditions may mimic metastatic PTC on radioiodine scintigraphy. PMID:27540434

  4. Standardization of Estrogen Receptor Measurement in Breast Cancer Suggests False-Negative Results Are a Function of Threshold Intensity Rather Than Percentage of Positive Cells

    PubMed Central

    Welsh, Allison W.; Moeder, Christopher B.; Kumar, Sudha; Gershkovich, Peter; Alarid, Elaine T.; Harigopal, Malini; Haffty, Bruce G.; Rimm, David L.

    2011-01-01

    Purpose Recent misclassification (false negative) incidents have raised awareness concerning limitations of immunohistochemistry (IHC) in assessment of estrogen receptor (ER) in breast cancer. Here we define a new method for standardization of ER measurement and then examine both change in percentage and threshold of intensity (immunoreactivity) to assess sources for test discordance. Methods An assay was developed to quantify ER by using a control tissue microarray (TMA) and a series of cell lines in which ER immunoreactivity was analyzed by quantitative immunoblotting in parallel with the automated quantitative analysis (AQUA) method of quantitative immunofluorescence (QIF). The assay was used to assess the ER protein expression threshold in two independent retrospective cohorts from Yale and was compared with traditional methods. Results Two methods of analysis showed that change in percentage of positive cells from 10% to 1% did not significantly affect the overall number of ER-positive patients. The standardized assay for ER on two Yale TMA cohorts showed that 67.9% and 82.5% of the patients were above the 2-pg/μg immunoreactivity threshold. We found 9.1% and 19.7% of the patients to be QIF-positive/IHC-negative, and 4.0% and 0.4% to be QIF-negative/IHC-positive for a total of 13.1% and 20.1% discrepant cases when compared with pathologists' judgment of threshold. Assessment of survival for both cohorts showed that patients who were QIF-positive/pathologist-negative had outcomes similar to those of patients who had positive results for both assays. Conclusion Assessment of intensity threshold by using a quantitative, standardized assay on two independent cohorts suggests discordance in the 10% to 20% range with current IHC methods, in which patients with discrepant results have prognostic outcomes similar to ER-positive patients with concordant results. PMID:21709197

  5. The number of genes changing expression after chronic exposure to code division multiple access or frequency DMA radiofrequency radiation does not exceed the false-positive rate.

    PubMed

    Whitehead, Timothy D; Moros, Eduardo G; Brownstein, Bernard H; Roti Roti, Joseph L

    2006-09-01

    Experiments with cultured C3H 10T 1/2 cells were performed to determine if exposure to cell phone radiofrequency (RF) radiations induce changes in gene expression. Following a 24 h exposure of 5 W/kg specific adsorption rate, RNA was extracted from the exposed and sham control cells for microarray analysis on Affymetrix U74Av2 Genechips. Cells exposed to 0.68 Gy of X-rays with a 4-h recovery were used as positive controls. The number of gene expression changes induced by RF radiation was not greater than the number of false positives expected based on a sham versus sham comparison. In contrast, the X-irradiated samples showed higher numbers of probe sets changing expression level than in the sham versus sham comparison.

  6. How to reduce false positive results when undertaking in vitro genotoxicity testing and thus avoid unnecessary follow-up animal tests: Report of an ECVAM Workshop.

    PubMed

    Kirkland, David; Pfuhler, Stefan; Tweats, David; Aardema, Marilyn; Corvi, Raffaella; Darroudi, Firouz; Elhajouji, Azeddine; Glatt, Hansruedi; Hastwell, Paul; Hayashi, Makoto; Kasper, Peter; Kirchner, Stephan; Lynch, Anthony; Marzin, Daniel; Maurici, Daniela; Meunier, Jean-Roc; Müller, Lutz; Nohynek, Gerhard; Parry, James; Parry, Elizabeth; Thybaud, Veronique; Tice, Ray; van Benthem, Jan; Vanparys, Philippe; White, Paul

    2007-03-30

    Workshop participants agreed that genotoxicity tests in mammalian cells in vitro produce a remarkably high and unacceptable occurrence of irrelevant positive results (e.g. when compared with rodent carcinogenicity). As reported in several recent reviews, the rate of irrelevant positives (i.e. low specificity) for some studies using in vitro methods (when compared to this "gold standard") means that an increased number of test articles are subjected to additional in vivo genotoxicity testing, in many cases before, e.g. the efficacy (in the case of pharmaceuticals) of the compound has been evaluated. If in vitro tests were more predictive for in vivo genotoxicity and carcinogenicity (i.e. fewer false positives) then there would be a significant reduction in the number of animals used. Beyond animal (or human) carcinogenicity as the "gold standard", it is acknowledged that genotoxicity tests provide much information about cellular behaviour, cell division processes and cellular fate to a (geno)toxic insult. Since the disease impact of these effects is seldom known, and a verification of relevant toxicity is normally also the subject of (sub)chronic animal studies, the prediction of in vivo relevant results from in vitro genotoxicity tests is also important for aspects that may not have a direct impact on carcinogenesis as the ultimate endpoint of concern. In order to address the high rate of in vitro false positive results, a 2-day workshop was held at the European Centre for the Validation of Alternative Methods (ECVAM), Ispra, Italy in April 2006. More than 20 genotoxicity experts from academia, government and industry were invited to review data from the currently available cell systems, to discuss whether there exist cells and test systems that have a reduced tendency to false positive results, to review potential modifications to existing protocols and cell systems that might result in improved specificity, and to review the performance of some new test systems

  7. The Application of Voltammetric Analysis of Δ(9) -THC for the Reduction of False Positive Results in the Analysis of Suspected Marijuana Plant Matter.

    PubMed

    Balbino, Marco A; de Oliveira, Laura S; Eleotério, Izabel C; Oiye, Erica N; Ribeiro, Maria F M; McCord, Bruce R; Ipolito, Antonio J; de Oliveira, Marcelo F

    2016-07-01

    The development of methodologies using inexpensive, fast, and reliable instrumention is desirable in illicit drug analysis. The purpose of this study was based on cyclic voltammetry technique to differentiate the electrochemical behavior of ∆(9) -THC, the psychoactive substance in marijuana, and five different extract plants to yield false positive results after analysis protocol for cannabinoids using thin-layer chromatography and Fast Blue B salt. After applying a deposition potential of -0.5 V in a glassy carbon working electrode, the results indicated an anodic peak current at 0.0 V versus Ag/AgCl after addition of ∆(9) -THC solution in the electrochemical cell, and limits of detection and quantification were 1.0 ng mL(-1) and 3.5 ng mL(-1) , respectively. Other interfering plants showed distinct amperometric responses. This methodology was useful to detect ∆(9) -THC even in the presence of the Fast Blue B salt, which avoided false positive results for all the studied extract plants. PMID:27364289

  8. The background rate of false positives: Combining simulations of gravitational wave events with an unsupervised algorithm for transient identification in crowded image-subtracted data

    NASA Astrophysics Data System (ADS)

    Ackley, Kendall; Eikenberry, Stephen; Klimenko, Sergey; LIGO Collaboration

    2016-03-01

    We are now entering the era of multimessenger gravitational wave (GW) astronomy with the completion of the first observing run of Advanced LIGO. Multiwavelength electromagnetic (EM) emission is expected to accompany gravitational radiation from compact object binary mergers, such as those between neutron stars and stellar-mass black holes, where Advanced LIGO is most sensitive to their detection. Attempting to perform EM follow-up over the 10-100s deg2 error regions will be faced with many challenges, including the identification and removal of O (105) false positive transients that appear as a commotion of background events and as image artifacts in crowded image-subtracted fields. We present an update to our automated unsupervised algorithm including how our pipeline uses the existing coherent WaveBurst pipeline in an attempt to develop optimized EM follow-up schema. Our end-to-end pipeline combines simulated GW events with actual observational data from a number of ground-based optical observatories, including PTF, ROTSE, and DECam. Our performance is reported both in terms of the number of coincident false positives as well as the efficiency of recovery.

  9. Using linked birth, notification, hospital and mortality data to examine false-positive meningococcal disease reporting and adjust disease incidence estimates for children in New South Wales, Australia.

    PubMed

    Gibson, A; Jorm, L; McIntyre, P

    2015-09-01

    Meningococcal disease is a rare, rapidly progressing condition which may be difficult to diagnose, disproportionally affects children, and has high morbidity and mortality. Accurate incidence estimates are needed to monitor the effectiveness of vaccination and treatment. We used linked notification, hospital, mortality and birth data for all children of an Australian state (2000-2007) to estimate the incidence of meningococcal disease. A total of 595 cases were notified, 684 cases had a hospital diagnosis, and 26 cases died from meningococcal disease. All deaths were notified, but only 68% (466/684) of hospitalized cases. Of non-notified hospitalized cases with more than one clinical admission, most (90%, 103/114) did not have meningococcal disease recorded as their final diagnosis, consistent with initial 'false-positive' hospital meningococcal disease diagnosis. After adjusting for false-positive rates in hospital data, capture-recapture estimation suggested that up to four cases of meningococcal disease may not have been captured in either notification or hospital records. The estimated incidence of meningococcal disease in NSW-born and -resident children aged 0-14 years was 5·1-5·4 cases/100 000 child-years at risk, comparable to international estimates using similar methods, but lower than estimates based on hospital data. PMID:25573266

  10. Investigation of false positives associated with loop-mediated isothermal amplification assays for detection of Toxoplasma gondii in archived tissue samples of captive felids.

    PubMed

    Suleman, Essa; Mtshali, Moses Sibusiso; Lane, Emily

    2016-09-01

    Toxoplasma gondii is a ubiquitous protozoan parasite that infects humans and many different animals, including felids. Many molecular and serologic tests have been developed for detection of T. gondii in a wide range of hosts. Loop-mediated isothermal amplification (LAMP) is a field-friendly technique that lacks the practical drawbacks of other molecular and serologic tests, and LAMP assays have been successfully developed for detection of T. gondii in fresh tissue samples. In the current study, both a previously published and a de-novo designed LAMP assay were compared to a quantitative real-time (q)PCR assay, for the detection of T. gondii in archived formalin-fixed, paraffin-embedded (FFPE) tissue samples from captive wildlife. The LAMP assays produced conflicting results, generating both false positives and false negatives. Furthermore, the LAMP assays were unable to positively identify samples with low levels of parasites as determined by qPCR and histopathology. Therefore, these LAMP assays may not be the most suitable assays for detection of T. gondii in archived FFPE and frozen tissue samples. PMID:27449130

  11. A transformer of molecular beacon for sensitive and real-time detection of phosphatases with effective inhibition of the false positive signals.

    PubMed

    Zhang, Chen; Su, Xin; Liang, Yuan; Zhu, Xiaocui; Song, Chen; Zhao, Meiping

    2011-10-15

    Molecular beacons (MBs) have shown great potential in measurement of enzyme activities. However, currently available methods for monitoring of phosphatases only use MBs as a signal reporter. Extra substrates for the phosphatases are needed to hybridize to the MB either as a primer or as a template. Moreover, few MB-based methods have been used to detect enzyme activities in real biological samples due to insufficient sensitivity or false positive interference signals caused by nonspecific nucleases. In this work, a novel type of fluorescent probe was designed and synthesized for monitoring of phosphatases by integrating the DNA substrate and the signaling structures into a single molecule. Such a new design not only significantly simplified the probing system and greatly enhanced the sensitivity, but also offered a practical way to guard against the false-positive signal problems in the application to real samples. The unique design of the assay format should be widely applicable to many other enzymatic assays using oligonucleotide fluorescent probes.

  12. The Application of Voltammetric Analysis of Δ(9) -THC for the Reduction of False Positive Results in the Analysis of Suspected Marijuana Plant Matter.

    PubMed

    Balbino, Marco A; de Oliveira, Laura S; Eleotério, Izabel C; Oiye, Erica N; Ribeiro, Maria F M; McCord, Bruce R; Ipolito, Antonio J; de Oliveira, Marcelo F

    2016-07-01

    The development of methodologies using inexpensive, fast, and reliable instrumention is desirable in illicit drug analysis. The purpose of this study was based on cyclic voltammetry technique to differentiate the electrochemical behavior of ∆(9) -THC, the psychoactive substance in marijuana, and five different extract plants to yield false positive results after analysis protocol for cannabinoids using thin-layer chromatography and Fast Blue B salt. After applying a deposition potential of -0.5 V in a glassy carbon working electrode, the results indicated an anodic peak current at 0.0 V versus Ag/AgCl after addition of ∆(9) -THC solution in the electrochemical cell, and limits of detection and quantification were 1.0 ng mL(-1) and 3.5 ng mL(-1) , respectively. Other interfering plants showed distinct amperometric responses. This methodology was useful to detect ∆(9) -THC even in the presence of the Fast Blue B salt, which avoided false positive results for all the studied extract plants.

  13. Strikingly high false positivity of surveillance FDG-PET/CT scanning among patients with diffuse large cell lymphoma in the rituximab era.

    PubMed

    Avivi, Irit; Zilberlicht, Ariel; Dann, Eldad J; Leiba, Ronit; Faibish, Tal; Rowe, Jacob M; Bar-Shalom, Rachel

    2013-05-01

    Predictive value (PV) of surveillance fluorodeoxyglucose positron emission tomography (FDG-PET) in patients with diffuse large B-cell lymphoma (DLBCL) treated with chemotherapy-rituximab (R) versus chemotherapy only, remains unclear. The aim of the current study was to compare the performance of surveillance PET in DLBCL patients receiving CHOP (cyclophosphamide, hydroxydaunorubicin hydrochloride, vincristine, and prednisone) alone versus CHOP-R. Institutional database was retrospectively searched for adults with newly diagnosed DLBCL, receiving CHOP or CHOP-R, who achieved complete remission and underwent surveillance PETs. Follow-up (FU) PET was considered positive for recurrence in case of an uptake unrelated to physiological or known benign process. Results were confirmed by biopsy, imaging and clinical FU. One hundred nineteen patients, 35 receiving CHOP and 84 CHOP-R, who underwent 422 FU-PETs, were analyzed. At a median PET-FU of 3.4 years, 31 patients relapsed (17 vs. 14, respectively; P = 0.02). PET detected all relapses, with no false-negative studies. Specificity and positive PV (PPV) were significantly lower for patients receiving CHOP-R vs. CHOP (84% vs. 87%, P = 0.023; 23% vs. 74%, P < 0.0001), reflecting a higher false-positive (FP) rate in subjects receiving CHOP-R (77% vs. 26%, P < 0.001). In the latter group, FP-rate remained persistently high up to 3 years post-therapy. Multivariate analysis confirmed rituximab to be the most significant predictor for FP-PET. In conclusion, routine surveillance FDG-PET is not recommended in DLBCL treated with rituximab; strict criteria identifying patients in whom FU-PET is beneficial are required. PMID:23423884

  14. False assumptions.

    PubMed

    Swaminathan, M

    1997-01-01

    Indian women do not have to be told the benefits of breast feeding or "rescued from the clutches of wicked multinational companies" by international agencies. There is no proof that breast feeding has declined in India; in fact, a 1987 survey revealed that 98% of Indian women breast feed. Efforts to promote breast feeding among the middle classes rely on such initiatives as the "baby friendly" hospital where breast feeding is promoted immediately after birth. This ignores the 76% of Indian women who give birth at home. Blaming this unproved decline in breast feeding on multinational companies distracts attention from more far-reaching and intractable effects of social change. While the Infant Milk Substitutes Act is helpful, it also deflects attention from more pressing issues. Another false assumption is that Indian women are abandoning breast feeding to comply with the demands of employment, but research indicates that most women give up employment for breast feeding, despite the economic cost to their families. Women also seek work in the informal sector to secure the flexibility to meet their child care responsibilities. Instead of being concerned about "teaching" women what they already know about the benefits of breast feeding, efforts should be made to remove the constraints women face as a result of their multiple roles and to empower them with the support of families, governmental policies and legislation, employers, health professionals, and the media. PMID:12321627

  15. Detection of human cytomegalovirus DNA in paraffin sections of human brain by polymerase chain reaction and the occurrence of false negative results.

    PubMed Central

    Gass, P; Kiessling, M; Schäfer, P; Mester, C; Schmitt, H P; Kühn, J E

    1993-01-01

    Paraffin-embedded necropsy material from 6 patients with human cytomegalovirus encephalitis (HCMVE) corroborated by immunocytochemistry and 11 control cases were examined for the presence of human cytomegalovirus (HCMV) DNA by a nested polymerase chain reaction (nPCR). A characteristic 183 base pair (bp) fragment of the HCMV genome could readily be amplified in 4 cases of HCMVE. In 2 cases of HCMVE, viral DNA could be demonstrated only sporadically by PCR, due most likely to inefficient DNA extraction or DNA degradation. All control cases remained negative. The nPCR provides a specific method for detecting HCMV DNA in routinely processed biopsy and necropsy material and may be used in archival tissues for the diagnosis of infection. Fixation of samples and DNA extraction are, however, crucial steps and require careful control if PCR is used for detection of HCMV, to avoid false negative results. Images PMID:8382271

  16. Filter-based feature selection and support vector machine for false positive reduction in computer-aided mass detection in mammograms

    NASA Astrophysics Data System (ADS)

    Nguyen, V. D.; Nguyen, D. T.; Nguyen, T. D.; Phan, V. A.; Truong, Q. D.

    2015-02-01

    In this paper, a method for reducing false positive in computer-aided mass detection in screening mammograms is proposed. A set of 32 features, including First Order Statistics (FOS) features, Gray-Level Occurrence Matrix (GLCM) features, Block Difference Inverse Probability (BDIP) features, and Block Variation of Local Correlation coefficients (BVLC) are extracted from detected Regions-Of-Interest (ROIs). An optimal subset of 8 features is selected from the full feature set by mean of a filter-based Sequential Backward Selection (SBS). Then, Support Vector Machine (SVM) is utilized to classify the ROIs into massive regions or normal regions. The method's performance is evaluated using the area under the Receiver Operating Characteristic (ROC) curve (AUC or AZ). On a dataset consisting about 2700 ROIs detected from mini-MIAS database of mammograms, the proposed method achieves AZ=0.938.

  17. Intensity of amnesia during hypnosis is positively correlated with estimated prevalence of sexual abuse and alien abductions: implications for the false memory syndrome.

    PubMed

    Dittburner, T L; Persinger, M A

    1993-12-01

    20 normal young women listened to an ambiguous story concerning a young boy who experienced fear, odd smells, and a smothering sensation during the night and skin lesions the next morning. After the Hypnotic Induction Profile (HIP) had been established, they were asked to estimate either the percentage prevalence of childhood sexual abuse or alien abduction in the general population. There were moderate (0.50) positive correlations between the subjects' estimates of prevalence and the amount of amnesia ("lost time") and indices of right-hemispheric anomalies (history of sensed presence and left-ear suppressions during a dichotic-listening task). Relevance of observations to formation of the False Memory Syndrome and to the development of nonpsychotic delusions is discussed.

  18. False-positive myeloperoxidase binding activity due to DNA/anti-DNA antibody complexes: a source for analytical error in serologic evaluation of anti-neutrophil cytoplasmic autoantibodies.

    PubMed

    Jethwa, H S; Nachman, P H; Falk, R J; Jennette, J C

    2000-09-01

    Anti-myeloperoxidase antibodies (anti-MPO) are a major type of anti-neutrophil cytoplasmic antibody (ANCA). While evaluating anti-MPO monoclonal antibodies from SCG/Kj mice, we observed several hybridomas that appeared to react with both MPO and DNA. Sera from some patients with systemic lupus erythematosus (SLE) also react with MPO and DNA. We hypothesized that the MPO binding activity is a false-positive result due to the binding of DNA, contained within the antigen binding site of anti-DNA antibodies, to the cationic MPO. Antibodies from tissue culture supernatants from 'dual reactive' hybridomas were purified under high-salt conditions (3 M NaCl) to remove any antigen bound to antibody. The MPO and DNA binding activity were measured by ELISA. The MPO binding activity was completely abrogated while the DNA binding activity remained. The MPO binding activity was restored, in a dose-dependent manner, by the addition of increasing amount of calf-thymus DNA (CT-DNA) to the purified antibody. Sera from six patients with SLE that reacted with both MPO and DNA were treated with DNase and showed a decrease in MPO binding activity compared with untreated samples. MPO binding activity was observed when CT-DNA was added to sera from SLE patients that initially reacted with DNA but not with MPO. These results suggest that the DNA contained within the antigen binding site of anti-DNA antibodies could bind to the highly cationic MPO used as substrate antigen in immunoassays, resulting in a false-positive test.

  19. Development of a method that eliminates false-positive results due to nerve growth factor interference in the assessment of fulranumab immunogenicity.

    PubMed

    Dai, Sheng; Schantz, Allen; Clements-Egan, Adrienne; Cannon, Michael; Shankar, Gopi

    2014-05-01

    Fulranumab, a human IgG2 monoclonal antibody that neutralizes nerve growth factor (NGF), is currently in development for the treatment of pain. Our initial immunogenicity test method was found to be prone to NGF interference, leading to a high apparent incidence of anti-drug antibody (ADA) in phase 1 studies. The ADA immunoassay comprised a homogeneous bridging electrochemiluminescence (ECL) format with biotin and ruthenium-labeled fulranumab bound together ("bridged") by ADA in test samples for detection. In this assay, NGF produced a false-positive signal due to its ability to bridge fulranumab molecules. Thus, we developed a specificity assay to eliminate the NGF false-positive results. We encountered the challenge of eliminating drug interference as well as drug target interference, and discovered that the acid-dissociation-based pretreatment of samples used for mitigating drug interference dramatically increased drug target interference. Several strategies were investigated to eliminate the NGF interference; yet only one strategy specifically removed NGF and produced true fulranumab-specific ADA results by using competitive inhibition with fulranumab and utilizing an alternative NGF binding antibody to eliminate NGF interference. Using this new method, we confirmed that the high apparent anti-fulranumab antibody incidence (>60%) in clinical study samples was in fact due to fulranumab-bound NGF released during the acid-dissociation step of the ADA testing method. We conclude that our revised method accurately identifies anti-fulranumab antibodies by incorporating steps to eliminate fulranumab and NGF interference. We advise that acid-dissociation pretreatment must not be universally applied to improve ADA assays without investigating its bioanalytical risks versus benefits.

  20. Analysis and solution of false-positives when testing CVA16 sera using an antibody assay against the EV71 virus.

    PubMed

    Wang, Changbing; You, Aiping; Tian, Xingui; Zhao, Mingqi; Chen, Yi; Lin, Tao; Zheng, Jianbin; Xiao, Misi; Zhang, Yingying; Kuang, Lu; Zhou, Zhenwen; Zhu, Bing

    2013-09-01

    Hand, foot and mouth disease (HFMD) in humans is caused mainly by Enterovirus 71(EV71) and Coxsackievirus A16 (CVA16). EV71 is associated with severe HFMD cases but not CVA16. Use of IgM-capture enzyme-linked immunosorbent assay (ELISA) is important for the early diagnosis of EV71 infection, but cross-reactivity of the anti-CVA16 IgM antibody with EV71 produces false-positive results. In this report, we designed a new EV71 IgM-capture ELISA method using the EV71 VP1 peptide instead of the EV71 virion as the detectable antigen, and tested sera from patients infected with EV71 or CVA16. The results showed that acute sera from 76 EV71-infected patients had similar sensitivity for virus detection (98.68%) or VP1 detection (97.37%). When acute sera from patients infected with CVA16 were used, significant differences between the two methods were observed. The cross-reactivity rate of the virus detection method was 29.4% (5/17), but no cross-reactivity was observed using the VP1 detection method. Western immunoblotting demonstrated that EV71 VP3 cross-reacted with part of the CVA16 IgM antibody. The results demonstrate that EV71 VP3 is the cross-reactive antigen in the EV71 IgM-capture ELISA when testing CVA16 sera using the virus-antibody detection method. The problem of false-positive results was resolved by using the VP1 peptide as the detectable antigen.

  1. Predictors of Pertussis Polymerase Chain Reaction Positive Results in Minnesota, 2005-2009.

    PubMed

    McMahon, Melissa; Kulasingam, Shalini; Kenyon, Cynthia; Miller, Claudia; Ehresmann, Kristen

    2015-11-01

    Predictors of polymerase chain reaction (PCR) positivity for pertussis were assessed using Minnesota active surveillance data. Report of an exposure to pertussis and testing within the optimal time frame of ≤2 weeks were significantly associated with testing PCR positive, emphasizing the importance of asking about epidemiological factors when assessing patients for pertussis, and timely PCR testing.

  2. Upward creep of the heart: A frequent source of false-positive reversible defects during thallium-201 stress-redistribution SPECT

    SciTech Connect

    Friedman, J.; Van Train, K.; Maddahi, J.; Rozanski, A.; Prigent, F.; Bietendorf, J.; Waxman, A.; Berman, D.S. )

    1989-10-01

    A new cause of artifactual {sup 201}Tl defects on single photon emission computed tomography (SPECT) termed upward creep of the heart is described. In 102 consecutive patients undergoing {sup 201}Tl SPECT, 30 (29%) demonstrated upward creep defined by an upward movement of the heart of greater than or equal to 2 pixels during acquisition. In 45 consecutive patients with a less than 5% likelihood of coronary artery disease, 17 (38%) had upward creep. Of these nine had reversible {sup 201}Tl defects localized to the inferior and basal inferoseptal walls, while none of the 28 without upward creep had defects. The 17 low likelihood patients with upward creep had longer exercise duration and higher peak heart rate than those without upward creep. In five additional low likelihood patients with upward creep in whom imaging was immediately repeated, the upward creep pattern disappeared on the repeated images. After we changed our test protocol to begin imaging 15 min postexercise, only five (14%) of 36 low likelihood patients tested demonstrated upward creep. Upward creep is probably related to a transient increase in mean total lung volume early following exhaustive exercise, resulting in a mean lower position of the diaphragm (and thus the heart) at the beginning of imaging. The frequency of this source of false-positive {sup 201}Tl studies can be reduced by delaying SPECT acquisition until 15 min postexercise.

  3. False memories in schizophrenia.

    PubMed

    Moritz, Steffen; Woodward, Todd S; Cuttler, Carrie; Whitman, Jennifer C; Watson, Jason M

    2004-04-01

    In prior studies, it was observed that patients with schizophrenia show abnormally high knowledge corruption (i.e., high-confident errors expressed as a percentage of all high-confident responses were increased for schizophrenic patients relative to controls). The authors examined the conditions under which excessive knowledge corruption occurred using the Deese-Roediger-McDermott paradigm. Whereas knowledge corruption in schizophrenia was significantly greater for false-negative errors relative to controls, no group difference occurred for false-positive errors. The groups showed a comparable high degree of confidence for false-positive recognition of critical lure items. Similar to findings collected in elderly participants, patients, but not controls, showed a strong positive correlation between the number of recognized studied items and false-positive recognition of the critical lure.

  4. In-Flight Position Calibration of the Cassini Articulated Reaction Wheel Assembly

    NASA Technical Reports Server (NTRS)

    Brown, Todd S.

    2012-01-01

    NASA's long-lived Cassini-Huygens spacecraft is currently in its 14th year of flight and in the midst of its second, and final, extended mission. Cassini is a massive interplanetary spacecraft that is three axis stabilized and can maintain attitude control using either its reaction control system thrusters or using reaction wheel control. Cassini has four identical reaction wheels, of which three are mutually orthogonal and have a fixed orientation. The fourth reaction wheel has an articulation motor that allows this reaction wheel to be aligned with the momentum direction of any of the other three fixed reaction wheels. The articulation motor allows this reaction wheel to be used as a replacement for any of the other three wheels without any performance degradation. However, due to limitations in the design of this backup system, there are few telemetric indications of the orientation of this reaction wheel following an articulation. This investigation serves to outline the procedures that have been developed by the Cassini Attitude and Articulation Control Subsystem to calibrate the position of the articulated reaction wheel assembly in the event that the momentum direction of this reaction wheel must be reoriented.

  5. Massive-training artificial neural network (MTANN) for reduction of false positives in computer-aided detection of polyps: Suppression of rectal tubes

    SciTech Connect

    Suzuki, Kenji; Yoshida, Hiroyuki; Naeppi, Janne; Dachman, Abraham H.

    2006-10-15

    One of the limitations of the current computer-aided detection (CAD) of polyps in CT colonography (CTC) is a relatively large number of false-positive (FP) detections. Rectal tubes (RTs) are one of the typical sources of FPs because a portion of a RT, especially a portion of a bulbous tip, often exhibits a cap-like shape that closely mimics the appearance of a small polyp. Radiologists can easily recognize and dismiss RT-induced FPs; thus, they may lose their confidence in CAD as an effective tool if the CAD scheme generates such ''obvious'' FPs due to RTs consistently. In addition, RT-induced FPs may distract radiologists from less common true positives in the rectum. Therefore, removal RT-induced FPs as well as other types of FPs is desirable while maintaining a high sensitivity in the detection of polyps. We developed a three-dimensional (3D) massive-training artificial neural network (MTANN) for distinction between polyps and RTs in 3D CTC volumetric data. The 3D MTANN is a supervised volume-processing technique which is trained with input CTC volumes and the corresponding ''teaching'' volumes. The teaching volume for a polyp contains a 3D Gaussian distribution, and that for a RT contains zeros for enhancement of polyps and suppression of RTs, respectively. For distinction between polyps and nonpolyps including RTs, a 3D scoring method based on a 3D Gaussian weighting function is applied to the output of the trained 3D MTANN. Our database consisted of CTC examinations of 73 patients, scanned in both supine and prone positions (146 CTC data sets in total), with optical colonoscopy as a reference standard for the presence of polyps. Fifteen patients had 28 polyps, 15 of which were 5-9 mm and 13 were 10-25 mm in size. These CTC cases were subjected to our previously reported CAD scheme that included centerline-based segmentation of the colon, shape-based detection of polyps, and reduction of FPs by use of a Bayesian neural network based on geometric and texture

  6. Combining multiple feature representations and AdaBoost ensemble learning for reducing false-positive detections in computer-aided detection of masses on mammograms.

    PubMed

    Choi, Jae Young; Kim, Dae Hoe; Plataniotis, Konstantinos N; Ro, Yong Man

    2012-01-01

    One of the drawbacks of current Computer-aided Detection (CADe) systems is a high number of false-positive (FP) detections, especially for detecting mass abnormalities. In a typical CADe system, classifier design is one of the key steps for determining FP detection rates. This paper presents the effective classifier ensemble system for tackling FP reduction problem in CADe. To construct ensemble consisting of correct classifiers while disagreeing with each other as much as possible, we develop a new ensemble construction solution that combines data resampling underpinning AdaBoost learning with the use of different feature representations. In addition, to cope with the limitation of weak classifiers in conventional AdaBoost, our method has an effective mechanism for tuning the level of weakness of base classifiers. Further, for combining multiple decision outputs of ensemble members, a weighted sum fusion strategy is used to maximize a complementary effect for correct classification. Comparative experiments have been conducted on benchmark mammogram dataset. Results show that the proposed classifier ensemble outperforms the best single classifier in terms of reducing the FP detections of masses.

  7. Controlling false-positive results obtained with the Hodge and Masuda assays for detection of class a carbapenemase in species of enterobacteriaceae by incorporating boronic Acid.

    PubMed

    Pasteran, Fernando; Mendez, Tania; Rapoport, Melina; Guerriero, Leonor; Corso, Alejandra

    2010-04-01

    The modified Hodge method (MHT) has been recommended by the CLSI for confirmation of suspected class A carbapenemase production in species of Enterobacteriaceae. This test and the Masuda method (MAS) have advantages over traditional phenotypic methods in that they directly analyze carbapenemase activity. In order to identify the potential interferences of these tests, we designed a panel composed of diverse bacterial genera with distinct carbapenem susceptibility patterns (42 carbapenemase producers and 48 nonproducers). About 25% of results among carbapenemase nonproducers, mainly strains harboring CTX-M and AmpC hyperproducers, were observed to be false positive. Subsequently, we developed an optimized approach for more-accurate detection of suspicious isolates of carbapenemase by addition of boronic acid (BA) derivatives (reversible inhibitor of class A carbapenemases and AmpC cephalosporinases) and oxacillin (inhibitor of AmpCs enzymes). The use of the modified BA- and oxacillin-based MHT and MAS resulted in high sensitivity (>90%) and specificity (100%) for class A carbapenemase detection. By use of these methodologies, isolates producing KPCs and GES, Sme, IMI, and NMC-A carbapenemases were successfully distinguished from those producing other classes of ss-lactamases (extended-spectrum beta-lactamases [ESBLs], AmpC beta-lactamases, metallo-beta-lactamases [MBLs], etc.). These methods will provide the fast and useful information needed for targeting of antimicrobial therapy and appropriate infection control.

  8. Specificity and false positive rates of the Test of Memory Malingering, Rey 15-item Test, and Rey Word Recognition Test among forensic inpatients with intellectual disabilities.

    PubMed

    Love, Christopher M; Glassmire, David M; Zanolini, Shanna Jordan; Wolf, Amanda

    2014-10-01

    This study evaluated the specificity and false positive (FP) rates of the Rey 15-Item Test (FIT), Word Recognition Test (WRT), and Test of Memory Malingering (TOMM) in a sample of 21 forensic inpatients with mild intellectual disability (ID). The FIT demonstrated an FP rate of 23.8% with the standard quantitative cutoff score. Certain qualitative error types on the FIT showed promise and had low FP rates. The WRT obtained an FP rate of 0.0% with previously reported cutoff scores. Finally, the TOMM demonstrated low FP rates of 4.8% and 0.0% on Trial 2 and the Retention Trial, respectively, when applying the standard cutoff score. FP rates are reported for a range of cutoff scores and compared with published research on individuals diagnosed with ID. Results indicated that although the quantitative variables on the FIT had unacceptably high FP rates, the TOMM and WRT had low FP rates, increasing the confidence clinicians can place in scores reflecting poor effort on these measures during ID evaluations. PMID:24671735

  9. False-positive magnetic resonance imaging findings in follow-up of pediatric patients with tumors of the central nervous system

    PubMed Central

    De Oliveira, Satiro Nakamura; Gonzalez-Gomez, Ignacio; Panigrahy, Ashok; Krieger, Mark; McComb, Gordon; Finlay, Jonathan L; Dhall, Girish

    2016-01-01

    Management of patients with central nervous system tumors relies largely on magnetic resonance imaging scans to document disease progression or recurrence. The finding of new lesions always presents the challenge of differentiating between post-surgical changes, radiation necrosis, gliosis, and tumor, submitting these patients to more aggressive therapy and more toxicity. We reviewed the medical records of three patients with primary central nervous system tumors treated at the Children’s Hospital Los Angeles who had new false-positive magnetic resonance imaging findings suggestive of tumor recurrence. All of them had complete total resection of primary tumor, had received involved-field radiation therapy, had biopsies confirming absence of viable tumor, and all three patients are long-term survivors. These cases exemplify that not everything that enhances on brain or spine magnetic resonance imaging is viable tumor, and a biopsy should always be considered in the decision-making process in evaluation of potentially recurrent central nervous system tumors in pediatric patients. A step-wise approach for such challenging cases is presented in this article. PMID:27621807

  10. False positives in a reporter gene assay: identification and synthesis of substituted N-pyridin-2-ylbenzamides as competitive inhibitors of firefly luciferase.

    PubMed

    Heitman, Laura H; van Veldhoven, Jacobus P D; Zweemer, Annelien M; Ye, Kai; Brussee, Johannes; IJzerman, Adriaan P

    2008-08-14

    Luciferase reporter-gene assays are a commonly used technique in high-throughput screening campaigns. In this study, we report on a luciferase inhibitor (1), which emerged from an antagonistic G protein-coupled receptor luciferase reporter-gene assay screen. Instead of displaying receptor activity, compound 1 was shown to potently inhibit luciferase in an in vitro enzymatic assay with an IC50 value of 1.7 +/- 0.1 microM. In addition, 1 was a competitive inhibitor with respect to the substrate luciferin. A database search yielded another inhibitor (3) with a similar N-pyridin-2-ylbenzamide core. Subsequently, several analogues were prepared to investigate the structure-activity relationships of these luciferase inhibitors. This yielded the most potent inhibitor of this series (6) with an IC50 value of 0.069 +/- 0.01 microM. Further molecular modeling studies suggested that 6 can be accommodated in the luciferin binding site. This paper is meant to alert users of luciferase reporter-gene assays for possible false positive hits including highly "druglike" molecules due to direct luciferase inhibition.

  11. False-positive magnetic resonance imaging findings in follow-up of pediatric patients with tumors of the central nervous system.

    PubMed

    De Oliveira, Satiro Nakamura; Gonzalez-Gomez, Ignacio; Panigrahy, Ashok; Krieger, Mark; McComb, Gordon; Finlay, Jonathan L; Dhall, Girish

    2016-01-01

    Management of patients with central nervous system tumors relies largely on magnetic resonance imaging scans to document disease progression or recurrence. The finding of new lesions always presents the challenge of differentiating between post-surgical changes, radiation necrosis, gliosis, and tumor, submitting these patients to more aggressive therapy and more toxicity. We reviewed the medical records of three patients with primary central nervous system tumors treated at the Children's Hospital Los Angeles who had new false-positive magnetic resonance imaging findings suggestive of tumor recurrence. All of them had complete total resection of primary tumor, had received involved-field radiation therapy, had biopsies confirming absence of viable tumor, and all three patients are long-term survivors. These cases exemplify that not everything that enhances on brain or spine magnetic resonance imaging is viable tumor, and a biopsy should always be considered in the decision-making process in evaluation of potentially recurrent central nervous system tumors in pediatric patients. A step-wise approach for such challenging cases is presented in this article. PMID:27621807

  12. False-positive magnetic resonance imaging findings in follow-up of pediatric patients with tumors of the central nervous system

    PubMed Central

    De Oliveira, Satiro Nakamura; Gonzalez-Gomez, Ignacio; Panigrahy, Ashok; Krieger, Mark; McComb, Gordon; Finlay, Jonathan L; Dhall, Girish

    2016-01-01

    Management of patients with central nervous system tumors relies largely on magnetic resonance imaging scans to document disease progression or recurrence. The finding of new lesions always presents the challenge of differentiating between post-surgical changes, radiation necrosis, gliosis, and tumor, submitting these patients to more aggressive therapy and more toxicity. We reviewed the medical records of three patients with primary central nervous system tumors treated at the Children’s Hospital Los Angeles who had new false-positive magnetic resonance imaging findings suggestive of tumor recurrence. All of them had complete total resection of primary tumor, had received involved-field radiation therapy, had biopsies confirming absence of viable tumor, and all three patients are long-term survivors. These cases exemplify that not everything that enhances on brain or spine magnetic resonance imaging is viable tumor, and a biopsy should always be considered in the decision-making process in evaluation of potentially recurrent central nervous system tumors in pediatric patients. A step-wise approach for such challenging cases is presented in this article.

  13. Mixture of expert 3D massive-training ANNs for reduction of multiple types of false positives in CAD for detection of polyps in CT colonography.

    PubMed

    Suzuki, Kenji; Yoshida, Hiroyuki; Näppi, Janne; Armato, Samuel G; Dachman, Abraham H

    2008-02-01

    One of the major challenges in computer-aided detection (CAD) of polyps in CT colonography (CTC) is the reduction of false-positive detections (FPs) without a concomitant reduction in sensitivity. A large number of FPs is likely to confound the radiologist's task of image interpretation, lower the radiologist's efficiency, and cause radiologists to lose their confidence in CAD as a useful tool. Major sources of FPs generated by CAD schemes include haustral folds, residual stool, rectal tubes, the ileocecal valve, and extra-colonic structures such as the small bowel and stomach. Our purpose in this study was to develop a method for the removal of various types of FPs in CAD of polyps while maintaining a high sensitivity. To achieve this, we developed a "mixture of expert" three-dimensional (3D) massive-training artificial neural networks (MTANNs) consisting of four 3D MTANNs that were designed to differentiate between polyps and four categories of FPs: (1) rectal tubes, (2) stool with bubbles, (3) colonic walls with haustral folds, and (4) solid stool. Each expert 3D MTANN was trained with examples from a specific non-polyp category along with typical polyps. The four expert 3D MTANNs were combined with a mixing artificial neural network (ANN) such that different types of FPs could be removed. Our database consisted of 146 CTC datasets obtained from 73 patients whose colons were prepared by standard pre-colonoscopy cleansing. Each patient was scanned in both supine and prone positions. Radiologists established the locations of polyps through the use of optical-colonoscopy reports. Fifteen patients had 28 polyps, 15 of which were 5-9 mm and 13 were 10-25 mm in size. The CTC cases were subjected to our previously reported CAD method consisting of centerline-based extraction of the colon, shape-based detection of polyp candidates, and a Bayesian-ANN-based classification of polyps. The original CAD method yielded 96.4% (27/28) by-polyp sensitivity with an average of 3

  14. The false-positive responses of analgesic drugs to the intradermal serotonin- and compound 48/80-induced scratches as an animal model of itch.

    PubMed

    Ilkaya, Fatih; Yesilyurt, Ozgur; Seyrek, Melik; Gunduz, Ozgur; Ide, Tayfun; Akar, Ahmet; Ulugol, Ahmet; Guzel, Hasan; Dogrul, Ahmet; Ucar, Durmus; Gunaydin, Caner

    2016-01-01

    Intradermal injection of pruritogens such as serotonin, histamine and compound 48/80 into the skin and then, the evaluation of the scratching behavior is the commonly used animal model to advance pruritic research and drug development. However, predictive validity of this model is poorly documented. There is a close interaction between itch and pain sensations with regard to mediation through an anatomically and functionally identical neuronal pathway. One approach is whether the existing animal model of itch differentiates itch or pain to show efficacy of clinically effective analgesic drugs as a back translation. In this study, we explored the effects of different group of analgesic drugs on serotonin and compound 48/80-induced scratching behavior in Balb-C mice. Serotonin (25 μg) and compound 48/80 (100 μg) was injected intradermally in a volume of 50 μl into the rostral part of skin on the back of male mice and scratches were counted for a 30-min observation period. Morphine (1, 3, 10 mg/kg), tramadol (20, 40, 80 mg/kg), cannabinoid agonist CP 55,940 (0.1, 0.3, 1 mg/kg), paracetamol (100, 200, 300 mg/kg) and diclofenac (50, 100, 200 mg/kg) were given intraperitoneally 30 min prior to pruritogen injection. The analgesic drugs dose dependently blocked serotonin and compound 48/80-induced straching behavior with exerting complete inhibition at certain doses. Our data suggests that intradermal pruritogen-induced scratching models may not discriminate pain and itch sensations and give false positive results when standard analgesic drugs are used. PMID:27685776

  15. Use of parallel validation high-throughput screens to reduce false positives and identify novel dengue NS2B-NS3 protease inhibitors†

    PubMed Central

    Tomlinson, Suzanne M.; Watowich, Stanley J.

    2011-01-01

    Dengue virus (DENV), a mosquito-borne member of the family Flaviviridae, is a significant global pathogen affecting primarily tropical and subtropical regions of the world and placing tremendous burden on the limited medical infrastructure that exists in many of the developing countries located within these regions. Recent outbreaks in developed countries, including Australia (Hanna et al., 2009), France (Laruche et al., 2010), Taiwan (Kuan et al., 2010), and the USA (CDC, 2010), lead many researchers to believe that continued emergence into more temperate latitudes is likely. A primary concern is that there are no approved vaccines or antiviral therapies to treat DENV infections. Since the viral NS2B-NS3 protease (DENV NS2B-NS3pro) is required for virus replication, it provides a strategic target for the development of antiviral drugs. In this study, proof-of-concept high-throughput screenings (HTSs) were performed to unambiguously identify dengue 2 virus (DEN2V) NS2B-NS3pro inhibitors from a library of 2000 compounds. Validation screens were performed in parallel to concurrently eliminate insoluble, auto-fluorescing, and/or nonspecific inhibitors. Kinetic analyses of the hits revealed that parallel substrate fluorophore (AMC) interference controls and trypsin inhibition controls were able to reduce false positive rates due to solubility and fluorophore interference while the trypsin inhibition control additionally eliminated non-specific inhibitors. We identified five DEN2V NS2B-NS3pro inhibitors that also inhibited the related West Nile virus (WNV) protease (NS2B-NS3pro), but did not inhibit the trypsin protease. Biochemical analyses revealed various mechanisms of inhibition including competitive and mixed noncompetitive inhibition, with the lowest Ki values being 12 ± 1.5 μM for DEN2V NS2B-NS3pro and 2 ± 0.2 μM for WNV NS2B-NS3pro. PMID:22193283

  16. Contamination in the Kepler field. Identification of 685 KOIs as false positives via ephemeris matching based ON Q1-Q12 data

    SciTech Connect

    Coughlin, Jeffrey L.; Thompson, Susan E.; Burke, Christopher J.; Caldwell, Douglas A.; Jenkins, Jon M.; Mullally, Fergal R.; Rowe, Jason F.; Bryson, Stephen T.; Haas, Michael R.; Howell, Steve B.; Kolodziejczak, Jeffery J.

    2014-05-01

    The Kepler mission has to date found almost 6000 planetary transit-like signals, utilizing three years of data for over 170,000 stars at extremely high photometric precision. Due to its design, contamination from eclipsing binaries, variable stars, and other transiting planets results in a significant number of these signals being false positives (FPs). This directly affects the determination of the occurrence rate of Earth-like planets in our Galaxy, as well as other planet population statistics. In order to detect as many of these FPs as possible, we perform ephemeris matching among all transiting planet, eclipsing binary, and variable star sources. We find that 685 Kepler Objects of Interest (KOIs)—12% of all those analyzed—are FPs as a result of contamination, due to 409 unique parent sources. Of these, 118 have not previously been identified by other methods. We estimate that ∼35% of KOIs are FPs due to contamination, when performing a first-order correction for observational bias. Comparing single-planet candidate KOIs to multi-planet candidate KOIs, we find an observed FP fraction due to contamination of 16% and 2.4% respectively, bolstering the existing evidence that multi-planet KOIs are significantly less likely to be FPs. We also analyze the parameter distributions of the ephemeris matches and derive a simple model for the most common type of contamination in the Kepler field. We find that the ephemeris matching technique is able to identify low signal-to-noise FPs that are difficult to identify with other vetting techniques. We expect FP KOIs to become more frequent when analyzing more quarters of Kepler data, and note that many of them will not be able to be identified based on Kepler data alone.

  17. Curved planar reformation and optimal path tracing (CROP) method for false positive reduction in computer-aided detection of pulmonary embolism in CTPA

    NASA Astrophysics Data System (ADS)

    Zhou, Chuan; Chan, Heang-Ping; Guo, Yanhui; Wei, Jun; Chughtai, Aamer; Hadjiiski, Lubomir M.; Sundaram, Baskaran; Patel, Smita; Kuriakose, Jean W.; Kazerooni, Ella A.

    2013-03-01

    The curved planar reformation (CPR) method re-samples the vascular structures along the vessel centerline to generate longitudinal cross-section views. The CPR technique has been commonly used in coronary CTA workstation to facilitate radiologists' visual assessment of coronary diseases, but has not yet been used for pulmonary vessel analysis in CTPA due to the complicated tree structures and the vast network of pulmonary vasculature. In this study, a new curved planar reformation and optimal path tracing (CROP) method was developed to facilitate feature extraction and false positive (FP) reduction and improve our PE detection system. PE candidates are first identified in the segmented pulmonary vessels at prescreening. Based on Dijkstra's algorithm, the optimal path (OP) is traced from the pulmonary trunk bifurcation point to each PE candidate. The traced vessel is then straightened and a reformatted volume is generated using CPR. Eleven new features that characterize the intensity, gradient, and topology are extracted from the PE candidate in the CPR volume and combined with the previously developed 9 features to form a new feature space for FP classification. With IRB approval, CTPA of 59 PE cases were retrospectively collected from our patient files (UM set) and 69 PE cases from the PIOPED II data set with access permission. 595 and 800 PEs were manually marked by experienced radiologists as reference standard for the UM and PIOPED set, respectively. At a test sensitivity of 80%, the average FP rate was improved from 18.9 to 11.9 FPs/case with the new method for the PIOPED set when the UM set was used for training. The FP rate was improved from 22.6 to 14.2 FPs/case for the UM set when the PIOPED set was used for training. The improvement in the free response receiver operating characteristic (FROC) curves was statistically significant (p<0.05) by JAFROC analysis, indicating that the new features extracted from the CROP method are useful for FP reduction.

  18. False-positive antibody signals for the pluripotency factor OCT4A (POU5F1) in testis-derived cells may lead to erroneous data and misinterpretations.

    PubMed

    Warthemann, R; Eildermann, K; Debowski, K; Behr, R

    2012-12-01

    Octamer-binding protein 4 (OCT4) is a key player in pluripotent embryonic stem (ES) cells and is essential for the generation of induced pluripotent stem cells. Recently, several reports indicated the spontaneous recovery of pluripotency in cultured adult human testis-derived cells. This was evidenced also by the detection of OCT4 using antibodies. However, the soundness of some data was recently put into question. During our attempts to derive pluripotent cells from the common marmoset monkey (Callithrix jacchus) testis, we obtained inconsistent data which prompted us to analyze deeper the characteristics of three independent OCT4 antibodies that were used in numerous published studies that received greatest attention. All antibodies detected OCT4 by immunofluorescence (IF) in a marmoset monkey ES cell line. Two of the three OCT4 antibodies also gave robust nuclear signals in testis-derived cells. However, the latter cells expressed no OCT4 mRNA as revealed by quantitative RT-PCR and turned out to be mesenchymal cells. When tested in western blot analyses, all antibodies detected heterologously expressed marmoset monkey OCT4 protein. But, importantly, those antibodies that resulted in non-specific signals in IF also showed additional non-specific bands in western blots. In summary, some commercially available OCT4 antibodies result in false-positive signals which may provoke erroneous conclusions when used in studies aiming at the generation of pluripotent cells in vitro. We conclude that (i) antibodies must be carefully characterized before use to prevent misleading observations and (ii) OCT4 expression must be monitored by a second antibody-independent method.

  19. Frequency of False Positive Rapid HIV Serologic Tests in African Men and Women Receiving PrEP for HIV Prevention: Implications for Programmatic Roll-Out of Biomedical Interventions

    PubMed Central

    Ndase, Patrick; Celum, Connie; Kidoguchi, Lara; Ronald, Allan; Fife, Kenneth H.; Bukusi, Elizabeth; Donnell, Deborah; Baeten, Jared M.

    2015-01-01

    Background Rapid HIV assays are the mainstay of HIV testing globally. Delivery of effective biomedical HIV prevention strategies such as antiretroviral pre-exposure prophylaxis (PrEP) requires periodic HIV testing. Because rapid tests have high (>95%) but imperfect specificity, they are expected to generate some false positive results. Methods We assessed the frequency of true and false positive rapid results in the Partners PrEP Study, a randomized, placebo-controlled trial of PrEP. HIV testing was performed monthly using 2 rapid tests done in parallel with HIV enzyme immunoassay (EIA) confirmation following all positive rapid tests. Results A total of 99,009 monthly HIV tests were performed; 98,743 (99.7%) were dual-rapid HIV negative. Of the 266 visits with ≥1 positive rapid result, 99 (37.2%) had confirmatory positive EIA results (true positives), 155 (58.3%) had negative EIA results (false positives), and 12 (4.5%) had discordant EIA results. In the active PrEP arms, over two-thirds of visits with positive rapid test results were false positive results (69.2%, 110 of 159), although false positive results occurred at <1% (110/65,945) of total visits. Conclusions When HIV prevalence or incidence is low due to effective HIV prevention interventions, rapid HIV tests result in a high number of false relative to true positive results, although the absolute number of false results will be low. Program roll-out for effective interventions should plan for quality assurance of HIV testing, mechanisms for confirmatory HIV testing, and counseling strategies for persons with positive rapid test results. PMID:25885664

  20. Positive and negative stimuli in relation to tennis players' reaction time.

    PubMed

    Mead, T P; Drowatzky, J N; Hardin-Crosby, L

    2000-02-01

    Research has indicated that negative and positive thoughts may affect sport performance. The purpose of this analogue study was to assess whether negative and positive stimuli influenced tennis performance similar to positive and negative thought. The reaction time (RT) of 40 competitive tennis players was measured during a timed response to a tennis ball rotating in a topspin, sidespin, or backspin direction on the computer screen. Immediately prior to the ball presentation, a phrase (accessory stimulus) was presented visually or aurally. The accessory stimulus provided either positive (e.g., 'nice shot') or negative information (e.g., 'bad shot') followed by the subject's name. Analysis showed a main effect only for the type of spin. The slowest RT occurred when responding to a tennis ball rotating in a backspin direction. A significant interaction was found for the sensory modality (audition vs vision) and polarity (positive vs negative) of the accessory stimulus. RT to negative stimuli was slowest when the accessory stimulus was presented aurally. The quickest RT to positive stimuli occurred when the accessory stimulus was presented aurally. These results indicated that negative and positive stimuli, when presented aurally, affected performance as positive and negative thoughts measured in other studies. Not measured was whether negative and positive stimuli actually produce the negative and positive thoughts, respectively, that have been reported to affect performance.

  1. Positive and negative stimuli in relation to tennis players' reaction time.

    PubMed

    Mead, T P; Drowatzky, J N; Hardin-Crosby, L

    2000-02-01

    Research has indicated that negative and positive thoughts may affect sport performance. The purpose of this analogue study was to assess whether negative and positive stimuli influenced tennis performance similar to positive and negative thought. The reaction time (RT) of 40 competitive tennis players was measured during a timed response to a tennis ball rotating in a topspin, sidespin, or backspin direction on the computer screen. Immediately prior to the ball presentation, a phrase (accessory stimulus) was presented visually or aurally. The accessory stimulus provided either positive (e.g., 'nice shot') or negative information (e.g., 'bad shot') followed by the subject's name. Analysis showed a main effect only for the type of spin. The slowest RT occurred when responding to a tennis ball rotating in a backspin direction. A significant interaction was found for the sensory modality (audition vs vision) and polarity (positive vs negative) of the accessory stimulus. RT to negative stimuli was slowest when the accessory stimulus was presented aurally. The quickest RT to positive stimuli occurred when the accessory stimulus was presented aurally. These results indicated that negative and positive stimuli, when presented aurally, affected performance as positive and negative thoughts measured in other studies. Not measured was whether negative and positive stimuli actually produce the negative and positive thoughts, respectively, that have been reported to affect performance. PMID:10769904

  2. Angular Dependency and Kinematics of Light Atom Nuclear Reactions with Positive Q Values

    NASA Astrophysics Data System (ADS)

    Pacheco, Jose; Naab, Fabian; Marble, Daniel; Duggan, Jerome

    2006-10-01

    Einstein's relationship, E=mĉ2 implies that energy can be changed into mass and vice versa. Using nuclear reaction analysis, the interchange of mass into energy can be used to analyze trace elements in a material since each given element has a set of nuclear reactions that are unique to it. These nuclear reactions have positive Q values, which show up as excess energy in the emitted particle spectrum. However accurate interpretation of these spectra for materials analysis can be complicated as knowledge of both the angular dependency of the reaction and the geometry of the detection setup is required. The angular dependence is usually easily taken into account provided the reaction is well known and there are no nuclear interferences. In this experiment, a 1 MeV proton beam from a 2.5 MeV Van De Graff was applied to targets made up of light atoms, mainly 7Li, 6Li, and 19F. The results demonstrate the importance of accurately knowing the detection configuration, geometry, and the effect of detection system resolution when doing NRA. For instance, our system failed to give any information about the nuclear reaction for angles less than 30 degrees from the incoming beam due to its resolution.

  3. Two cases of false-positive dengue non-structural protein 1 (NS1) antigen in patients with hematological malignancies and a review of the literature on the use of NS1 for the detection of Dengue infection.

    PubMed

    Chung, Shimin J; Krishnan, Prabha U; Leo, Yee Sin

    2015-02-01

    Early diagnosis of dengue has been made easier in recent years owing to the advancement in diagnostic technologies. The rapid non-structural protein 1 (NS1) test strip is widely used in many developed and developing regions at risk of dengue. Despite the relatively high specificity of this test, we recently encountered two cases of false-positive dengue NS1 antigen in patients with underlying hematological malignancies. We reviewed the literature for causes of false-positive dengue NS1.

  4. Position-specific isotope modeling of organic micropollutants transformation through different reaction pathways.

    PubMed

    Jin, Biao; Rolle, Massimo

    2016-03-01

    The degradation of organic micropollutants occurs via different reaction pathways. Compound specific isotope analysis is a valuable tool to identify such degradation pathways in different environmental systems. We propose a mechanism-based modeling approach that provides a quantitative framework to simultaneously evaluate concentration as well as bulk and position-specific multi-element isotope evolution during the transformation of organic micropollutants. The model explicitly simulates position-specific isotopologues for those atoms that experience isotope effects and, thereby, provides a mechanistic description of isotope fractionation occurring at different molecular positions. To demonstrate specific features of the modeling approach, we simulated the degradation of three selected organic micropollutants: dichlorobenzamide (BAM), isoproturon (IPU) and diclofenac (DCF). The model accurately reproduces the multi-element isotope data observed in previous experimental studies. Furthermore, it precisely captures the dual element isotope trends characteristic of different reaction pathways as well as their range of variation consistent with observed bulk isotope fractionation. It was also possible to directly validate the model capability to predict the evolution of position-specific isotope ratios with available experimental data. Therefore, the approach is useful both for a mechanism-based evaluation of experimental results and as a tool to explore transformation pathways in scenarios for which position-specific isotope data are not yet available.

  5. Position-specific isotope modeling of organic micropollutants transformation through different reaction pathways.

    PubMed

    Jin, Biao; Rolle, Massimo

    2016-03-01

    The degradation of organic micropollutants occurs via different reaction pathways. Compound specific isotope analysis is a valuable tool to identify such degradation pathways in different environmental systems. We propose a mechanism-based modeling approach that provides a quantitative framework to simultaneously evaluate concentration as well as bulk and position-specific multi-element isotope evolution during the transformation of organic micropollutants. The model explicitly simulates position-specific isotopologues for those atoms that experience isotope effects and, thereby, provides a mechanistic description of isotope fractionation occurring at different molecular positions. To demonstrate specific features of the modeling approach, we simulated the degradation of three selected organic micropollutants: dichlorobenzamide (BAM), isoproturon (IPU) and diclofenac (DCF). The model accurately reproduces the multi-element isotope data observed in previous experimental studies. Furthermore, it precisely captures the dual element isotope trends characteristic of different reaction pathways as well as their range of variation consistent with observed bulk isotope fractionation. It was also possible to directly validate the model capability to predict the evolution of position-specific isotope ratios with available experimental data. Therefore, the approach is useful both for a mechanism-based evaluation of experimental results and as a tool to explore transformation pathways in scenarios for which position-specific isotope data are not yet available. PMID:26708763

  6. Abiotic production of nitrous oxide by lightning. Implications for a false positive identification of life on Earth-Like Planets around quiescent M Dwarfs

    NASA Astrophysics Data System (ADS)

    Navarro, Karina F.; Navarro-Gonzalez, Rafael; McKay, Christopher P.

    _{2} dominated primitive Earth-like atmospheres. However, during the rise in atmospheric O _{2} at the start of the Proterozoic, the ocean became stratified (anoxic at the bottom and oxygenic at the surface). During this period, the emissions of N _{2}O were probably higher than today associated with a stronger microbial activity in the early anoxic ocean layer (Grenfell et al., 2011). Under this scenario, the predicted N _{2}O concentration would be about 3920 ppb, considering 10% the current atmospheric O _{2} concentrations, 100 times higher the current microbial N _{2}O flux, and a fainter Sun (94.3%) (Grenfell et al., 2011). This concentration would be still undetectable (Grenfell et al., 2011). A completely different scenario could be expected in Earth-like planets orbiting M dwarfs, which are the most abundant stars in the galaxy, representing about 75% of the total stellar population. M stars exhibit a large range in activity levels from very low levels of chromospheric and coronal activity, the so-called “quiescent” to high levels, the so-called “active" states. Photochemical models predict that the N _{2}O concentration would only increase to about 1,000 ppb for the current Earth orbiting an active M star, but surprisingly up to about 1,000 ppm for the current Earth orbiting a quiescent M star (Segura et al., 2005). Therefore, N _{2}O becomes a promising biomarker. Under this scenario it is important to constrain the abiotic sources of N _{2}O under different atmospheric conditions to avoid a false positive identification of life. Here we report an experimental study of the effects of lightning discharges on the nitrogen fixation rate during the evolution of the Earth’s early atmosphere from 10 to 1 percent of carbon dioxide in molecular nitrogen. We extended our study from no methane up to 1,000 ppm CH _{4}, which would be applicable to the postbiotic Earth (Tian et al., 2011). Lightning was simulated in the laboratory by a plasma generated with a

  7. High level of HIV-2 false positivity in KwaZulu-Natal province: a region of South Africa with a very high HIV-1 subtype C prevalence.

    PubMed

    Singh, Lavanya; Parboosing, Raveen; Manasa, Justen; Moodley, Pravi; de Oliveira, Tulio

    2013-12-01

    Human immunodeficiency virus 2 (HIV-2) is found predominantly in West Africa. It is not unlikely, however, that HIV-2 may also be found in South Africa, due to the influx of immigrants into this country. It is important to distinguish between HIV-1 and HIV-2 since the clinical courses and treatment responses of these viruses are different. Routine serological methods for diagnosing HIV do not differentiate between HIV-1 and -2 infections, while rapid tests, viral load quantification and PCR are HIV-type--specific. The objective of this study was to describe the seroprevalence and molecular epidemiology of HIV-2 in KwaZulu-Natal, one of the regions with the highest HIV prevalence in the world and home of the two largest harbors in South Africa. HIV-1 positive samples were screened for antibodies against HIV-2, using a rapid test. The confirmation of HIV-2 positive samples was done by PCR. Of the 2,123 samples screened, 319 (15%) were identified as positive by the rapid test. None of these samples were confirmed positive by PCR. To explore this discrepancy in the results, a subset (n = 52) of the rapid HIV-2 positive samples was subjected to Western blotting. Thirty-seven (71%) of these were positive, yielding an overall HIV-2 seroprevalence of 10.6%. Three out of 28 (10.7%) Western blot positive samples were positive by a Pepti-LAV assay. This discrepancy between serological and molecular confirmation may be attributed to non-specific or cross-reacting antibodies. The use of rapid tests and Western blots for HIV-2 diagnosis in South Africa should be interpreted with caution.

  8. Space positional and motion SRC effects: A comparison with the use of reaction time distribution analysis

    PubMed Central

    Styrkowiec, Piotr; Szczepanowski, Remigiusz

    2013-01-01

    The analysis of reaction time (RT) distributions has become a recognized standard in studies on the stimulus response correspondence (SRC) effect as it allows exploring how this effect changes as a function of response speed. In this study, we compared the spatial SRC effect (the classic Simon effect) with the motion SRC effect using RT distribution analysis. Four experiments were conducted, in which we manipulated factors of space position and motion for stimulus and response, in order to obtain a clear distinction between positional SRC and motion SRC. Results showed that these two types of SRC effects differ in their RT distribution functions as the space positional SRC effect showed a decreasing function, while the motion SRC showed an increasing function. This suggests that different types of codes underlie these two SRC effects. Potential mechanisms and processes are discussed. PMID:24605178

  9. Abiotic production of nitrous oxide by lightning. Implications for a false positive identification of life on Earth-Like Planets around quiescent M Dwarfs

    NASA Astrophysics Data System (ADS)

    Navarro, Karina F.; Navarro-Gonzalez, Rafael; McKay, Christopher P.

    _{2} dominated primitive Earth-like atmospheres. However, during the rise in atmospheric O _{2} at the start of the Proterozoic, the ocean became stratified (anoxic at the bottom and oxygenic at the surface). During this period, the emissions of N _{2}O were probably higher than today associated with a stronger microbial activity in the early anoxic ocean layer (Grenfell et al., 2011). Under this scenario, the predicted N _{2}O concentration would be about 3920 ppb, considering 10% the current atmospheric O _{2} concentrations, 100 times higher the current microbial N _{2}O flux, and a fainter Sun (94.3%) (Grenfell et al., 2011). This concentration would be still undetectable (Grenfell et al., 2011). A completely different scenario could be expected in Earth-like planets orbiting M dwarfs, which are the most abundant stars in the galaxy, representing about 75% of the total stellar population. M stars exhibit a large range in activity levels from very low levels of chromospheric and coronal activity, the so-called “quiescent” to high levels, the so-called “active" states. Photochemical models predict that the N _{2}O concentration would only increase to about 1,000 ppb for the current Earth orbiting an active M star, but surprisingly up to about 1,000 ppm for the current Earth orbiting a quiescent M star (Segura et al., 2005). Therefore, N _{2}O becomes a promising biomarker. Under this scenario it is important to constrain the abiotic sources of N _{2}O under different atmospheric conditions to avoid a false positive identification of life. Here we report an experimental study of the effects of lightning discharges on the nitrogen fixation rate during the evolution of the Earth’s early atmosphere from 10 to 1 percent of carbon dioxide in molecular nitrogen. We extended our study from no methane up to 1,000 ppm CH _{4}, which would be applicable to the postbiotic Earth (Tian et al., 2011). Lightning was simulated in the laboratory by a plasma generated with a

  10. Positional assembly of enzymes on bacterial outer membrane vesicles for cascade reactions.

    PubMed

    Park, Miso; Sun, Qing; Liu, Fang; DeLisa, Matthew P; Chen, Wilfred

    2014-01-01

    The systematic organization of enzymes is a key feature for the efficient operation of cascade reactions in nature. Here, we demonstrate a facile method to create nanoscale enzyme cascades by using engineered bacterial outer membrane vesicles (OMVs) that are spheroid nanoparticles (roughly 50 nm in diameter) produced by Gram-negative bacteria during all phases of growth. By taking advantage of the fact that OMVs naturally contain proteins found in the outer cell membrane, we displayed a trivalent protein scaffold containing three divergent cohesin domains for the position-specific presentation of a three-enzyme cascade on OMVs through a truncated ice nucleation protein anchoring motif (INP). The positional assembly of three enzymes for cellulose hydrolysis was demonstrated. The enzyme-decorated OMVs provided synergistic cellulose hydrolysis resulting in 23-fold enhancement in glucose production than free enzymes. PMID:24820175

  11. A case of disseminated histoplasmosis following autologous stem cell transplantation for Hodgkin's lymphoma: an initial misdiagnosis with a false-positive serum galactomannan assay.

    PubMed

    Jones, O; Cleveland, K O; Gelfand, M S

    2009-06-01

    Systemic histoplasmosis is uncommonly reported in patients who have undergone bone marrow or solid organ transplantation. Diagnosis of systemic histoplasmosis in recipients of transplants may be hampered by lack of consideration of this infection in the differential diagnosis and may be confounded by conflicting information from other testing performed to evaluate for opportunistic infections in this population. We report successful treatment of a case of disseminated histoplasmosis in a patient with Hodgkin's lymphoma who had undergone autologous stem cell transplantation. The diagnosis was delayed by the finding of a positive serum galactomannan assay. PMID:19302274

  12. MARVELS-1: A FACE-ON DOUBLE-LINED BINARY STAR MASQUERADING AS A RESONANT PLANETARY SYSTEM AND CONSIDERATION OF RARE FALSE POSITIVES IN RADIAL VELOCITY PLANET SEARCHES

    SciTech Connect

    Wright, Jason T.; Roy, Arpita; Mahadevan, Suvrath; Wang, Sharon X.; Fleming, Scott W.; Ford, Eric B.; Payne, Matt; Lee, Brian L.; Ge, Jian; Wang, Ji; Crepp, Justin R.; Gaudi, B. Scott; Eastman, Jason; Pepper, Joshua; Cargile, Phillip; Stassun, Keivan G.; Ghezzi, Luan; Gonzalez-Hernandez, Jonay I.; Wisniewski, John; Dutra-Ferreira, Leticia; and others

    2013-06-20

    We have analyzed new and previously published radial velocity (RV) observations of MARVELS-1, known to have an ostensibly substellar companion in a {approx}6 day orbit. We find significant ({approx}100 m s{sup -1}) residuals to the best-fit model for the companion, and these residuals are naievely consistent with an interior giant planet with a P = 1.965 days in a nearly perfect 3:1 period commensurability (|P{sub b} /P{sub c} - 3| < 10{sup -4}). We have performed several tests for the reality of such a companion, including a dynamical analysis, a search for photometric variability, and a hunt for contaminating stellar spectra. We find many reasons to be critical of a planetary interpretation, including the fact that most of the three-body dynamical solutions are unstable. We find no evidence for transits, and no evidence of stellar photometric variability. We have discovered two apparent companions to MARVELS-1 with adaptive optics imaging at Keck; both are M dwarfs, one is likely bound, and the other is likely a foreground object. We explore false-alarm scenarios inspired by various curiosities in the data. Ultimately, a line profile and bisector analysis lead us to conclude that the {approx}100 m s{sup -1} residuals are an artifact of spectral contamination from a stellar companion contributing {approx}15%-30% of the optical light in the system. We conclude that origin of this contamination is the previously detected RV companion to MARVELS-1, which is not, as previously reported, a brown dwarf, but in fact a G dwarf in a face-on orbit.

  13. Experimental Correlation of Substrate Position with Reaction Outcome in the Aliphatic Halogenase, SyrB2

    PubMed Central

    Martinie, Ryan J.; Livada, Jovan; Chang, Wei-chen; Green, Michael T.; Krebs, Carsten; Bollinger, J. Martin; Silakov, Alexey

    2015-01-01

    The iron(II)- and 2-(oxo)glutarate-dependent (Fe/2OG) oxygenases catalyze an array of challenging transformations, but how individual members of the enzyme family direct different outcomes is poorly understood. The Fe/2OG halogenase, SyrB2, chlorinates C4 of its native substrate, L-threonine appended to the carrier protein, SyrB1, but hydroxylates C5 of L-norvaline and, to a lesser extent, C4 of L-aminobutyric acid when SyrB1 presents these non-native amino acids. To test the hypothesis that positioning of the targeted carbon dictates the outcome, we defined the positions of these three substrates by measuring hyperfine couplings between substrate deuterium atoms and the stable, EPR-active iron-nitrosyl adduct, a surrogate for reaction intermediates. The Fe-2H distances and N-Fe-2H angles, which vary from 4.2 Å and 85° for threonine to 3.4 Å and 65° for norvaline, rationalize the trends in reactivity. This experimental correlation of position to outcome should aid in judging from structural data on other Fe/2OG enzymes whether they suppress hydroxylation or form hydroxylated intermediates on the pathways to other outcomes. PMID:25965587

  14. Position-specific isotope modeling of organic micropollutants transformations through different reaction pathways

    NASA Astrophysics Data System (ADS)

    Jin, Biao; Rolle, Massimo

    2016-04-01

    Organic compounds are produced in vast quantities for industrial and agricultural use, as well as for human and animal healthcare [1]. These chemicals and their metabolites are frequently detected at trace levels in fresh water environments where they undergo degradation via different reaction pathways. Compound specific stable isotope analysis (CSIA) is a valuable tool to identify such degradation pathways in different environmental systems. Recent advances in analytical techniques have promoted the fast development and implementation of multi-element CSIA. However, quantitative frameworks to evaluate multi-element stable isotope data and incorporating mechanistic information on the degradation processes [2,3] are still lacking. In this study we propose a mechanism-based modeling approach to simultaneously evaluate concentration as well as bulk and position-specific multi-element isotope evolution during the transformation of organic micropollutants. The model explicitly simulates position-specific isotopologues for those atoms that experience isotope effects and, thereby, provides a mechanistic description of isotope fractionation occurring at different molecular positions. We validate the proposed approach with the concentration and multi-element isotope data of three selected organic micropollutants: dichlorobenzamide (BAM), isoproturon (IPU) and diclofenac (DCF). The model precisely captures the dual element isotope trends characteristic of different reaction pathways and their range of variation consistent with observed multi-element (C, N) bulk isotope fractionation. The proposed approach can also be used as a tool to explore transformation pathways in scenarios for which position-specific isotope data are not yet available. [1] Schwarzenbach, R.P., Egli, T., Hofstetter, T.B., von Gunten, U., Wehrli, B., 2010. Global Water Pollution and Human Health. Annu. Rev. Environ. Resour. doi:10.1146/annurev-environ-100809-125342. [2] Jin, B., Haderlein, S.B., Rolle, M

  15. Relevance of semen polymerase chain reaction positive for tuberculosis in asymptomatic men undergoing infertility evaluation

    PubMed Central

    Regmi, Subodh Kumar; Singh, Urvashi B.; Sharma, Jai Bhagwan; Kumar, Rajeev

    2015-01-01

    OBJECTIVE: Male partners of infertile women with genital tuberculosis (TB) are often screened for genital TB. We aimed to evaluate the clinical significance of a positive screening semen polymerase chain reaction (PCR) for Mycobacterium tuberculosis test (TB-PCR) in asymptomatic men undergoing infertility evaluation and determine the need for a detailed investigation and treatment for TB. MATERIALS AND METHODS: Between March 2012 and January 2013, male partners of 15 infertile women with a diagnosis of genitourinary TB (GUTB) as the cause of infertility, tested positive either on semen PCR for TB (13 cases), or Mycobacterium Growth Indicator Tube-960 test (2 cases). These asymptomatic men underwent infertility evaluation along with evaluation for GUTB. Diagnosis of GUTB was based on standard clinical criteria, which included a high index of suspicion along with clinical, laboratory, and/or radiological evidence of GUTB. Men who had no clinical evidence of GUTB were followed up with clinical evaluation, semen analysis, and repeat semen PCR for TB after 6 months. RESULTS: Fourteen subjects consented for inclusion in the study. One had a history of pulmonary TB 20 years earlier. Another patient was found to have mediastinal lymphadenopathy (tubercular). All except one had a normal semen analysis. None of the patients met the standard clinical criteria for GUTB diagnosis. 8 patients followed up at 6 months with repeat semen analysis, which was similar to the baseline values and no clinical evidence of TB. INTERPRETATION AND CONCLUSIONS: Asymptomatic men with positive screening semen PCR for TB do not have clinical evidence of TB. Male partners of women with infertility and GUTB should not be screened if they have no symptoms. PMID:26538860

  16. HAMS: High-Affinity Mass Spectrometry Screening. A High-Throughput Screening Method for Identifying the Tightest-Binding Lead Compounds for Target Proteins with No False Positive Identifications

    NASA Astrophysics Data System (ADS)

    Imaduwage, Kasun P.; Go, Eden P.; Zhu, Zhikai; Desaire, Heather

    2016-09-01

    A major challenge in drug discovery is the identification of high affinity lead compounds that bind a particular target protein; these leads are typically identified by high throughput screens. Mass spectrometry has become a detection method of choice in drug screening assays because the target and the ligand need not be modified. Label-free assays are advantageous because they can be developed more rapidly than assays requiring labels, and they eliminate the risk of the label interfering with the binding event. However, in commonly used MS-based screening methods, detection of false positives is a major challenge. Here, we describe a detection strategy designed to eliminate false positives. In this approach, the protein and the ligands are incubated together, and the non-binders are separated for detection. Hits (protein binders) are not detectable by MS after incubation with the protein, but readily identifiable by MS when the target protein is not present in the incubation media. The assay was demonstrated using three different proteins and hundreds of non-inhibitors; no false positive hits were identified in any experiment. The assay can be tuned to select for ligands of a particular binding affinity by varying the quantity of protein used and the immobilization method. As examples, the method selectively detected inhibitors that have Ki values of 0.2 μM, 50 pM, and 700 pM. These findings demonstrate that the approach described here compares favorably with traditional MS-based screening methods.

  17. HAMS: High-Affinity Mass Spectrometry Screening. A High-Throughput Screening Method for Identifying the Tightest-Binding Lead Compounds for Target Proteins with No False Positive Identifications

    NASA Astrophysics Data System (ADS)

    Imaduwage, Kasun P.; Go, Eden P.; Zhu, Zhikai; Desaire, Heather

    2016-11-01

    A major challenge in drug discovery is the identification of high affinity lead compounds that bind a particular target protein; these leads are typically identified by high throughput screens. Mass spectrometry has become a detection method of choice in drug screening assays because the target and the ligand need not be modified. Label-free assays are advantageous because they can be developed more rapidly than assays requiring labels, and they eliminate the risk of the label interfering with the binding event. However, in commonly used MS-based screening methods, detection of false positives is a major challenge. Here, we describe a detection strategy designed to eliminate false positives. In this approach, the protein and the ligands are incubated together, and the non-binders are separated for detection. Hits (protein binders) are not detectable by MS after incubation with the protein, but readily identifiable by MS when the target protein is not present in the incubation media. The assay was demonstrated using three different proteins and hundreds of non-inhibitors; no false positive hits were identified in any experiment. The assay can be tuned to select for ligands of a particular binding affinity by varying the quantity of protein used and the immobilization method. As examples, the method selectively detected inhibitors that have Ki values of 0.2 μM, 50 pM, and 700 pM. These findings demonstrate that the approach described here compares favorably with traditional MS-based screening methods.

  18. A positive response to an adverse reaction. Diagnosis and management of food intolerance in children.

    PubMed

    Holmes, S

    1993-04-01

    1. Food intolerance is a reproducible abnormal reaction to food or food components which is not psychologically based. 2. It is straightforward to identify immediate hypersensitivity, but delayed reactions (4-27 hours) are more difficult. 3. The main foods causing reactions are wheat, milk, chicken, eggs, fish and shellfish, but any food can cause a reaction in a sensitised individual. 4. The solution to the problem relies on identification of the causative food(s) and its total elimination from the diet.

  19. Modeling Kepler Transit Light Curves as False Positives: Rejection of Blend Scenarios for Kepler-9, and Validation of Kepler-9 d, a Super-Earth-Size Planet in a Multiple System

    NASA Technical Reports Server (NTRS)

    Torres, Guillermo; Fressin, Francois; Batalha, Natalie M.; Borucki, William J.; Brown, Timothy M.; Bryson, Stephen T.; Buchhave, Lars A.; Charbonneau, David; Ciardi, David R.; Dunham, Edward W.; Fabrycky, Daniel C.; Ford, Eric B.; Gauthier, Thomas N., III; Gilliland, Ronald L.; Holman, Matthew J.; Howell, Steve B.; Isaacson, Howard; Jenkins, Jon M.; Koch, David G.; Latham, David W.; Lissauer, Jack J.; Marcy, Geoffrey W.; Monet, David G.; Prsa, Andrej; Quinn, Samuel N.

    2011-01-01

    Light curves from the Kepler Mission contain valuable information on the nature of the phenomena producing the transit-like signals. To assist in exploring the possibility that they are due to an astrophysical false positive we describe a procedure (BLENDER) to model the photometry in terms of a blend rather than a planet orbiting a star. A blend may consist of a background or foreground eclipsing binary (or star-planet pair) whose eclipses are attenuated by the light of the candidate and possibly other stars within the photometric aperture. We apply BLENDER to the case of Kepler-9 (KIC 3323887), a target harboring two previously confirmed Saturn-size planets (Kepler-9 b and Kepler-9 c) showing transit timing variations, and an additional shallower signal with a 1.59 day period suggesting the presence of a super-Earth-size planet. Using BLENDER together with constraints from other follow-up observations we are able to rule out all blends for the two deeper signals and provide independent validation of their planetary nature. For the shallower signal, we rule out a large fraction of the false positives that might mimic the transits. The false alarm rate for remaining blends depends in part (and inversely) on the unknown frequency of small-size planets. Based on several realistic estimates of this frequency, we conclude with very high confidence that this small signal is due to a super-Earth-size planet (Kepler-9 d) in a multiple system, rather than a false positive. The radius is determined to be 1.64(exp)(sub-14),R, and current spectroscopic observations are as yet insufficient to establish its mass.

  20. MODELING KEPLER TRANSIT LIGHT CURVES AS FALSE POSITIVES: REJECTION OF BLEND SCENARIOS FOR KEPLER-9, AND VALIDATION OF KEPLER-9 d, A SUPER-EARTH-SIZE PLANET IN A MULTIPLE SYSTEM

    SciTech Connect

    Torres, Guillermo; Fressin, Francois; Charbonneau, David; Fabrycky, Daniel C.; Holman, Matthew J.; Latham, David W.; Batalha, Natalie M.; Borucki, William J.; Bryson, Stephen T.; Koch, David G.; Brown, Timothy M.; Buchhave, Lars A.; Ciardi, David R.; Ford, Eric B.; Gautier, Thomas N. III; Howell, Steve B.; Isaacson, Howard; Jenkins, Jon M.

    2011-01-20

    Light curves from the Kepler Mission contain valuable information on the nature of the phenomena producing the transit-like signals. To assist in exploring the possibility that they are due to an astrophysical false positive, we describe a procedure (BLENDER) to model the photometry in terms of a 'blend' rather than a planet orbiting a star. A blend may consist of a background or foreground eclipsing binary (or star-planet pair) whose eclipses are attenuated by the light of the candidate and possibly other stars within the photometric aperture. We apply BLENDER to the case of Kepler-9 (KIC 3323887), a target harboring two previously confirmed Saturn-size planets (Kepler-9 b and Kepler-9 c) showing transit timing variations, and an additional shallower signal with a 1.59 day period suggesting the presence of a super-Earth-size planet. Using BLENDER together with constraints from other follow-up observations we are able to rule out all blends for the two deeper signals and provide independent validation of their planetary nature. For the shallower signal, we rule out a large fraction of the false positives that might mimic the transits. The false alarm rate for remaining blends depends in part (and inversely) on the unknown frequency of small-size planets. Based on several realistic estimates of this frequency, we conclude with very high confidence that this small signal is due to a super-Earth-size planet (Kepler-9 d) in a multiple system, rather than a false positive. The radius is determined to be 1.64{sup +0.19}{sub -0.14} R{sub +}, and current spectroscopic observations are as yet insufficient to establish its mass.

  1. The Rapid Test Based on Leishmania infantum Chimeric rK28 Protein Improves the Diagnosis of Canine Visceral Leishmaniasis by Reducing the Detection of False-Positive Dogs.

    PubMed

    Fraga, Deborah Bittencourt Mothé; Pacheco, Luciano Vasconcellos; Borja, Lairton Souza; Tuy, Pétala Gardênia da Silva Estrela; Bastos, Leila Andrade; Solcà, Manuela da Silva; Amorim, Leila Denise Alves Ferreira; Veras, Patrícia Sampaio Tavares

    2016-01-01

    Visceral Leishmaniasis (VL) has spread to many urban centers worldwide. Dogs are considered the main reservoir of VL, because canine cases often precede the occurrence of human cases. Detection and euthanasia of serologically positive dogs is one of the primary VL control measures utilized in some countries, including Brazil. Using accurate diagnostic tests can minimize one undesirable consequence of this measure, culling false-positive dogs, and reduce the maintenance of false-negative dogs in endemic areas. In December 2011, the Brazilian Ministry of Health replaced the ELISA (EIE CVL) screening method and Indirect Immunofluorescence Test (IFI CVL) confirmatory method with a new protocol using the rapid DPP CVL screening test and EIE CVL confirmatory test. A study of diagnostic accuracy of these two protocols was done by comparing their performance using serum samples collected from a random sample of 780 dogs in an endemic area of VL. All samples were evaluated by culture and real time PCR; 766 out of the 780 dogs were tested using the previous protocol (IFI CVL + EIE CVL) and all 780 were tested using the current protocol (DPP CVL + EIE CVL). Performances of both diagnostic protocols were evaluated using a latent class variable as the gold standard. The current protocol had a higher specificity (0.98 vs. 0.95) and PPV (0.83 vs. 0.70) than the previous protocol, although sensitivity of these two protocols was similar (0.73). When tested using sera from asymptomatic animals, the current protocol had a much higher PPV (0.63 vs. 0.40) than the previous protocol (although the sensitivity of either protocol was the same, 0.71). Considering a range of theoretical CVL prevalences, the projected PPVs were higher for the current protocol than for the previous protocol for each theoretical prevalence value. The findings presented herein show that the current protocol performed better than previous protocol primarily by reducing false-positive results.

  2. The Rapid Test Based on Leishmania infantum Chimeric rK28 Protein Improves the Diagnosis of Canine Visceral Leishmaniasis by Reducing the Detection of False-Positive Dogs

    PubMed Central

    Borja, Lairton Souza; Tuy, Pétala Gardênia da Silva Estrela; Bastos, Leila Andrade; Solcà, Manuela da Silva; Amorim, Leila Denise Alves Ferreira; Veras, Patrícia Sampaio Tavares

    2016-01-01

    Visceral Leishmaniasis (VL) has spread to many urban centers worldwide. Dogs are considered the main reservoir of VL, because canine cases often precede the occurrence of human cases. Detection and euthanasia of serologically positive dogs is one of the primary VL control measures utilized in some countries, including Brazil. Using accurate diagnostic tests can minimize one undesirable consequence of this measure, culling false-positive dogs, and reduce the maintenance of false-negative dogs in endemic areas. In December 2011, the Brazilian Ministry of Health replaced the ELISA (EIE CVL) screening method and Indirect Immunofluorescence Test (IFI CVL) confirmatory method with a new protocol using the rapid DPP CVL screening test and EIE CVL confirmatory test. A study of diagnostic accuracy of these two protocols was done by comparing their performance using serum samples collected from a random sample of 780 dogs in an endemic area of VL. All samples were evaluated by culture and real time PCR; 766 out of the 780 dogs were tested using the previous protocol (IFI CVL + EIE CVL) and all 780 were tested using the current protocol (DPP CVL + EIE CVL). Performances of both diagnostic protocols were evaluated using a latent class variable as the gold standard. The current protocol had a higher specificity (0.98 vs. 0.95) and PPV (0.83 vs. 0.70) than the previous protocol, although sensitivity of these two protocols was similar (0.73). When tested using sera from asymptomatic animals, the current protocol had a much higher PPV (0.63 vs. 0.40) than the previous protocol (although the sensitivity of either protocol was the same, 0.71). Considering a range of theoretical CVL prevalences, the projected PPVs were higher for the current protocol than for the previous protocol for each theoretical prevalence value. The findings presented herein show that the current protocol performed better than previous protocol primarily by reducing false-positive results. PMID:26731098

  3. Coinfection of hepatitis A virus genotype IA and IIIA complicated with autoimmune hemolytic anemia, prolonged cholestasis, and false-positive immunoglobulin M anti-hepatitis E virus: a case report.

    PubMed

    Kim, Hee Sup; Jeong, Sook Hyang; Jang, Je Hyuck; Myung, Hyung Joon; Kim, Jin Wook; Bang, Soo Mee; Song, Sang Hoon; Kim, Haeryoung; Yun, Hae Sun

    2011-12-01

    A 37-year-old male presented with fever and jaundice was diagnosed as hepatitis A complicated with progressive cholestasis and severe autoimmune hemolytic anemia. He was treated with high-dose prednisolone (1.5 mg/kg), and eventually recovered. His initial serum contained genotype IA hepatitis A virus (HAV), which was subsequently replaced by genotype IIIA HAV. Moreover, at the time of development of hemolytic anemia, he became positive for immunoglobulin M (IgM) anti-hepatitis E virus (HEV). We detected HAV antigens in the liver biopsy specimen, while we detected neither HEV antigen in the liver nor HEV RNA in his serum. This is the first report of hepatitis A coinfected with two different genotypes manifesting with autoimmune hemolytic anemia, prolonged cholestasis, and false-positive IgM anti-HEV.

  4. Anticipated and Actual Reactions to Receiving HIV Positive Results Through Self-Testing Among Gay and Bisexual Men

    PubMed Central

    Carballo-Diéguez, Alex; Ibitoye, Mobolaji; Frasca, Timothy; Brown, William; Balan, Iván

    2014-01-01

    We explored anticipated and actual reactions to receiving HIV positive results through self-testing with a diverse group of 84 gay and bisexual men in New York City. Grounded Theory was used to investigate these reactions in a two-phase study, one hypothetical, followed by a practical phase in which self-tests were distributed and used. Three major themes emerged when participants were asked about their anticipated reactions to an HIV positive self-test result: managing emotional distress, obtaining HIV medical care, and postponing sexual activity. When participants were asked about their anticipated reactions to a partner’s HIV positive self-test result, five themes emerged: provide emotional support; refrain from engaging in sex with casual partner; avoid high-risk sexual activity with both main and casual partners; seek medical services; and obtain a confirmatory test result. Although none of the participants tested positive, seven of their partners did. Participants provided emotional support and linked their partners to support services. The availability of HIV self-testing kits offers potential opportunities to tackle HIV infection among individuals with high-risk practices. PMID:24858480

  5. Comparison of false-negative/positive results of intraoperative evoked potential monitoring between no and partial neuromuscular blockade in patients receiving propofol/remifentanil-based anesthesia during cerebral aneurysm clipping surgery: A retrospective analysis of 685 patients.

    PubMed

    Kim, Sung-Hoon; Jin, Seok-Joon; Karm, Myong-Hwan; Moon, Young-Jin; Jeong, Hye-Won; Kim, Jae-Won; Ha, Seung-Il; Kim, Joung-Uk

    2016-08-01

    Although the elicited responses of motor evoked potential (MEP) monitoring are very sensitive to suppression by anesthetic agents and muscle relaxants, the use of neuromuscular blockade (NMB) during MEP monitoring is still controversial because of serious safety concerns and diagnostic accuracy. Here, we evaluated the incidence of unacceptable movement and compared false-negative MEP results between no and partial NMB during cerebral aneurysm clipping surgery. We reviewed patient medical records for demographic data, anesthesia regimen, neurophysiology event logs, MEP results, and clinical outcomes. Patients were divided into 2 groups according to the intraoperative use of NMB: no NMB group (n = 276) and partial NMB group (n = 409). We compared the diagnostic accuracy of MEP results to predict postoperative outcomes between both groups. Additionally, we evaluated unwanted patient movement during MEP monitoring in both groups. Of the 685 patients, 622 (90.8%) manifested no intraoperative changes in MEP and no postoperative motor deficits. Twenty patients showed postoperative neurologic deficits despite preserved intraoperative MEP. False-positive MEP results were 3.6% in the no NMB group and 3.9% in the partial NMB group (P = 1.00). False-negative MEP results were 1.1% in the no NMB group and 4.2% in the partial NMB group (P = 0.02). No spontaneous movement or spontaneous respiration was observed in either group. Propofol/remifentanil-based anesthesia without NMB decreases the stimulation intensity of MEPs, which may reduce the false-negative ratio of MEP monitoring during cerebral aneurysm surgery. Our anesthetic protocol enabled reliable intraoperative MEP recording and patient immobilization during cerebral aneurysm clipping surgery. PMID:27559984

  6. Comparison of false-negative/positive results of intraoperative evoked potential monitoring between no and partial neuromuscular blockade in patients receiving propofol/remifentanil-based anesthesia during cerebral aneurysm clipping surgery: A retrospective analysis of 685 patients.

    PubMed

    Kim, Sung-Hoon; Jin, Seok-Joon; Karm, Myong-Hwan; Moon, Young-Jin; Jeong, Hye-Won; Kim, Jae-Won; Ha, Seung-Il; Kim, Joung-Uk

    2016-08-01

    Although the elicited responses of motor evoked potential (MEP) monitoring are very sensitive to suppression by anesthetic agents and muscle relaxants, the use of neuromuscular blockade (NMB) during MEP monitoring is still controversial because of serious safety concerns and diagnostic accuracy. Here, we evaluated the incidence of unacceptable movement and compared false-negative MEP results between no and partial NMB during cerebral aneurysm clipping surgery. We reviewed patient medical records for demographic data, anesthesia regimen, neurophysiology event logs, MEP results, and clinical outcomes. Patients were divided into 2 groups according to the intraoperative use of NMB: no NMB group (n = 276) and partial NMB group (n = 409). We compared the diagnostic accuracy of MEP results to predict postoperative outcomes between both groups. Additionally, we evaluated unwanted patient movement during MEP monitoring in both groups. Of the 685 patients, 622 (90.8%) manifested no intraoperative changes in MEP and no postoperative motor deficits. Twenty patients showed postoperative neurologic deficits despite preserved intraoperative MEP. False-positive MEP results were 3.6% in the no NMB group and 3.9% in the partial NMB group (P = 1.00). False-negative MEP results were 1.1% in the no NMB group and 4.2% in the partial NMB group (P = 0.02). No spontaneous movement or spontaneous respiration was observed in either group. Propofol/remifentanil-based anesthesia without NMB decreases the stimulation intensity of MEPs, which may reduce the false-negative ratio of MEP monitoring during cerebral aneurysm surgery. Our anesthetic protocol enabled reliable intraoperative MEP recording and patient immobilization during cerebral aneurysm clipping surgery.

  7. Effect of different hand positions on trunk and shoulder kinematics and reaction forces in sitting pivot transfer.

    PubMed

    Kim, Sung Shin; Her, Jin Gan; Ko, Tae Sung

    2015-07-01

    [Purpose] The purpose of this study was to compare the changes in trunk and shoulder angles, and reaction forces under the two hands elicited by different hand base of support positions during sitting pivot transfer. [Subjects and Methods] Eighteen unimpaired subjects performed independent sitting pivot transfer. Subjects performed sitting pivot transfer between an initial seat to a target seat by only using their hands positioned at the same height as and lower than the seat position. Trunk and shoulder kinematics, and reaction forces on the trailing and leading hands were calculated. Mean peak joint angles and forces were compared between the hand positions using the pared t-test for the lift phase of the transfer. [Results] There were significant increases in the trunk angles of forward and lateral flexion, even though rotation decreased while transferring in the lower hand position. Increased shoulder flexion, anterior/posterior forces and reduced lateral forces were also shown. [Conclusion] Placing the hands of the supporting arms lower than the seat position during sitting pivot transfer was identified as having biomechanical advantages. Therefore, the lower hand position can be recommended as an effective and safe method for sitting pivot transfer by patients with spinal cord injury and can be utilized as a reference data for considering the appropriate height of aids for a wheelchair. PMID:26310994

  8. Effect of different hand positions on trunk and shoulder kinematics and reaction forces in sitting pivot transfer.

    PubMed

    Kim, Sung Shin; Her, Jin Gan; Ko, Tae Sung

    2015-07-01

    [Purpose] The purpose of this study was to compare the changes in trunk and shoulder angles, and reaction forces under the two hands elicited by different hand base of support positions during sitting pivot transfer. [Subjects and Methods] Eighteen unimpaired subjects performed independent sitting pivot transfer. Subjects performed sitting pivot transfer between an initial seat to a target seat by only using their hands positioned at the same height as and lower than the seat position. Trunk and shoulder kinematics, and reaction forces on the trailing and leading hands were calculated. Mean peak joint angles and forces were compared between the hand positions using the pared t-test for the lift phase of the transfer. [Results] There were significant increases in the trunk angles of forward and lateral flexion, even though rotation decreased while transferring in the lower hand position. Increased shoulder flexion, anterior/posterior forces and reduced lateral forces were also shown. [Conclusion] Placing the hands of the supporting arms lower than the seat position during sitting pivot transfer was identified as having biomechanical advantages. Therefore, the lower hand position can be recommended as an effective and safe method for sitting pivot transfer by patients with spinal cord injury and can be utilized as a reference data for considering the appropriate height of aids for a wheelchair.

  9. Effect of different hand positions on trunk and shoulder kinematics and reaction forces in sitting pivot transfer

    PubMed Central

    Kim, Sung Shin; Her, Jin Gan; Ko, Tae Sung

    2015-01-01

    [Purpose] The purpose of this study was to compare the changes in trunk and shoulder angles, and reaction forces under the two hands elicited by different hand base of support positions during sitting pivot transfer. [Subjects and Methods] Eighteen unimpaired subjects performed independent sitting pivot transfer. Subjects performed sitting pivot transfer between an initial seat to a target seat by only using their hands positioned at the same height as and lower than the seat position. Trunk and shoulder kinematics, and reaction forces on the trailing and leading hands were calculated. Mean peak joint angles and forces were compared between the hand positions using the pared t-test for the lift phase of the transfer. [Results] There were significant increases in the trunk angles of forward and lateral flexion, even though rotation decreased while transferring in the lower hand position. Increased shoulder flexion, anterior/posterior forces and reduced lateral forces were also shown. [Conclusion] Placing the hands of the supporting arms lower than the seat position during sitting pivot transfer was identified as having biomechanical advantages. Therefore, the lower hand position can be recommended as an effective and safe method for sitting pivot transfer by patients with spinal cord injury and can be utilized as a reference data for considering the appropriate height of aids for a wheelchair. PMID:26310994

  10. The False Aneurysm

    PubMed Central

    Baird, R. J.; Doran, M. L.

    1964-01-01

    The clinical course of 18 patients with 25 false aneurysms is reviewed. In recent years false aneurysm has been most commonly seen as a complication of arterioplastic procedures in which prosthetic arterial grafts were used. The use of indwelling needles or cannulae, particularly in patients with a wide arterial pulse pressure, can also lead to the formation of false aneurysms. In the groin, a false aneurysm is frequently mistaken for an abscess. Early diagnosis and operative repair are essential to reduce the incidence of further complications. PMID:14180533

  11. A clinical and patch test study of patients with positive patch test reactions to fragrance mix in China.

    PubMed

    Lu, Xueyan; Li, Lin-feng; Wang, Wenhui; Wang, Jing

    2005-04-01

    The clinical and patch test (PT) features of patients with positive PT reactions to fragrance mix (FM) were studied. 378 consecutive eczema outpatients patch tested with a modified European standard series were analysed. 60 patients (15.9%) reacted to FM. No significant differences could be found between the ages of FM PT-positive and PT-negative patients [median age 40.5 (range from 18 years to 69 years) versus median age 37.5 (range from 5 years to 81 years), rank sum test, P = 0.301]. FM PT-positive rate in confirmed non-cosmetic allergic contact dermatitis patients was 30.4%, which was similar to that in confirmed cosmetic allergic contact dermatitis patients (30.4% versus 30%, chi(2) test, chi(2) = 0.0010, P = 0.972). The FM PT-positive rates were 10.8% in males and 18.2% in females (chi(2) test, chi(2) = 3.3443, P = 0.067). 76.7% of the patients with fragrance contact dermatitis were allergic to Chinese traditional medicine, which is much higher than that for cosmetic allergy (76.7% versus 43.3%, chi(2) test, chi(2) = 6.9446, P = 0.008). The positive PT rate to colophonium in the patients with positive PT reactions to FM is higher than that in the FM PT-negative patients (18.9% versus 3.0%, chi(2) test, chi(2) = 15.5471, P < 0.01). 62.5% of the patients reacted to colophonium were positive to FM. These results show that age has little effect on fragrance contact allergy. Other fragrant products besides cosmetics are also important sources of fragrance contact allergy. Chinese traditional medicine was an important factor in fragrance allergy in China. Patients with positive PT reactions to FM are more likely to react to colophonium.

  12. False Positive FDG PET/CT Resulting from Fibrous Dysplasia of the Bone in the Work-Up of a Patient with Bladder Cancer: Case Report and Review of the Literature.

    PubMed

    Aras, Mustafa; Ones, Tunc; Dane, Faysal; Nosheri, Omid; Inanir, Sabahat; Erdil, Tanju Yusuf; Turoglu, Halil Turgut

    2012-12-01

    Fibrous dysplasia of the bone (FDB) is a common, genetic, developmental disorder with a benign course. FDB can be seen anywhere throughout the skeleton. It is usually asymptomatic and found incidentally on imaging studies that are performed for other purposes. Although whole body 18 F-flourodeoxyglucose PET/CT (FDG PET/CT) is widely used in tumor imaging, infections and benign pathologies like FDB may cause false positive results. Herein we report the case of a 48-year-old FDB patient with transitional cell carcinoma of the urinary bladder. Restaging FDG PET/CT showed multiple mild to moderate hypermetabolic bone lesions which were initially misinterpreted as bone metastases. In this case report, we aimed to guide physicians in evaluating bone lesions in cancer patients with FDB in the light of the literature.

  13. Analysis of Reaction Times and Aerobic Capacities of Soccer Players According to Their Playing Positions

    ERIC Educational Resources Information Center

    Taskin, Cengiz; Karakoc, Onder; Taskin, Mine; Dural, Murat

    2016-01-01

    70 soccer players in Gaziantep amateur league voluntarily participated in this study, (average of their ages 19,17±1,34years, average of their heights 181,28±5,06 cm, average of their body weights 76,75±4,43 kg and average of their sports experiences 3,78±0,95 years) to analyze visual and auditory reaction times and aerobic capacities of amateur…

  14. Positive patch test reactions to nickel sulphate are not modified by neighbouring negative fragrance patch tests. A multicenter-study by the German contact dermatitis research group.

    PubMed

    Brasch, Jochen; Weichenthal, Michael; Szliska, Christiane; Löffler, Harald; Koch, Patrick; Grabbe, Jörgen; Mahler, Vera; Kreilgård, Bo; Hoeck, Ulla

    2006-01-01

    It is tacitly assumed that a positive patch test reaction is not affected by adjacent negative tests. However, despite its fundamental importance for the interpretation of test reactions this assumption has not been proven. To test this assumption, special TRUE-test strips were prepared containing placebo, nickel sulphate and fragrance mix as the only allergens, separated by distances of 1 cm and 7 cm and blinded to the investigators. Patients were synchronously tested with two strips. Out of 493 patients tested in 6 centres, the 93 with positive reactions to nickel sulphate only were evaluated. No relevant difference was found between positive nickel reactions in the two different distances to a negative fragrance patch test. We conclude that a positive patch test reaction is not affected by adjacent negative patch tests, which therefore can be neglected for the interpretation of positive reactions.

  15. Confinement and diffusion modulate bistability and stochastic switching in a reaction network with positive feedback

    NASA Astrophysics Data System (ADS)

    Mlynarczyk, Paul J.; Pullen, Robert H.; Abel, Steven M.

    2016-01-01

    Positive feedback is a common feature in signal transduction networks and can lead to phenomena such as bistability and signal propagation by domain growth. Physical features of the cellular environment, such as spatial confinement and the mobility of proteins, play important but inadequately understood roles in shaping the behavior of signaling networks. Here, we use stochastic, spatially resolved kinetic Monte Carlo simulations to explore a positive feedback network as a function of system size, system shape, and mobility of molecules. We show that these physical properties can markedly alter characteristics of bistability and stochastic switching when compared with well-mixed simulations. Notably, systems of equal volume but different shapes can exhibit qualitatively different behaviors under otherwise identical conditions. We show that stochastic switching to a state maintained by positive feedback occurs by cluster formation and growth. Additionally, the frequency at which switching occurs depends nontrivially on the diffusion coefficient, which can promote or suppress switching relative to the well-mixed limit. Taken together, the results provide a framework for understanding how confinement and protein mobility influence emergent features of the positive feedback network by modulating molecular concentrations, diffusion-influenced rate parameters, and spatiotemporal correlations between molecules.

  16. Confinement and diffusion modulate bistability and stochastic switching in a reaction network with positive feedback.

    PubMed

    Mlynarczyk, Paul J; Pullen, Robert H; Abel, Steven M

    2016-01-01

    Positive feedback is a common feature in signal transduction networks and can lead to phenomena such as bistability and signal propagation by domain growth. Physical features of the cellular environment, such as spatial confinement and the mobility of proteins, play important but inadequately understood roles in shaping the behavior of signaling networks. Here, we use stochastic, spatially resolved kinetic Monte Carlo simulations to explore a positive feedback network as a function of system size, system shape, and mobility of molecules. We show that these physical properties can markedly alter characteristics of bistability and stochastic switching when compared with well-mixed simulations. Notably, systems of equal volume but different shapes can exhibit qualitatively different behaviors under otherwise identical conditions. We show that stochastic switching to a state maintained by positive feedback occurs by cluster formation and growth. Additionally, the frequency at which switching occurs depends nontrivially on the diffusion coefficient, which can promote or suppress switching relative to the well-mixed limit. Taken together, the results provide a framework for understanding how confinement and protein mobility influence emergent features of the positive feedback network by modulating molecular concentrations, diffusion-influenced rate parameters, and spatiotemporal correlations between molecules.

  17. MSPI False Indication Probability Simulations

    SciTech Connect

    Dana Kelly; Kurt Vedros; Robert Youngblood

    2011-03-01

    This paper examines false indication probabilities in the context of the Mitigating System Performance Index (MSPI), in order to investigate the pros and cons of different approaches to resolving two coupled issues: (1) sensitivity to the prior distribution used in calculating the Bayesian-corrected unreliability contribution to the MSPI, and (2) whether (in a particular plant configuration) to model the fuel oil transfer pump (FOTP) as a separate component, or integrally to its emergency diesel generator (EDG). False indication probabilities were calculated for the following situations: (1) all component reliability parameters at their baseline values, so that the true indication is green, meaning that an indication of white or above would be false positive; (2) one or more components degraded to the extent that the true indication would be (mid) white, and “false” would be green (negative) or yellow (negative) or red (negative). In key respects, this was the approach taken in NUREG-1753. The prior distributions examined were the constrained noninformative (CNI) prior used currently by the MSPI, a mixture of conjugate priors, the Jeffreys noninformative prior, a nonconjugate log(istic)-normal prior, and the minimally informative prior investigated in (Kelly et al., 2010). The mid-white performance state was set at ?CDF = ?10 ? 10-6/yr. For each simulated time history, a check is made of whether the calculated ?CDF is above or below 10-6/yr. If the parameters were at their baseline values, and ?CDF > 10-6/yr, this is counted as a false positive. Conversely, if one or all of the parameters are set to values corresponding to ?CDF > 10-6/yr but that time history’s ?CDF < 10-6/yr, this is counted as a false negative indication. The false indication (positive or negative) probability is then estimated as the number of false positive or negative counts divided by the number of time histories (100,000). Results are presented for a set of base case parameter values

  18. Reducing false-positive biopsies: a pilot study to reduce benign biopsy rates for BI-RADS 4A/B assessments through testing risk stratification and new thresholds for intervention.

    PubMed

    Flowers, Chris I; O'Donoghue, Cristina; Moore, Dan; Goss, Adeline; Kim, Danny; Kim, June-Ho; Elias, Sjoerd G; Fridland, Julia; Esserman, Laura J

    2013-06-01

    The aim of this study is to evaluate Breast Imaging Reporting and Data Systems (BI-RADS) 4A/B subcategory risk estimates for ductal carcinoma in situ (DCIS) and invasive cancer (IC), determining whether changing the proposed cutoffs to a higher biopsy threshold could safely increase cancer-to-biopsy yields while minimizing false-positive biopsies. A prospective clinical trial was performed to evaluate BI-RADS 4 lesions from women seen in clinic between January 2006 and March 2007. An experienced radiologist prospectively estimated a percent risk-estimate for DCIS and IC. Truth was determined by histopathology or 4-year follow-up negative for malignancy. Risk estimates were used to generate receiver-operating characteristic (ROC) curves. Biopsy rates, cancer-to-biopsy yields, and type of malignancies missed were then calculated across postulated risk thresholds. A total of 124 breast lesions were evaluated from 213 women. An experienced radiologist gave highly accurate risk estimates for IC, DCIS alone, or the combination with an area under ROC curve of 0.91 (95 % CI 0.84-0.99) (p < 0.001), 0.81 (95 % CI 0.69-0.93) (p = 0.011), and 0.89 (95 % CI 0.83-0.95) (p < 0.001), respectively. The cancer-to-biopsy yield was 30 %. Three hypothetical thresholds for intervention were analyzed: (1) DCIS or IC ≥ 10 %; (2) DCIS ≥ 50 % or IC ≥ 10 %; and (3) IC ≥ 10 %, which translated to 22, 48, and 56 % of biopsies avoided; cancer-to-biopsy yields of 36, 47, and 46 %; and associated chance of missing an IC of 0, 1, and 2 %, respectively. Expert radiologists estimate risk of IC and DCIS with a high degree of accuracy. Increasing the cut off point for recommending biopsy, substituting with a short-term follow-up protocol with biopsy if any change, may safely reduce the number of false-positive biopsies.

  19. Ground reaction forces and kinematics of plant leg position during instep kicking in male and female collegiate soccer players.

    PubMed

    Orloff, Heidi; Sumida, Bryce; Chow, Janna; Habibi, Lalae; Fujino, Aaron; Kramer, Brian

    2008-05-01

    The players' ability to achieve the greatest distance in kicking is determined by their efficiency in transferring kinetic energy from the body to the ball. The purpose of this study was to compare the kinetics and kinematics of the plant leg position between male and female collegiate soccer players during instep kicking. Twenty-three soccer players (11 males and 12 females) were filmed in both the sagittal and posterior views while performing a maximal instep kick. Plant leg kinetic data were also collected using an AMTI 1000 force platform. There were no significant differences between the sexes in plant leg position, but females had significantly greater trunk lean, plant leg angle, and medial-lateral ground reaction force than the males. Males showed higher vertical ground reaction forces at ball contact, but there were no significant differences in ball speed at take-off between the sexes. Ball speed at take-off was inversely related to peak anterior-posterior ground reaction force (-0.65). The anatomical differences between the sexes were reflected in greater trunk lean and lower leg angle in the females.

  20. Positive feedback produces broad distributions in maximum activation attained within a narrow time window in stochastic biochemical reactions

    NASA Astrophysics Data System (ADS)

    Das, Jayajit

    2013-03-01

    Stochastic fluctuations in biochemical reactions can regulate single cell decision processes. Using exact solutions and semi-analytical methods we calculate distributions of the maximum value (N) of species concentrations (Pmax (N)) and the time (t) taken to reach the maximum value (Pmax (t)) in minimal models of stochastic chemical reactions commonly found in cell signaling systems. We find, the presence of positive feedback interactions make Pmax (N) more spread out with a higher ``peakedness'' in Pmax (t) . Thus positive feedback interactions may help single cells to respond sensitively to a stimulus when cell decision processes require upregulation of activated forms of key proteins to a threshold number within a time window. Moreover, unlike other models of strongly correlated random variables such as Brownian walks or fluctuating interfaces, the extreme value distributions for the chemical reactions display multiscaling behavior emphasizing the presence of many time scales in cell signaling kinetics. This work was funded by the Research Institute at the Nationwide Children's Hospital and a grant (1R56AI090115-01A1) from the NIH.

  1. False "highlighting" with Wood's lamp.

    PubMed

    Silverberg, Jonathan I; Silverberg, Nanette B

    2014-01-01

    Wood's lamp evaluation is used to diagnose pigmentary disorders. For example, vitiligo typically demonstrates lesional enhancement under Wood's lamp evaluation. Numerous false positive enhancing lesions can be noted in the skin. We describe a 5-year-old Hispanic boy who had painted his face with highlighter, producing enhancing lesions under Wood's lamp. Physicians who use Wood's lamp should be aware that the appearance of markers and highlighter can mimic that of true clinical illnesses.

  2. Stereoselective synthesis and reactions of secondary alkyllithium reagents functionalized at the 3-position.

    PubMed

    Moriya, Kohei; Didier, Dorian; Simon, Meike; Hammann, Jeffrey M; Berionni, Guillaume; Karaghiosoff, Konstantin; Zipse, Hendrik; Mayr, Herbert; Knochel, Paul

    2015-02-23

    Secondary alkyllithium reagents bearing an OTBS group (TBS=tert-butyldimethylsilyl) at the 3-position can be prepared stereoconvergently through an I/Li exchange from a diastereomeric mixture of the corresponding secondary alkyl iodides. These lithium reagents react with a range of electrophiles, including carbon electrophiles, with retention of configuration to yield various 1,3-difunctionalized derivatives with good diastereoselectivities. Kinetic studies show that the 3-siloxy group strongly accelerates the epimerization at the lithium-substituted carbon atom. This method offers a new way to construct chiral open-chain molecules with excellent stereoselectivity. PMID:25640227

  3. Posttraumatic growth moderates the effects of posttraumatic stress symptoms on adjustment and positive affective reactions in digestive system cancer patients.

    PubMed

    Ben-Zur, Hasida; Cohen, Miri; Gouzman, Julia

    2015-01-01

    The study aims were twofold: (1) To investigate the associations of posttraumatic stress symptoms (PTSS) and posttraumatic growth (PTG) with adjustment and affective reactions of digestive system cancer patients and (2) To assess the moderating effects of PTG on the associations of PTSS with adjustment and affective reactions. The sample consisted of 200 respondents 1-4 years following diagnosis and treatment for digestive system cancer. Participants completed questionnaires assessing PTSS, PTG, adjustment, positive affect (PA), and negative affect (NA). The results showed that PTG was positively associated with adjustment and PA, while PTSS was negatively associated with these outcomes and positively associated with NA. Moderation effects of PTG were also observed: The negative associations between PTSS and adjustment or PA were weaker under high levels than under low levels of PTG. It was concluded that PTG is important both as a contributor to better adjustment and PA, as well as a moderator of the detrimental effects of PTSS on adjustment and PA following recovery from cancer. Thus, when developing post-cancer intervention programs, PTG should be viewed as a factor to be encouraged and nurtured for the benefit of cancer patients' adjustment and their long-term well-being.

  4. Moon - False Color Mosaic

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This false-color photograph is a composite of 15 images of the Moon taken through three color filters by Galileo's solid-state imaging system during the spacecraft's passage through the Earth-Moon system on December 8, 1992. When this view was obtained, the spacecraft was 425,000 kilometers (262,000 miles) from the Moon and 69,000 kilometers (43,000 miles) from Earth. The false-color processing used to create this lunar image is helpful for interpreting the surface soil composition. Areas appearing red generally correspond to the lunar highlands, while blue to orange shades indicate the ancient volcanic lava flow of a mare, or lunar sea. Bluer mare areas contain more titanium than do the orange regions. Mare Tranquillitatis, seen as a deep blue patch on the right, is richer in titanium than Mare Serenitatis, a slightly smaller circular area immediately adjacent to the upper left of Mare Tranquillitatis. Blue and orange areas covering much of the left side of the Moon in this view represent many separate lava flows in Oceanus Procellarum. The small purple areas found near the center are pyroclastic deposits formed by explosive volcanic eruptions. The fresh crater Tycho, with a diameter of 85 kilometers (53 miles), is prominent at the bottom of the photograph, where part of the Moon's disk is missing.

  5. Persistent ICT malaria P.f/P.v panmalarial and HRP2 antigen reactivity after treatment of Plasmodium falciparum malaria is associated with gametocytemia and results in false-positive diagnoses of Plasmodium vivax in convalescence.

    PubMed

    Tjitra, E; Suprianto, S; McBroom, J; Currie, B J; Anstey, N M

    2001-03-01

    A problem with rapid Plasmodium falciparum-specific antigen histidine-rich protein 2 (HRP2) detection tests for malaria is the persistence of antigen in blood after the disappearance of asexual-stage parasitemia and clinical symptoms, resulting in false-positive (FP) test results following treatment. The ICT P.f/P.v immunochromatographic test detects both HRP2 and a panmalarial antigen (PMA) found in both P. falciparum and Plasmodium vivax. To examine posttreatment antigen persistence with this test and whether persistent sexual-stage forms (gametocytes) are a cause of FP tests after treatment, we compared serial antigen test results with microscopy results from patients symptomatic with P. falciparum malaria in Indonesia for 28 days following treatment with chloroquine (CQ; n = 66), sulfadoxine-pyrimethamine (SP; n = 36), and artesunate plus sulfadoxine-pyrimethamine (ART + SP; n = 15). Persistent FP antigenemia following SP treatment occurred in 29% (HRP2) and 42% (PMA) of the patients on day 7 and in 10% (HRP2) and 23% (PMA) on day 14. The high rates of persistent HRP2 and PMA antigenemia following CQ and SP treatment were strongly associated with the presence of gametocytemia, with the proportion with gametocytes on day 7 posttreatment being significantly greater in those with FP results than in those with true-negative PMA and HRP2 results. Gametocyte frequency on day 14 post-SP treatment was also greater in those with FP PMA results. Following SP treatment, PMA persisted longer than HRP2, giving an FP diagnosis of P. vivax in up to 16% of patients on day 14, with all FP P. vivax diagnoses having gametocytemia. In contrast, PMA was rapidly cleared following ART + SP treatment in association with rapid clearance of gametocytemia. Gametocytes appear to be an important cause of persistent posttreatment panmalarial antigenemia in areas of endemicity and may also contribute in part to persistent HRP2 antigenemia following treatment. PMID:11230422

  6. False color viewing device

    DOEpatents

    Kronberg, J.W.

    1991-05-08

    This invention consists of a viewing device for observing objects in near-infrared false-color comprising a pair of goggles with one or more filters in the apertures, and pads that engage the face for blocking stray light from the sides so that all light reaching, the user`s eyes come through the filters. The filters attenuate most visible light and pass near-infrared (having wavelengths longer than approximately 700 nm) and a small amount of blue-green and blue-violet (having wavelengths in the 500 to 520 nm and shorter than 435 nm, respectively). The goggles are useful for looking at vegetation to identify different species and for determining the health of the vegetation, and to detect some forms of camouflage.

  7. False color viewing device

    DOEpatents

    Kronberg, J.W.

    1992-10-20

    A viewing device for observing objects in near-infrared false-color comprising a pair of goggles with one or more filters in the apertures, and pads that engage the face for blocking stray light from the sides so that all light reaching the user's eyes come through the filters. The filters attenuate most visible light and pass near-infrared (having wavelengths longer than approximately 700 nm) and a small amount of blue-green and blue-violet (having wavelengths in the 500 to 520 nm and shorter than 435 nm, respectively). The goggles are useful for looking at vegetation to identify different species and for determining the health of the vegetation, and to detect some forms of camouflage. 7 figs.

  8. False color viewing device

    DOEpatents

    Kronberg, James W.

    1992-01-01

    A viewing device for observing objects in near-infrared false-color comprising a pair of goggles with one or more filters in the apertures, and pads that engage the face for blocking stray light from the sides so that all light reaching the user's eyes come through the filters. The filters attenuate most visible light and pass near-infrared (having wavelengths longer than approximately 700 nm) and a small amount of blue-green and blue-violet (having wavelengths in the 500 to 520 nm and shorter than 435 nm, respectively). The goggles are useful for looking at vegetation to identify different species and for determining the health of the vegetation, and to detect some forms of camouflage.

  9. Hybrid capacitors utilizing halogen-based redox reactions at interface between carbon positive electrode and aqueous electrolytes

    NASA Astrophysics Data System (ADS)

    Yamazaki, Shigeaki; Ito, Tatsuya; Murakumo, Yuka; Naitou, Masashi; Shimooka, Toshiharu; Yamagata, Masaki; Ishikawa, Masashi

    2016-09-01

    We propose novel hybrid capacitors (HCs) with electrolyte-involved redox reactions of bromide or iodide species by pretreatment of an activated carbon positive electrode. The treatment is simple; impregnation of pores at an activated carbon fiber cloth (ACFC) as a positive electrode with bromine- or iodine-containing water before cell assembly. The treated positive electrode is applied to a HC cell with a non-treated negative electrode of ACFC and its electrochemical performance is investigated by galvanostatic cycling and leakage current tests. Few studies on such "electrolytic" charge storage systems have provided acceptable capacitor performance because of inevitable self-discharge caused by diffusion of charged species form an electrode to the other one through an electrolyte. Nevertheless, our electrolyte-redox-based HCs show excellent performance without undesirable diffusion of charged species. Moreover, the present HC utilizing a bromide redox system fulfills a practical cell voltage of 1.8 V in spite of an aqueous electrolyte system. This high voltage provides excellent energy density, which is 5 times higher than that in a conventional aqueous electric double-layer capacitor (EDLC), and 1.2 times higher even than that in a 2.7 V-class non-aqueous EDLC, while keeping high charge-discharge rate capability.

  10. Radiologists' interpretive efficiency and variability in true- and false-positive detection when screen-reading with tomosynthesis (3D-mammography) relative to standard mammography in population screening.

    PubMed

    Svahn, Tony M; Macaskill, Petra; Houssami, Nehmat

    2015-12-01

    We examined interpretive efficiency and variability in true- and false-positive detection (TP, FP) for radiologists screen-reading with digital breast tomosynthesis as adjunct to full-field digital mammography (2D/3D) relative to 2D alone in population-based screening studies. A systematic literature search was performed to identify screening studies that provided radiologist-specific data for TP and FP detection. Radiologist interpretive efficiency (trade-off between TPs and FPs) was calculated using the FP:TP ratio which expresses the number of FP recalls for each screen-detected breast cancer. We modeled a pooled FP:TP ratio to assess variability in radiologists' interpretive efficiency at study-level using random effects logistic regression. FP:TP ratio improved (ratio decreased) for 2D/3D screen-reading (relative to 2D) for a majority of radiologists (18 of 22) across all studies. Variability in radiologists' FP:TP ratio was consistently lower in all studies for 2D/3D screen-reading, as suggested by lower variance in ratios. Study-level pooled FP:TP ratio for 2D- and 2D/3D-mammography respectively, were 5.96 (95%CI: 4.08 to 8.72) and 3.17 (95%CI: 2.25 to 4.47) for the STORM trial; 10.25 (95%CI: 6.42 to 16.35) and 7.07 (95%CI: 4.99 to 10.02) for the Oslo trial; and 20.84 (95%CI: 13.95 to 31.12) and 8.37 (95%CI: 5.87 to 11.93) for the Houston study. This transfers into study-level improved interpretative efficiencies of 48%, 30% and 55%, respectively, for 2D/3D screen-reading (relative to 2D). In summary, study-level FP:TP trade-off improved using 2D/3D-mammography for all studies, which was also seen for most individual radiologists. There was variability in the FP:TP trade-off between readers and studies for 2D-as well as for 2D/3D-interpretations but variability in radiologists' interpretive efficiency was relatively lower using 2D/3D-mammography.

  11. A Very Low Geno2pheno False Positive Rate Is Associated with Poor Viro-Immunological Response in Drug-Naïve Patients Starting a First-Line HAART

    PubMed Central

    Armenia, Daniele; Soulie, Cathia; Di Carlo, Domenico; Fabeni, Lavinia; Gori, Caterina; Forbici, Federica; Svicher, Valentina; Bertoli, Ada; Sarmati, Loredana; Giuliani, Massimo; Latini, Alessandra; Boumis, Evangelo; Zaccarelli, Mauro; Bellagamba, Rita; Andreoni, Massimo; Marcelin, Anne-Geneviève; Calvez, Vincent; Antinori, Andrea; Ceccherini-Silberstein, Francesca; Perno, Carlo-Federico; Santoro, Maria Mercedes

    2014-01-01

    Background We previously found that a very low geno2pheno false positive rate (FPR ≤2%) defines a viral population associated with low CD4 cell count and the highest amount of X4-quasispecies. In this study, we aimed at evaluating whether FPR ≤2% might impact on the viro-immunological response in HIV-1 infected patients starting a first-line HAART. Methods The analysis was performed on 305 HIV-1 B subtype infected drug-naïve patients who started their first-line HAART. Baseline FPR (%) values were stratified according to the following ranges: ≤2; 2–5; 5–10; 10–20; 20–60; >60. The impact of genotypically-inferred tropism on the time to achieve immunological reconstitution (a CD4 cell count gain from HAART initiation ≥150 cells/mm3) and on the time to achieve virological success (the first HIV-RNA measurement <50 copies/mL from HAART initiation) was evaluated by survival analyses. Results Overall, at therapy start, 27% of patients had FPR ≤10 (6%, FPR ≤2; 7%, FPR 2–5; 14%, FPR 5–10). By 12 months of therapy the rate of immunological reconstitution was overall 75.5%, and it was significantly lower for FPR ≤2 (54.1%) in comparison to other FPR ranks (78.8%, FPR 2–5; 77.5%, FPR 5–10; 71.7%, FPR 10–20; 81.8%, FPR 20–60; 75.1%, FPR >60; p = 0.008). The overall proportion of patients achieving virological success was 95.5% by 12 months of therapy. Multivariable Cox analyses showed that patients having pre-HAART FPR ≤2% had a significant lower relative adjusted hazard [95% C.I.] both to achieve immunological reconstitution (0.37 [0.20–0.71], p = 0.003) and to achieve virological success (0.50 [0.26–0.94], p = 0.031) than those with pre-HAART FPR >60%. Conclusions Beyond the genotypically-inferred tropism determination, FPR ≤2% predicts both a poor immunological reconstitution and a lower virological response in drug-naïve patients who started their first-line therapy. This parameter could be useful to identify patients

  12. Radiologists' interpretive efficiency and variability in true- and false-positive detection when screen-reading with tomosynthesis (3D-mammography) relative to standard mammography in population screening.

    PubMed

    Svahn, Tony M; Macaskill, Petra; Houssami, Nehmat

    2015-12-01

    We examined interpretive efficiency and variability in true- and false-positive detection (TP, FP) for radiologists screen-reading with digital breast tomosynthesis as adjunct to full-field digital mammography (2D/3D) relative to 2D alone in population-based screening studies. A systematic literature search was performed to identify screening studies that provided radiologist-specific data for TP and FP detection. Radiologist interpretive efficiency (trade-off between TPs and FPs) was calculated using the FP:TP ratio which expresses the number of FP recalls for each screen-detected breast cancer. We modeled a pooled FP:TP ratio to assess variability in radiologists' interpretive efficiency at study-level using random effects logistic regression. FP:TP ratio improved (ratio decreased) for 2D/3D screen-reading (relative to 2D) for a majority of radiologists (18 of 22) across all studies. Variability in radiologists' FP:TP ratio was consistently lower in all studies for 2D/3D screen-reading, as suggested by lower variance in ratios. Study-level pooled FP:TP ratio for 2D- and 2D/3D-mammography respectively, were 5.96 (95%CI: 4.08 to 8.72) and 3.17 (95%CI: 2.25 to 4.47) for the STORM trial; 10.25 (95%CI: 6.42 to 16.35) and 7.07 (95%CI: 4.99 to 10.02) for the Oslo trial; and 20.84 (95%CI: 13.95 to 31.12) and 8.37 (95%CI: 5.87 to 11.93) for the Houston study. This transfers into study-level improved interpretative efficiencies of 48%, 30% and 55%, respectively, for 2D/3D screen-reading (relative to 2D). In summary, study-level FP:TP trade-off improved using 2D/3D-mammography for all studies, which was also seen for most individual radiologists. There was variability in the FP:TP trade-off between readers and studies for 2D-as well as for 2D/3D-interpretations but variability in radiologists' interpretive efficiency was relatively lower using 2D/3D-mammography. PMID:26433751

  13. Prophylactic use of danaparoid in high-risk pregnancy with heparin-induced thrombocytopaenia-positive skin reaction.

    PubMed

    Myers, Bethan; Westby, John; Strong, Jane

    2003-07-01

    We describe a case where danaparoid was used prophylactically in a high-risk twin pregnancy following the development of heparin-allergy while on prophylactic dalteparin. Danaparoid was substituted for dalteparin at 20 weeks of pregnancy following the development of a severe skin reaction while on the low molecular weight heparin. Although there was no significant fall in platelet count, an aggregation assay for heparin-induced thrombocytopaenia was positive. The skin lesions rapidly resolved following the change to subcutaneous danaparoid. Delivery was by emergency caesarian section at 35 weeks under a general anaesthetic, as a dose of danaparoid had been given 6 h prior to delivery. A sample of breast milk showed no anti-activated factor X activity. Danaparoid was continued post-delivery until the patient was fully warfarinized. To our knowledge, there are no previous reports of the use of danaparoid in this setting. PMID:12851535

  14. Canine atopic dermatitis in Greece: clinical observations and the prevalence of positive intradermal test reactions in 91 spontaneous cases.

    PubMed

    Saridomichelakis, M N; Koutinas, A F; Gioulekas, D; Leontidis, L

    1999-07-01

    Atopic dermatitis was diagnosed in a total of 91 dogs by combining the compatible historical evidence and clinical signs with the presence of one or more positive intradermal test reactions well correlated with the exposure to the aeroallergens and the seasonality of the clinical signs. Compared to the general hospital population Yorkshire terriers, Chinese Shar-Peis and cocker spaniels showed a strong predilection. No such predilection was found regarding the sex of the animals. The age of the dogs at the onset of the clinical signs ranged from 2 months to 8 years (median: 2.5 years). Moderate to severe pruritus, noticed in all the 91 dogs, was either localized (29/91) or generalized (64/91) and non-seasonal (43/91), seasonal (19/91) or of unknown seasonality (29/91). The most common cutaneous lesions included erythema, hyperpigmentation, hypotrichosis and crusts; their body distribution was generalized (64%) or localized (36%) with the feet as the most common site of involvement. Five dogs that had unlesional skin were significantly younger and had been pruritic for a shorter period of time compared to the majority of our study population. Otitis externa (43/91) and bacterial pyoderma (30/91) were the most common conditions associated with atopic dermatitis, while the prevalence of Malassezia dermatitis was very low (2/91). Of the other allergic skin diseases flea allergic dermatitis was the most common (29/91) followed by food hypersensitivity (2 out of the 15 dogs tested). The majority of the dogs demonstrated multiple sensitivities to the 50 aeroallergens tested, while domestic mites (77/91), and particularly Dermatophagoides farinae (64/91), were the most commonly implicated. The total number of the positive intradermal test reactions was increasing parallel to the age of the dogs but it was negatively associated with the presence of skin lesions on the carpal and tarsal joints. PMID:10490235

  15. Nestin- and doublecortin-positive cells reside in adult spinal cord meninges and participate in injury-induced parenchymal reaction.

    PubMed

    Decimo, Ilaria; Bifari, Francesco; Rodriguez, Francisco Javier; Malpeli, Giorgio; Dolci, Sissi; Lavarini, Valentina; Pretto, Silvia; Vasquez, Sandra; Sciancalepore, Marina; Montalbano, Alberto; Berton, Valeria; Krampera, Mauro; Fumagalli, Guido

    2011-12-01

    Adult spinal cord has little regenerative potential, thus limiting patient recovery following injury. In this study, we describe a new population of cells resident in the adult rat spinal cord meninges that express the neural stem/precursor markers nestin and doublecortin. Furthermore, from dissociated meningeal tissue a neural stem cell population was cultured in vitro and subsequently shown to differentiate into functional neurons or mature oligodendrocytes. Proliferation rate and number of nestin- and doublecortin-positive cells increased in vivo in meninges following spinal cord injury. By using a lentivirus-labeling approach, we show that meningeal cells, including nestin- and doublecortin-positive cells, migrate in the spinal cord parenchyma and contribute to the glial scar formation. Our data emphasize the multiple roles of meninges in the reaction of the parenchyma to trauma and indicate for the first time that spinal cord meninges are potential niches harboring stem/precursor cells that can be activated by injury. Meninges may be considered as a new source of adult stem/precursor cells to be further tested for use in regenerative medicine applied to neurological disorders, including repair from spinal cord injury.

  16. A novel duplex real time quantitative reverse transcription polymerase chain reaction for rubella virus with armored RNA as a noncompetitive internal positive control.

    PubMed

    Zhao, Lihong; Li, Ruiying; Liu, Aihua; Zhao, Shuping

    2015-07-01

    The objective of this study was to build and apply a duplex real time quantitative reverse transcription-polymerase chain reaction (RT-PCR) for rubella virus. Firstly, a 60-bp-long armored RV RNA was constructed in the laboratory. Secondly, a duplex real time RT-PCR assay was established. Thirdly, the 60-bp-long armored RV RNA was used as an internal positive control (IPC) for the duplex real time RT-PCR. And finally the duplex real time RT-PCR assay was applied to detect RV RNA in clinical specimens. The in-house assay has a high amplification efficiency (0.99), a high analytical sensitivity (200 copies/mL), and a good reproducibility. The diagnostic specificity and sensitivity of the in-house assay were both 100%, due to the monitoring of the armored RV RNA IPC. Therefore, the in-house duplex real time quantitative RT-PCR assay is a specific, sensitive, reproducible and accurate assay for quantitation of RV RNA in clinical specimens. And noncompetitive armored RV RNA IPC can monitor RT-PCR inhibition and prevent false-negative and inaccurate results in the real time detection system.

  17. Sensitivity analysis of the position of the intervertebral centres of reaction in upright standing--a musculoskeletal model investigation of the lumbar spine.

    PubMed

    Zander, Thomas; Dreischarf, Marcel; Schmidt, Hendrik

    2016-03-01

    The loads between adjacent vertebrae can be generalised as a single spatial force acting at the intervertebral centre of reaction. The exact position in vivo is unknown. However, in rigid body musculoskeletal models that simulate upright standing, the position is generally assumed to be located at the discs' centres of rotation. The influence of the antero-posterior position of the centre of reaction on muscle activity and joint loads remains unknown. Thus, by using an inverse dynamic model, we varied the position of the centre of reaction at L4/L5 (i), simultaneously at all lumbar levels (ii), and by optimisation at all lumbar levels (iii). Variation of the centres of reaction can considerably influence the activities of lumbar muscles and the joint forces between vertebrae. The optimisation of the position of the centre of reaction reduced the maximum lumbar muscle activity and axial joint forces at L4/L5 from 17.5% to 1.5% of the muscle strength and from 490 N to 390 N, respectively. Thus, when studying individual postures, such as for therapeutic or preventive evaluations, potential differences between the centre of reaction and the centre of rotation might influence the study results. These differences could be taken into account by sensitivity analyses.

  18. Measurement of the target-normal single-spin asymmetry in quasielastic scattering from the reaction He3(e,e')

    SciTech Connect

    Zhang, Y. -W.; Long, E.; Mihovilovič, M.; Jin, G.; Allada, K.; Anderson, B.; Annand, J. R. M.; Averett, T.; Ayerbe-Gayoso, C.; Boeglin, W.; Bradshaw, P.; Camsonne, A.; Canan, M.; Cates, G. D.; Chen, C.; Chen, J. P.; Chudakov, E.; De Leo, R.; Deng, X.; Deur, A.; Dutta, C.; El Fassi, L.; Flay, D.; Frullani, S.; Garibaldi, F.; Gao, H.; Gilad, S.; Gilman, R.; Glamazdin, O.; Golge, S.; Gomez, J.; Hansen, O.; Higinbotham, D. W.; Holmstrom, T.; Huang, J.; Ibrahim, H.; de Jager, C. W.; Jensen, E.; Jiang, X.; John, J. St.; Jones, M.; Kang, H.; Katich, J.; Khanal, H. P.; King, P.; Korsch, W.; LeRose, J.; Lindgren, R.; Lu, H. -J.; Luo, W.; Markowitz, P.; Meziane, M.; Michaels, R.; Moffit, B.; Monaghan, P.; Muangma, N.; Nanda, S.; Norum, B. E.; Pan, K.; Parno, D.; Piasetzky, E.; Posik, M.; Punjabi, V.; Puckett, A. J. R.; Qian, X.; Qiang, Y.; Qiu, X.; Riordan, S.; Ron, G.; Saha, A.; Sawatzky, B.; Schiavilla, R.; Schoenrock, B.; Shabestari, M.; Shahinyan, A.; Širca, S.; Subedi, R.; Sulkosky, V.; Tobias, W. A.; Tireman, W.; Urciuoli, G. M.; Wang, D.; Wang, K.; Wang, Y.; Watson, J.; Wojtsekhowski, B.; Ye, Z.; Zhan, X.; Zhang, Y.; Zheng, X.; Zhao, B.; Zhu, L.

    2015-10-22

    We report the first measurement of the target single-spin asymmetry, Ay, in quasi-elastic scattering from the inclusive reaction 3He↑ (e,e') on a 3He gas target polarized normal to the lepton scattering plane. Assuming time-reversal invariance, this asymmetry is strictly zero for one-photon exchange. A non-zero Ay can arise from the interference between the one- and two-photon exchange processes which is sensitive to the details of the sub-structure of the nucleon. An experiment recently completed at Jefferson Lab yielded asymmetries with high statistical precision at Q2= 0.13, 0.46 and 0.97 GeV2. These measurements demonstrate, for the first time, that the 3He asymmetry is clearly non-zero and negative with a statistical significance of (8-10)σ. Using measured proton-to-3He cross-section ratios and the effective polarization approximation, neutron asymmetries of -(1-3)% were obtained. The neutron asymmetry at high Q2 is related to moments of the Generalized Parton Distributions (GPDs). Our measured neutron asymmetry at Q2=0.97 GeV2 agrees well with a prediction based on two-photon exchange using a GPD model and in addition provides a new independent constraint on these distributions.

  19. The false-negative Meckel's scan

    SciTech Connect

    Wilton, G.; Froelich, J.W.

    1982-10-01

    A case is presented of a 17-month-old girl who underwent two Meckel's scans with /sup 99m/Tc pertechnetate. The initial study was interpreted as normal while a subsequent study five days later was definitely positive. Surgery immediately following the positive Meckel's scan demonstrated a Meckel's diverticulum containing gastric mucosa without evidence of active hemorrhage. This prompted a review of the literature in reference to false-negative Meckel's scans which revealed a wide variance in the reported incidence of false-negative examinations. Repeat scintigraphy in the face of a strong clinical suspicion after an initial normal study may decrease the indicence of false-negative imaging series.

  20. Ab Initio many-body calculations of the H3(d,n)He4 and He3(d,p)He4 fusion reactions

    SciTech Connect

    Navráail, Petr; Quaglioni, Sofia

    2012-01-24

    We apply the ab initio no-core shell model combined with the resonating-group method approach to calculate the cross sections of the 3H(d,n)4He and 3He(d,p)4He fusion reactions. These are important reactions for the big bang nucleosynthesis and the future of energy generation on Earth. Starting from a selected similarity-transformed chiral nucleon-nucleon interaction that accurately describes two-nucleon data, we performed many-body calculations that predict the S factor of both reactions. Virtual three-body breakup effects are obtained by including excited pseudostates of the deuteron in the calculation. Lastly, our results are in satisfactory agreement with experimental data and pave the way for microscopic investigations of polarization and electron-screening effects, of the 3H(d,γn)4He bremsstrahlung and other reactions relevant to fusion research.

  1. Sensitive detection of miRNA by using hybridization chain reaction coupled with positively charged gold nanoparticles.

    PubMed

    Miao, Xiangmin; Ning, Xue; Li, Zongbing; Cheng, Zhiyuan

    2016-01-01

    Positively charged gold nanoparticles (+)AuNPs can adsorb onto the negatively charged surface of single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA). Herein, long-range dsDNA polymers could form based on the hybridization chain reaction (HCR) of two hairpin probes (H1 and H2) by using miRNA-21 as an initiator. (+)AuNPs could adsorb onto the negatively charged surface of such long-range dsDNA polymers based on the electrostatic adsorption, which directly resulted in the precipitation of (+)AuNPs and the decrease of (+)AuNPs absorption spectra. Under optimal conditions, miRNA-21 detection could be realized in the range of 20 pM-10 nM with a detection limit of 6.8 pM. In addition, (+)AuNPs used here are much more stable than commonly used negatively charged gold nanoparticles ((-)AuNPs) in mixed solution that contained salt, protein or other metal ions. Importantly, the assay could realize the detection of miRNA in human serum samples. PMID:27576601

  2. Sensitive detection of miRNA by using hybridization chain reaction coupled with positively charged gold nanoparticles

    PubMed Central

    Miao, Xiangmin; Ning, Xue; Li, Zongbing; Cheng, Zhiyuan

    2016-01-01

    Positively charged gold nanoparticles (+)AuNPs can adsorb onto the negatively charged surface of single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA). Herein, long-range dsDNA polymers could form based on the hybridization chain reaction (HCR) of two hairpin probes (H1 and H2) by using miRNA-21 as an initiator. (+)AuNPs could adsorb onto the negatively charged surface of such long-range dsDNA polymers based on the electrostatic adsorption, which directly resulted in the precipitation of (+)AuNPs and the decrease of (+)AuNPs absorption spectra. Under optimal conditions, miRNA-21 detection could be realized in the range of 20 pM-10 nM with a detection limit of 6.8 pM. In addition, (+)AuNPs used here are much more stable than commonly used negatively charged gold nanoparticles ((−)AuNPs) in mixed solution that contained salt, protein or other metal ions. Importantly, the assay could realize the detection of miRNA in human serum samples. PMID:27576601

  3. Search for S = +1 exotic baryon in the photon proton decaying to kaon-antikaon-positively charged pion (n) reaction

    NASA Astrophysics Data System (ADS)

    Guo, Lei

    The reaction gammap → pi+ k-k+ n has been investigated at Jefferson Lab using a tagged photon beam with an energy range of 3--5.47 GeV. A narrow baryon state with strangeness S = +1 and mass m = 1555 +/- 7 +/- 10 MeV/c 2 was observed in the nk+ invariant mass spectrum. The width of peak is consistent with the CLAS resolution (FWHM = 26 MeV/c2), and its statistical significance is 7.8 +/- 1.0 sigma. A baryon with positive strangeness has necessarily exotic structure and cannot be described in the framework of the naive constituent quark model. The signal is consistent with that predicted by a chiral soliton model for a 5-quark baryon state. Partial Wave Analysis was performed for the three-body mesonic background with the energy range of 4.8--5.47 GeV. The analysis demonstrates that the observed signal is unlikely to arise from meson production in the same final state. Interesting features were also observed in the 2-, 1- and 1 + partial wave intensity distributions. Due to the low statistics, the resonant nature of these meson waves is not determined.

  4. False Discovery Rate Estimation in Proteomics.

    PubMed

    Aggarwal, Suruchi; Yadav, Amit Kumar

    2016-01-01

    With the advancement in proteomics separation techniques and improvements in mass analyzers, the data generated in a mass-spectrometry based proteomics experiment is rising exponentially. Such voluminous datasets necessitate automated computational tools for high-throughput data analysis and appropriate statistical control. The data is searched using one or more of the several popular database search algorithms. The matches assigned by these tools can have false positives and statistical validation of these false matches is necessary before making any biological interpretations. Without such procedures, the biological inferences do not hold true and may be outright misleading. There is a considerable overlap between true and false positives. To control the false positives amongst a set of accepted matches, there is a need for some statistical estimate that can reflect the amount of false positives present in the data processed. False discovery rate (FDR) is the metric for global confidence assessment of a large-scale proteomics dataset. This chapter covers the basics of FDR, its application in proteomics, and methods to estimate FDR.

  5. Sleep deprivation and false memories.

    PubMed

    Frenda, Steven J; Patihis, Lawrence; Loftus, Elizabeth F; Lewis, Holly C; Fenn, Kimberly M

    2014-09-01

    Many studies have investigated factors that affect susceptibility to false memories. However, few have investigated the role of sleep deprivation in the formation of false memories, despite overwhelming evidence that sleep deprivation impairs cognitive function. We examined the relationship between self-reported sleep duration and false memories and the effect of 24 hr of total sleep deprivation on susceptibility to false memories. We found that under certain conditions, sleep deprivation can increase the risk of developing false memories. Specifically, sleep deprivation increased false memories in a misinformation task when participants were sleep deprived during event encoding, but did not have a significant effect when the deprivation occurred after event encoding. These experiments are the first to investigate the effect of sleep deprivation on susceptibility to false memories, which can have dire consequences.

  6. A Comparison between Students Who Receive and Who Do Not Receive a Writing Readiness Interventions on Handwriting Quality, Speed and Positive Reactions

    ERIC Educational Resources Information Center

    Lifshitz, Nirit; Har-Zvi, Shirley

    2015-01-01

    Proper acquisition of handwriting is required for success in school. This study compared the effects of two writing readiness interventions, "Traffic Light" and "Word and Sound" on kindergartners' handwriting quality, speed and positive reactions to writing. Handwriting readiness training for kindergarten children is…

  7. [Consensus position document on the child with an allergic reaction after vaccination or an allergy to vaccine components].

    PubMed

    Echeverría Zudaire, L; Ortigosa Del Castillo, L; Alonso Lebrero, E; Álvarez García, F J; Cortés Álvarez, N; García Sánchez, N; Martorell Aragonés, A

    2015-07-01

    Vaccinations are one of the main public health tools for the control of vaccine-preventable diseases. If a child is labeled to have had an allergic reaction to a vaccine, the next immunizations will probably be suspended in that child, with the risks involved in this decision. The rate of severe allergic reactions is very low, ranging between 0.5-1/100,000 doses. The causes of allergic reactions to vaccines, more than the vaccine itself, are often due to residual protein components in the manufacturing process, such as gelatin or egg, and rarely to yeast or latex. Most of vaccine reactions are mild, localized at the site of injection, but in some circumstances, severe anaphylactic reactions can occur. If an immediate-type allergic reaction is suspected when vaccinating, or a child allergic to some of the vaccine components has to be vaccinated, a correct diagnosis of the possible allergy has to be made. The usual components of each vaccine should be known, in order to determine if vaccination can be performed safely on the child. PMID:25648960

  8. [Consensus position document on the child with an allergic reaction after vaccination or an allergy to vaccine components].

    PubMed

    Echeverría Zudaire, L; Ortigosa Del Castillo, L; Alonso Lebrero, E; Álvarez García, F J; Cortés Álvarez, N; García Sánchez, N; Martorell Aragonés, A

    2015-07-01

    Vaccinations are one of the main public health tools for the control of vaccine-preventable diseases. If a child is labeled to have had an allergic reaction to a vaccine, the next immunizations will probably be suspended in that child, with the risks involved in this decision. The rate of severe allergic reactions is very low, ranging between 0.5-1/100,000 doses. The causes of allergic reactions to vaccines, more than the vaccine itself, are often due to residual protein components in the manufacturing process, such as gelatin or egg, and rarely to yeast or latex. Most of vaccine reactions are mild, localized at the site of injection, but in some circumstances, severe anaphylactic reactions can occur. If an immediate-type allergic reaction is suspected when vaccinating, or a child allergic to some of the vaccine components has to be vaccinated, a correct diagnosis of the possible allergy has to be made. The usual components of each vaccine should be known, in order to determine if vaccination can be performed safely on the child.

  9. Reduced False Memory after Sleep

    ERIC Educational Resources Information Center

    Fenn, Kimberly M.; Gallo, David A.; Margoliash, Daniel; Roediger, Henry L., III; Nusbaum, Howard C.

    2009-01-01

    Several studies have shown that sleep contributes to the successful maintenance of previously encoded information. This research has focused exclusively on memory for studied events, as opposed to false memories. Here we report three experiments showing that sleep reduces false memories in the Deese-Roediger-McDermott (DRM) memory illusion. False…

  10. False Belief vs. False Photographs: A Test of Theory of Mind or Working Memory?

    PubMed

    Callejas, Alicia; Shulman, Gordon L; Corbetta, Maurizio

    2011-01-01

    Theory of mind (ToM), the ability to reason about other people's thoughts and beliefs, has been traditionally studied in behavioral and neuroimaging experiments by comparing performance in "false belief" and "false photograph" (control) stories. However, some evidence suggests that these stories are not matched in difficulty, complicating the interpretation of results. Here, we more fully evaluated the relative difficulty of comprehending these stories and drawing inferences from them. Subjects read false belief and false photograph stories followed by comprehension questions that probed true ("reality" questions) or false beliefs ("representation" questions) appropriate to the stories. Stories and comprehension questions were read and answered, respectively, more slowly in the false photograph than false belief conditions, indicating their greater difficulty. Interestingly, accuracy on representation questions for false photograph stories was significantly lower than for all other conditions and correlated positively with participants' working memory span scores. These results suggest that drawing representational inferences from false photo stories is particularly difficult and places heavy demands on working memory. Extensive naturalistic practice with ToM reasoning may enable a more flexible and efficient mental representation of false belief stories, resulting in lower memory load requirements. An important implication of these results is that the differential modulation of right temporal-parietal junction (RTPJ) during ToM and "false photo" control conditions may reflect the documented negative correlation of RTPJ activity with working memory load rather than a specialized involvement in ToM processes.

  11. Executive Functioning and Preschoolers' Understanding of False Beliefs, False Photographs, and False Signs

    ERIC Educational Resources Information Center

    Sabbagh, Mark A.; Moses, Louis J.; Shiverick, Sean

    2006-01-01

    Two studies were conducted to investigate the specificity of the relationship between preschoolers' emerging executive functioning skills and false belief understanding. Study 1 (N=44) showed that 3- to 5-year-olds' performance on an executive functioning task that required selective suppression of actions predicted performance on false belief…

  12. Sleep deprivation and false confessions.

    PubMed

    Frenda, Steven J; Berkowitz, Shari R; Loftus, Elizabeth F; Fenn, Kimberly M

    2016-02-23

    False confession is a major contributor to the problem of wrongful convictions in the United States. Here, we provide direct evidence linking sleep deprivation and false confessions. In a procedure adapted from Kassin and Kiechel [(1996) Psychol Sci 7(3):125-128], participants completed computer tasks across multiple sessions and repeatedly received warnings that pressing the "Escape" key on their keyboard would cause the loss of study data. In their final session, participants either slept all night in laboratory bedrooms or remained awake all night. In the morning, all participants were asked to sign a statement, which summarized their activities in the laboratory and falsely alleged that they pressed the Escape key during an earlier session. After a single request, the odds of signing were 4.5 times higher for the sleep-deprived participants than for the rested participants. These findings have important implications and highlight the need for further research on factors affecting true and false confessions. PMID:26858426

  13. Sleep deprivation and false confessions.

    PubMed

    Frenda, Steven J; Berkowitz, Shari R; Loftus, Elizabeth F; Fenn, Kimberly M

    2016-02-23

    False confession is a major contributor to the problem of wrongful convictions in the United States. Here, we provide direct evidence linking sleep deprivation and false confessions. In a procedure adapted from Kassin and Kiechel [(1996) Psychol Sci 7(3):125-128], participants completed computer tasks across multiple sessions and repeatedly received warnings that pressing the "Escape" key on their keyboard would cause the loss of study data. In their final session, participants either slept all night in laboratory bedrooms or remained awake all night. In the morning, all participants were asked to sign a statement, which summarized their activities in the laboratory and falsely alleged that they pressed the Escape key during an earlier session. After a single request, the odds of signing were 4.5 times higher for the sleep-deprived participants than for the rested participants. These findings have important implications and highlight the need for further research on factors affecting true and false confessions.

  14. False positives from approved methods: Why and what to do

    SciTech Connect

    Lindsay, E.W.; Amano, R.M.

    1996-12-31

    With cleanups costing hundreds of thousands of dollars, it is imperative that one`s data show what is truly present. For the purpose of this presentation the authors will be concentrating on three types of analyses: volatiles, semivolatiles, and metals. For the volatiles they will concentrate on the analysis for benzene, toluene, ethylbenzene, and xylenes (BTEX) by EPA method 8020. For the semivolatiles they will concentrate on polynuclear aromatic hydrocarbons (PNAs) by EPA method 8310. The metals discussion will concentrate on the instrumentation used such as Inductively Coupled Plasma Mass Spectrometry (ICPMS), Graphite Furnace Atomic Absorption (GFAA), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP or ICPOES).

  15. The Problem of False Positives in Protein Marking Techniques

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Protein marking is a valuable technique in the study of insect movement in agriculture. It can be implemented on a large scale and is relatively inexpensive to use. Unlike other marking techniques, protein marking is a quantitative method. Whether an individual is considered marked or not is dependa...

  16. False-Positive Tangible Outcomes of Functional Analyses

    ERIC Educational Resources Information Center

    Rooker, Griffin W.; Iwata, Brian A.; Harper, Jill M.; Fahmie, Tara A.; Camp, Erin M.

    2011-01-01

    Functional analysis (FA) methodology is the most precise method for identifying variables that maintain problem behavior. Occasionally, however, results of an FA may be influenced by idiosyncratic sensitivity to aspects of the assessment conditions. For example, data from several studies suggest that inclusion of a tangible condition during an FA…

  17. Erasure Analyses: Reducing the Number of False Positives

    ERIC Educational Resources Information Center

    McClintock, Joseph Clair

    2015-01-01

    Erasure analysis is the study of the pattern or quantity of erasures on multiple-choice paper-and-pencil examinations, to determine whether erasures were made post-testing for the purpose of unfairly increasing students' scores. This study examined the erasure data from over 1.4 million exams, taken by more than 600,000 students. Three…

  18. False rape: a case report.

    PubMed

    Fanton, L; Schoendorff, P; Achache, P; Miras, A; Malicier, D

    1999-12-01

    A 16-year-old girl was admitted to the emergency department for sexual assault. The forensic examination revealed genital lesions of an age that were incompatible with her statements. She also presented extragenital lesions that resembled self-inflicted lesions. The reports of false rape allegations in the literature have all dealt with the motivations of the false victims. This case report is a reminder that an allegation of rape can be considered only on the basis of proof and not on speculation. PMID:10624933

  19. Evolutionary Psychology and False Confession

    ERIC Educational Resources Information Center

    Bering, Jesse M.; Shackelford, Todd K.

    2005-01-01

    This paper presents comments on Kassin's review, (see record 2005-03019-002) of the psychology of false confessions. The authors note that Kassin's review makes a compelling argument for the need for legal reform in police interrogation practices. Because his work strikes at the heart of the American criminal justice system--its fairness--the…

  20. Sleep deprivation and false confessions

    PubMed Central

    Frenda, Steven J.; Berkowitz, Shari R.; Loftus, Elizabeth F.; Fenn, Kimberly M.

    2016-01-01

    False confession is a major contributor to the problem of wrongful convictions in the United States. Here, we provide direct evidence linking sleep deprivation and false confessions. In a procedure adapted from Kassin and Kiechel [(1996) Psychol Sci 7(3):125–128], participants completed computer tasks across multiple sessions and repeatedly received warnings that pressing the “Escape” key on their keyboard would cause the loss of study data. In their final session, participants either slept all night in laboratory bedrooms or remained awake all night. In the morning, all participants were asked to sign a statement, which summarized their activities in the laboratory and falsely alleged that they pressed the Escape key during an earlier session. After a single request, the odds of signing were 4.5 times higher for the sleep-deprived participants than for the rested participants. These findings have important implications and highlight the need for further research on factors affecting true and false confessions. PMID:26858426

  1. Sleep Loss Produces False Memories

    PubMed Central

    Diekelmann, Susanne; Landolt, Hans-Peter; Lahl, Olaf; Born, Jan; Wagner, Ullrich

    2008-01-01

    People sometimes claim with high confidence to remember events that in fact never happened, typically due to strong semantic associations with actually encoded events. Sleep is known to provide optimal neurobiological conditions for consolidation of memories for long-term storage, whereas sleep deprivation acutely impairs retrieval of stored memories. Here, focusing on the role of sleep-related memory processes, we tested whether false memories can be created (a) as enduring memory representations due to a consolidation-associated reorganization of new memory representations during post-learning sleep and/or (b) as an acute retrieval-related phenomenon induced by sleep deprivation at memory testing. According to the Deese, Roediger, McDermott (DRM) false memory paradigm, subjects learned lists of semantically associated words (e.g., “night”, “dark”, “coal”,…), lacking the strongest common associate or theme word (here: “black”). Subjects either slept or stayed awake immediately after learning, and they were either sleep deprived or not at recognition testing 9, 33, or 44 hours after learning. Sleep deprivation at retrieval, but not sleep following learning, critically enhanced false memories of theme words. This effect was abolished by caffeine administration prior to retrieval, indicating that adenosinergic mechanisms can contribute to the generation of false memories associated with sleep loss. PMID:18946511

  2. Meningitis with polymerase chain reaction for varicella zoster positivity in cerebrospinal flid of a young immunocompetent adult

    PubMed Central

    Gupta, Pooja; Ranjan, Rajeev; Agrawal, C. S.; Muralikrishnan, K; Dave, Nikhil; Rana, Davinder Singh

    2016-01-01

    Meningitis caused by varicella zoster virus (VZV) is quite rare among young immunocompetent adults though immunocompromised patients are often seen to be affected by reactivation of VZV presenting with primary clinical features of dermatomal rashes and neurological sequelae. Here, we report the clinical scenario of a young, healthy male who had presented with fever, headache, and onset of dermatomal rashes later than the fever and was eventually diagnosed to be a case of VZV meningitis. We would like to highlight the fact that even young immunocompetent patients though rarely, might contract VZV meningitis and clinicians should have a high index of suspicion and keen eyes to catch the more obvious features of VZV infection on complete physical examination and must not harbor any reservations in ordering polymerase chain reaction for VZV DNA or initiating aggressive antiviral therapy.

  3. Meningitis with polymerase chain reaction for varicella zoster positivity in cerebrospinal flid of a young immunocompetent adult

    PubMed Central

    Gupta, Pooja; Ranjan, Rajeev; Agrawal, C. S.; Muralikrishnan, K; Dave, Nikhil; Rana, Davinder Singh

    2016-01-01

    Meningitis caused by varicella zoster virus (VZV) is quite rare among young immunocompetent adults though immunocompromised patients are often seen to be affected by reactivation of VZV presenting with primary clinical features of dermatomal rashes and neurological sequelae. Here, we report the clinical scenario of a young, healthy male who had presented with fever, headache, and onset of dermatomal rashes later than the fever and was eventually diagnosed to be a case of VZV meningitis. We would like to highlight the fact that even young immunocompetent patients though rarely, might contract VZV meningitis and clinicians should have a high index of suspicion and keen eyes to catch the more obvious features of VZV infection on complete physical examination and must not harbor any reservations in ordering polymerase chain reaction for VZV DNA or initiating aggressive antiviral therapy. PMID:27695246

  4. In vitro tests for drug hypersensitivity reactions: an ENDA/EAACI Drug Allergy Interest Group position paper.

    PubMed

    Mayorga, C; Celik, G; Rouzaire, P; Whitaker, P; Bonadonna, P; Rodrigues-Cernadas, J; Vultaggio, A; Brockow, K; Caubet, J C; Makowska, J; Nakonechna, A; Romano, A; Montañez, M I; Laguna, J J; Zanoni, G; Gueant, J L; Oude Elberink, H; Fernandez, J; Viel, S; Demoly, P; Torres, M J

    2016-08-01

    Drug hypersensitivity reactions (DHRs) are a matter of great concern, both for outpatient and in hospital care. The evaluation of these patients is complex, because in vivo tests have a suboptimal sensitivity and can be time-consuming, expensive and potentially risky, especially drug provocation tests. There are several currently available in vitro methods that can be classified into two main groups: those that help to characterize the active phase of the reaction and those that help to identify the culprit drug. The utility of these in vitro methods depends on the mechanisms involved, meaning that they cannot be used for the evaluation of all types of DHRs. Moreover, their effectiveness has not been defined by a consensus agreement between experts in the field. Thus, the European Network on Drug Allergy and Drug Allergy Interest Group of the European Academy of Allergy and Clinical Immunology has organized a task force to provide data and recommendations regarding the available in vitro methods for DHR diagnosis. We have found that although there are many in vitro tests, few of them can be given a recommendation of grade B or above mainly because there is a lack of well-controlled studies, most information comes from small studies with few subjects and results are not always confirmed in later studies. Therefore, it is necessary to validate the currently available in vitro tests in a large series of well-characterized patients with DHR and to develop new tests for diagnosis.

  5. Position-item associations play a role in the acquisition of order knowledge in an implicit serial reaction time task.

    PubMed

    Schuck, Nicolas W; Gaschler, Robert; Keisler, Aysha; Frensch, Peter A

    2012-03-01

    Knowledge of sequential regularities plays a key role in forms of explicit and implicit memory, such as working memory and motor skills. Despite important advances in the study of sequence knowledge in the past century, the theoretical development of implicit and explicit memory has occurred separately. Unlike the literature on implicit sequence learning, the explicit learning literature differentiates between 2 forms of representation of serial structure, chaining (C is the item following B in the sequence A-B-C-D) and ordinal position knowledge (C is the 3rd item). In 3 experiments, we demonstrate that these 2 forms of sequence knowledge can be acquired in implicit sequence learning. In Experiment 1, 2 trained sequences were recombined at transfer such that the strength of (a) associations between serial positions and sequence elements as well as (b) associations between successive sequence elements could be estimated. In Experiment 2, we compared sequence elements placed at the trained versus untrained serial position. Experiment 3 reduced cues that can be used to determine the start of a sequence within the stream of trials. Our results suggest that the discussion held in explicit memory research about different forms of representation of sequences knowledge also is relevant for implicit sequence learning.

  6. Risk factors associated with the presence of positive reactions in the SCCIT test in water buffalo around two cities in Punjab, Pakistan.

    PubMed

    Javed, M Tariq; Shahid, A Latif; Farooqi, Farooq A; Akhtar, M; Cardenas, Gabriel A; Wasiq, M; Cagiola, Monica

    2010-09-01

    The present study was undertaken to find out the association of certain risk factors with the positive SCCIT (single comparative cervical intradermal tuberculin) test in water buffaloes at Faisalabad and Okara, Pakistan. Seventy-six herds (697 buffaloes) at Faisalabad and 56 (395 buffaloes) at Okara were included in the study. The buffaloes were screened through SCCIT Test. Positive reaction to SCCIT test was recorded in 14% of herds and in 3% of buffaloes. The herds positive for this test were 18% when herds with less than 10 animals were excluded from the analysis and these were 19% when herds with less than 10 buffaloes were excluded. The results of logistic analysis (crude and adjusted) revealed the association of lactating status of buffaloes (OR=1.8) and the presence of cattle at the farm (OR=2-4) with positive SCCIT test. After controlling for the farm, the risk of a positive skin test was 1.5 times higher if we change the location of the animal. Similarly, the controlled analysis (for the farm, breed and other variables) revealed an increased risk (OR=1.1) of a positive skin test with the increase in cattle at the farm. The breed controlled stratified analysis showed the association of a number of cattle at the farm with a positive skin test. It can be concluded from the study that the prevalence of tuberculosis on the basis of a positive skin test is higher at herd level and lower at animal level. Further the risk of a positive skin test is higher when cattle are present at the farm.

  7. Outcome Knowledge and False Belief

    PubMed Central

    Ghrear, Siba E.; Birch, Susan A. J.; Bernstein, Daniel M.

    2016-01-01

    Virtually every social interaction involves reasoning about the perspectives of others, or ‘theory of mind (ToM).’ Previous research suggests that it is difficult to ignore our current knowledge when reasoning about a more naïve perspective (i.e., the curse of knowledge). In this Mini Review, we discuss the implications of the curse of knowledge for certain aspects of ToM. Particularly, we examine how the curse of knowledge influences key measurements of false belief reasoning. In closing, we touch on the need to develop new measurement tools to discern the mechanisms involved in the curse of knowledge and false belief reasoning, and how they develop across the lifespan. PMID:26903922

  8. [False innovations in clinical research].

    PubMed

    Garattini, Silvio; Bertele', Vittorio

    2006-11-01

    Pharmaceutical innovation is actually poorer than it seems, largely because of "false" innovations. Various factors help create an image of novelty in the pharmaceutical area. These factors act throughout the research and development process and in the post-marketing stages affecting the selection of study hypotheses, the adoption of the appropriate study methodology, and the interpretation and publication of results. Each of these steps may be diverted from the priority objective of patients' interest and shifted towards to the defence of the drugs companies' commercial interests. Regulators, NHS, physicians and patients must be vigilant to recognise and get rid of false innovations which can prevent the use of more effective and safer drugs and waste resources useful for effective treatments in other areas. Rewarding this lack of innovation discourages research for excellence and reduces the competitiveness of the pharmaceutical industry. PMID:17252717

  9. [False innovations in clinical research].

    PubMed

    Garattini, Silvio; Bertele', Vittorio

    2006-11-01

    Pharmaceutical innovation is actually poorer than it seems, largely because of "false" innovations. Various factors help create an image of novelty in the pharmaceutical area. These factors act throughout the research and development process and in the post-marketing stages affecting the selection of study hypotheses, the adoption of the appropriate study methodology, and the interpretation and publication of results. Each of these steps may be diverted from the priority objective of patients' interest and shifted towards to the defence of the drugs companies' commercial interests. Regulators, NHS, physicians and patients must be vigilant to recognise and get rid of false innovations which can prevent the use of more effective and safer drugs and waste resources useful for effective treatments in other areas. Rewarding this lack of innovation discourages research for excellence and reduces the competitiveness of the pharmaceutical industry.

  10. False advertising in the greenhouse?

    NASA Astrophysics Data System (ADS)

    Banse, K.

    1991-12-01

    Most scientists are convinced of the importance of their own research subjects. Broecker [1991] has deplored the temptation, if not the tendency, to go overboard and exaggerate this importance once funding enters the mind. In particular, he alleges inflated or even false claims by biological (and other) oceanographers regarding the relevance of their research to the "greenhouse effect," caused by the anthropogenic enhancement of the atmospheric CO2 content. He writes [Broecker, 1991, p. 191]: "In my estimation, on any list of subjects requiring intense study with regard to the prediction of the consequences of CO2 buildup in the atmosphere, I would place marine biological cycles near the bottom."

  11. 'Payson' Panorama in False Color

    NASA Technical Reports Server (NTRS)

    2006-01-01

    The panoramic camera aboard NASA's Mars Exploration Rover Opportunity acquired this panorama of the 'Payson' outcrop on the western edge of 'Erebus' Crater during Opportunity's sol 744 (Feb. 26, 2006). From this vicinity at the northern end of the outcrop, layered rocks are observed in the crater wall, which is about 1 meter (3.3 feet) thick. The view also shows rocks disrupted by the crater-forming impact event and subjected to erosion over time.

    To the left of the outcrop, a flat, thin layer of spherule-rich soils overlies more outcrop materials. The rover is currently traveling down this 'road' and observing the approximately 25-meter (82-foot) length of the outcrop prior to departing Erebus crater.

    The panorama camera took 28 separate exposures of this scene, using four different filters. The resulting panorama covers about 90 degrees of terrain around the rover. This false-color rendering was made using the camera's 753-nanometer, 535-nanometer and 423-nanometer filters. Using false color enhances the subtle color differences between layers of rocks and soils in the scene so that scientists can better analyze them. Image-to-image seams have been eliminated from the sky portion of the mosaic to better simulate the vista a person standing on Mars would see.

  12. Occult H. pylori infection partially explains ‘false-positive’ results of 13C-urea breath test

    PubMed Central

    Ramírez-Lázaro, María J; Lario, Sergio; Sánchez-Delgado, Jordi; Montserrat, Antònia; Quílez, Elisa M; Casalots, Alex; Suarez, David; Campo, Rafel; Brullet, Enric; Junquera, Félix; Sanfeliu, Isabel; Segura, Ferran

    2015-01-01

    Background In a previous study, UBiT-100 mg, (Otsuka, Spain), a commercial 13C-urea breath test omitting citric acid pre-treatment, had a high rate of false-positive results; however, it is possible that UBiT detected low-density ‘occult’ infection missed by other routine reference tests. We aimed to validate previous results in a new cohort and to rule out the possibility that false-positive UBiT were due to an ‘occult’ infection missed by reference tests. Methods Dyspeptic patients (n = 272) were prospectively enrolled and UBiT was performed, according to the manufacturer’s recommendations. Helicobacter pylori infection was determined by combining culture, histology and rapid urease test results. We calculated UBiT sensitivity, specificity, positive and negative predictive values (with 95% CI). In addition, we evaluated ‘occult’ H. pylori infection using two previously-validated polymerase chain reaction (PCR) methods for urease A (UreA) and 16 S sequences in gastric biopsies. We included 44 patients with a false-positive UBiT, and two control groups of 25 patients each, that were positive and negative for all H. pylori tests. Results UBiT showed a false-positive rate of 17%, with a specificity of 83%. All the positive controls and 12 of 44 patients (27%) with false-positive UBiT were positive for all two PCR tests; by contrast, none of our negative controls had two positive PCR tests. Conclusions UBiT suffers from a high rate of false-positive results and sub-optimal specificity, and the protocol skipping citric acid pre-treatment should be revised; however, low-density ‘occult’ H. pylori infection that was undetectable by conventional tests accounted for around 25% of the ‘false-positive’ results. PMID:26535122

  13. Moderate temperature sodium cells. V - Discharge reactions and rechargeability of NiS and NiS2 positive electrodes in molten NaAlCl4

    NASA Technical Reports Server (NTRS)

    Abraham, K. M.; Elliot, J. E.

    1984-01-01

    NiS2 and NiS have been characterized as high energy density rechargeable positive electrodes for moderate-temperature Na batteries of the configuration, Na(1)/beta double prime-Al2O3/NaAlCl4(1), NiSx. The batteries operate in the temperature range 170 - 190 C. Positive electrode reactions during discharge/charge cycles have been characterized. Excellent rechargeability of the batteries has been demonstrated by extended cell cycling. A Na/NiS2 cell, operating at 190 C, exceeded 600 deep discharge/charge cycles with practically no capacity deterioration. The feasibility of secondary Na/NiSx batteries with specific energies equal to or greater than 50 Wh/lb and cycle lifes exceeding 1000 deep discharge/charge cycles has been demonstrated.

  14. Cape Verde in False Color

    NASA Technical Reports Server (NTRS)

    2007-01-01

    A promontory nicknamed 'Cape Verde' can be seen jutting out from the walls of Victoria Crater in this false-color picture taken by the panoramic camera on NASA's Mars Exploration Rover Opportunity. The rover took this picture on martian day, or sol, 1329 (Oct. 20, 2007), more than a month after it began descending down the crater walls -- and just 9 sols shy of its second Martian birthday on sol 1338 (Oct. 29, 2007). Opportunity landed on the Red Planet on Jan. 25, 2004. That's nearly four years ago on Earth, but only two on Mars because Mars takes longer to travel around the sun than Earth. One Martian year equals 687 Earth days.

    This view was taken using three panoramic-camera filters, admitting light with wavelengths centered at 750 nanometers (near infrared), 530 nanometers (green) and 430 nanometers (violet).

  15. 23 CFR 635.119 - False statements.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ..., association, firm, or corporation, knowingly makes any false statement, false representation, or false report... submission of plans, maps, specifications, contracts, or costs of construction of any highway or...

  16. 23 CFR 635.119 - False statements.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ..., association, firm, or corporation, knowingly makes any false statement, false representation, or false report... submission of plans, maps, specifications, contracts, or costs of construction of any highway or...

  17. 23 CFR 635.119 - False statements.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., association, firm, or corporation, knowingly makes any false statement, false representation, or false report... submission of plans, maps, specifications, contracts, or costs of construction of any highway or...

  18. Drift and reactions of positive tetratomic ions in dry, atmospheric air: Their effects on the dynamics of primary and secondary streamers

    NASA Astrophysics Data System (ADS)

    Bekstein, A.; Yousfi, M.; Benhenni, M.; Ducasse, O.; Eichwald, O.

    2010-05-01

    The ion swarm data, namely, the reduced mobility, diffusion, and reaction rates of the positive tetratomic ions O4+ and N2O2+ in N2 and O2 have been determined from a Monte Carlo simulation using calculated and fitted elastic and inelastic cross sections. The elastic momentum transfer cross sections have been determined from a semiclassical Jeffreys-Wentzell-Kramers-Brilouin (JWKB) approximation based on a rigid core potential model well adapted for polyatomic ions. The inelastic cross sections have been approximated from considerations based on the N4+/O2 and N4+/N2 systems. The validated cross section sets in pure N2 and O2 have been used to determine the O4+ and N2O2+ swarm data in dry air over a large E/N range up to 1000 Td. However, due to the lack of experimental ion transport coefficients necessary for a more rigorous cross section validation, the present data, validated only at low E/N, should be regarded as a first approximation, susceptible to improvements as soon as measurements of ion transport coefficients become available in the literature. Then, the present data are used in a two-dimensional discharge dynamics fluid model for the simulation of the primary and secondary streamers for the case of a positive point-to-plane corona discharge in dry air. Relevant characteristics such as discharge current, charged particle densities, space charge electric field and the variation in active species like N and O radicals (very useful in many nonthermal plasma applications) are analyzed and discussed with and without the consideration of three positive tetratomic ions (N4+, O4+, and N2O2+). More particularly, the non-negligible effect of O4+, in the dynamics of the primary and secondary streamers during the discharge propagation and relaxation stages is highlighted with an emphasis on the role of the related kinetic reactions occurring between the different charged particles.

  19. Measurement of Internal Acyl Migration Reaction Kinetics Using Directly Coupled HPLC-NMR:  Application for the Positional Isomers of Synthetic (2-Fluorobenzoyl)-d-glucopyranuronic Acid.

    PubMed

    Sidelmann, U G; Hansen, S H; Gavaghan, C; Carless, H A; Lindon, J C; Farrant, R D; Wilson, I D; Nicholson, J K

    1996-08-01

    Ester glucuronides (1-O-acyl-β-d-glucopyranuronates) of many drugs may undergo internal acyl migration reactions, resulting in the formation of new positional isomers with both α- and β-anomers. We illustrate here a novel approach for the direct investigation of the acyl migration kinetics of ester glucuronides and show the application with respect to the isomers of synthetic (2-fluorobenzoyl)-d-glucopyranuronic acid. Individual isomers were separated from an equilibrium mixture containing the β-1-O-acyl, α- and β-2-O-acyl, α- and β-3-O-acyl, and α- and β-4-O-acyl isomers at pH 7.4 in 20 mM phosphate buffer. The interconverting isomers were separated using reversed-phase HPLC and pumped directly into a dedicated on-line NMR flow probe in a 600 MHz NMR spectrometer. The flow was stopped with each isomer in the NMR flow probe, and sequential NMR spectra were collected at 25 °C, allowing direct measurement of the production of positional isomers from each selectively isolated glucuronide isomer. All of the positional isomers and anomers were characterized, and relative quantities determined, and a kinetic model describing the rearrangement reactions was constructed. The acyl migration reaction kinetics were simulated using a theoretical approach using nine first-order rate constants determined for the acyl migration reactions and six first-order rate constants describing the mutarotation each of the 2-, 3-, and 4-positional isomers. The rate constants (in h(-)(1)) for the rearrangement reactions of the 2-fluorobenzoyl glucuronide isomers were as follows:  β-1-O-acyl, 0.29 ± 0.01; α-2-O-acyl, 0.11 ± 0.01; β-2-O-acyl, 0.07 ± 0.01; α-3-O-acyl, 0.10 ± 0.01; β-3-O-acyl, 0.09 ± 0.01; α-4-O-acyl, 0.09 ± 0.01; and β-4-O-acyl, 0.06 ± 0.01. The α- and β-anomerization rates were estimated on the basis of the kinetics model; the anomerization rates of the 4-O-acyl isomers were additionally determined experimentally using directly coupled HPLC-NMR. The

  20. White Rock in False Color

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    The THEMIS VIS camera is capable of capturing color images of the Martian surface using five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from using multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.

    This false color image shows the wind eroded deposit in Pollack Crater called 'White Rock'. This image was collected during the Southern Fall Season.

    Image information: VIS instrument. Latitude -8, Longitude 25.2 East (334.8 West). 0 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of

  1. Iani Chaos in False Color

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    The THEMIS VIS camera is capable of capturing color images of the Martian surface using five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from using multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.

    This false color image of a portion of the Iani Chaos region was collected during the Southern Fall season.

    Image information: VIS instrument. Latitude -2.6 Longitude 342.4 East (17.6 West). 36 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The

  2. Mimas Showing False Colors #2

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This false color image of Saturn's moon Mimas reveals variation in either the composition or texture across its surface.

    During its approach to Mimas on Aug. 2, 2005, the Cassini spacecraft narrow-angle camera obtained multi-spectral views of the moon from a range of 228,000 kilometers (142,500 miles).

    This image is a color composite of narrow-angle ultraviolet, green, infrared and clear filter images, which have been specially processed to accentuate subtle changes in the spectral properties of Mimas' surface materials. To create this view, three color images (ultraviolet, green and infrared) were combined with a single black and white picture that isolates and maps regional color differences to create the final product.

    Shades of blue and violet in the image at the right are used to identify surface materials that are bluer in color and have a weaker infrared brightness than average Mimas materials, which are represented by green.

    Herschel crater, a 140-kilometer-wide (88-mile) impact feature with a prominent central peak, is visible in the upper right of the image. The unusual bluer materials are seen to broadly surround Herschel crater. However, the bluer material is not uniformly distributed in and around the crater. Instead, it appears to be concentrated on the outside of the crater and more to the west than to the north or south. The origin of the color differences is not yet understood. It may represent ejecta material that was excavated from inside Mimas when the Herschel impact occurred. The bluer color of these materials may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil.

    This image was obtained when the Cassini spacecraft was above 25 degrees south, 134 degrees west latitude and longitude. The Sun-Mimas-spacecraft angle was 45 degrees and north is at the top.

    The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian

  3. Transition Metal Oxides for the Oxygen Reduction Reaction: Influence of the Oxidation States of the Metal and its Position on the Periodic Table.

    PubMed

    Toh, Rou Jun; Sofer, Zdeněk; Pumera, Martin

    2015-11-16

    Electrocatalysts have been developed to meet the needs and requirements of renewable energy applications. Metal oxides have been well explored and are promising for this purpose, however, many reports focus on only one or a few metal oxides at once. Herein, thirty metal oxides, which were either commercially available or synthesized by a simple and scalable method, were screened for comparison with regards to their electrocatalytic activity towards the oxygen reduction reaction (ORR). We show that although manganese, iron, cobalt, and nickel oxides generally displayed the ability to enhance the kinetics of oxygen reduction under alkaline conditions compared with bare glassy carbon, there is no significant correlation between the position of a metal on the periodic table and the electrocatalytic performance of its respective metal oxides. Moreover, it was also observed that mixed valent (+2, +3) oxides performed the poorest, compared with their respective pure metal oxides. These findings may be of paramount importance in the field of renewable energy. PMID:26351175

  4. Positive patch- and photopatch-test reactions to methylene bis-benzotriazolyl tetramethylbutylphenol in patients with both atopic dermatitis and chronic actinic dermatitis.

    PubMed

    Gonzalez, Mercedes E; Soter, Nicholas A; Cohen, David E

    2011-01-01

    Ultraviolet filters are the most common topical photoallergens. Although currently not available on the US market, methylene bis-benzotriazolyl tetramethylbutylphenol (referred to as bisoctrizole on product labels) represents a new class of UV filters that have both organic and inorganic properties and are widely available in different preparations in Europe, South America, and Asia. We report two patients with atopic dermatitis and chronic actinic dermatitis who had positive patch- and photopatch-test reactions, which suggested both an allergic contact and a photoallergic contact dermatitis from bisoctrizole. Neither patient could identify previous or current contact with the chemical; nonetheless, it is possible that either the allergic contact or photoallergic contact dermatitis from bisoctrizole led to their chronic actinic dermatitis.

  5. Transition Metal Oxides for the Oxygen Reduction Reaction: Influence of the Oxidation States of the Metal and its Position on the Periodic Table.

    PubMed

    Toh, Rou Jun; Sofer, Zdeněk; Pumera, Martin

    2015-11-16

    Electrocatalysts have been developed to meet the needs and requirements of renewable energy applications. Metal oxides have been well explored and are promising for this purpose, however, many reports focus on only one or a few metal oxides at once. Herein, thirty metal oxides, which were either commercially available or synthesized by a simple and scalable method, were screened for comparison with regards to their electrocatalytic activity towards the oxygen reduction reaction (ORR). We show that although manganese, iron, cobalt, and nickel oxides generally displayed the ability to enhance the kinetics of oxygen reduction under alkaline conditions compared with bare glassy carbon, there is no significant correlation between the position of a metal on the periodic table and the electrocatalytic performance of its respective metal oxides. Moreover, it was also observed that mixed valent (+2, +3) oxides performed the poorest, compared with their respective pure metal oxides. These findings may be of paramount importance in the field of renewable energy.

  6. Mimas Showing False Colors #1

    NASA Technical Reports Server (NTRS)

    2005-01-01

    False color images of Saturn's moon, Mimas, reveal variation in either the composition or texture across its surface.

    During its approach to Mimas on Aug. 2, 2005, the Cassini spacecraft narrow-angle camera obtained multi-spectral views of the moon from a range of 228,000 kilometers (142,500 miles).

    The image at the left is a narrow angle clear-filter image, which was separately processed to enhance the contrast in brightness and sharpness of visible features. The image at the right is a color composite of narrow-angle ultraviolet, green, infrared and clear filter images, which have been specially processed to accentuate subtle changes in the spectral properties of Mimas' surface materials. To create this view, three color images (ultraviolet, green and infrared) were combined into a single black and white picture that isolates and maps regional color differences. This 'color map' was then superimposed over the clear-filter image at the left.

    The combination of color map and brightness image shows how the color differences across the Mimas surface materials are tied to geological features. Shades of blue and violet in the image at the right are used to identify surface materials that are bluer in color and have a weaker infrared brightness than average Mimas materials, which are represented by green.

    Herschel crater, a 140-kilometer-wide (88-mile) impact feature with a prominent central peak, is visible in the upper right of each image. The unusual bluer materials are seen to broadly surround Herschel crater. However, the bluer material is not uniformly distributed in and around the crater. Instead, it appears to be concentrated on the outside of the crater and more to the west than to the north or south. The origin of the color differences is not yet understood. It may represent ejecta material that was excavated from inside Mimas when the Herschel impact occurred. The bluer color of these materials may be caused by subtle differences in

  7. Humoural immune response and pathological analysis in patients with false immune diagnosis of cystic echinococcosis

    PubMed Central

    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

  8. Comparative Analysis of Real-Time Polymerase Chain Reaction Methods to Typing HLA-B*57:01 in HIV-1-Positive Patients

    PubMed Central

    Falasca, Francesca; Russo, Cinzia Dello; Mora, Barbara; Pirazzoli, Antonella; Fantauzzi, Alessandra; Navarra, Pierluigi; Pizzuti, Antonio; De Vito, Corrado; Antonelli, Guido

    2016-01-01

    Abstract The HLA-B*57:01 allele is strongly associated with the hypersensitivity reaction to Abacavir (ABC). Therefore, treatment guidelines recommend that patients initiating ABC are preventively tested for the presence of this allele. To date, four different commercial assays based on the real-time quantitative polymerase chain reaction (Q-PCR) technique are available for the detection of HLA-B*57:01: Duplicα-RealTime Reagent Set HLA-B*57:01 by Euroclone, HLA-B*57:01 Real-TM by Sacace Biotechnologies, COBAS AmpliPrep/COBAS TaqMan HLA-B*57:01 Screening Test by Roche Diagnostic, and HLA-B*57:01 by Nuclear Laser Medicine. The study was carried out to compare the performance of the first three commercially available Q-PCR kits in a routine clinical setting. A total of 98 samples from Policlinico Umberto I Hospital were tested. Results obtained by the Duplicα-RealTime Genotyping kit and AmpliPrep/TaqMan system were 100% concordant. In contrast, genotyping by the HLA-B*57:01 Real-TM kit showed poor agreement with the other systems, that is, 12 out of 33 positive samples were detected as HLA-B*57:01 negative. To confirm the correct genotype of these discordant samples, two additional methods with rapid turnaround times and already implemented into routine clinical practice were used, that is, a PCR-based microsequence-specific primer DNA typing test and a laboratory-developed screening test in Q-PCR. All 12 discordant samples were genotyped as HLA-B*57:01-positive samples using these two additional methods in a single-blinded manner, thus confirming the low sensitivity of HLA-B*57:01 Real-TM test. These findings underline the need to compare results obtained with commercial assays before choosing a test suitable for use in a routine clinical laboratory. PMID:26750774

  9. Comparative Analysis of Real-Time Polymerase Chain Reaction Methods to Typing HLA-B*57:01 in HIV-1-Positive Patients.

    PubMed

    Falasca, Francesca; Dello Russo, Cinzia; Mora, Barbara; Pirazzoli, Antonella; Fantauzzi, Alessandra; Navarra, Pierluigi; Pizzuti, Antonio; De Vito, Corrado; Antonelli, Guido; Turriziani, Ombretta

    2016-07-01

    The HLA-B*57:01 allele is strongly associated with the hypersensitivity reaction to Abacavir (ABC). Therefore, treatment guidelines recommend that patients initiating ABC are preventively tested for the presence of this allele. To date, four different commercial assays based on the real-time quantitative polymerase chain reaction (Q-PCR) technique are available for the detection of HLA-B*57:01: Duplicα-RealTime Reagent Set HLA-B*57:01 by Euroclone, HLA-B*57:01 Real-TM by Sacace Biotechnologies, COBAS AmpliPrep/COBAS TaqMan HLA-B*57:01 Screening Test by Roche Diagnostic, and HLA-B*57:01 by Nuclear Laser Medicine. The study was carried out to compare the performance of the first three commercially available Q-PCR kits in a routine clinical setting. A total of 98 samples from Policlinico Umberto I Hospital were tested. Results obtained by the Duplicα-RealTime Genotyping kit and AmpliPrep/TaqMan system were 100% concordant. In contrast, genotyping by the HLA-B*57:01 Real-TM kit showed poor agreement with the other systems, that is, 12 out of 33 positive samples were detected as HLA-B*57:01 negative. To confirm the correct genotype of these discordant samples, two additional methods with rapid turnaround times and already implemented into routine clinical practice were used, that is, a PCR-based microsequence-specific primer DNA typing test and a laboratory-developed screening test in Q-PCR. All 12 discordant samples were genotyped as HLA-B*57:01-positive samples using these two additional methods in a single-blinded manner, thus confirming the low sensitivity of HLA-B*57:01 Real-TM test. These findings underline the need to compare results obtained with commercial assays before choosing a test suitable for use in a routine clinical laboratory. PMID:26750774

  10. Mood-congruent true and false memory: effects of depression.

    PubMed

    Howe, Mark L; Malone, Catherine

    2011-02-01

    The Deese/Roediger-McDermott paradigm was used to investigate the effect of depression on true and false recognition. In this experiment true and false recognition was examined across positive, neutral, negative, and depression-relevant lists for individuals with and without a diagnosis of major depressive disorder. Results showed that participants with major depressive disorder falsely recognised significantly more depression-relevant words than non-depressed controls. These findings also parallel recent research using recall instead of recognition and show that there are clear mood congruence effects for depression on false memory performance.

  11. 19 CFR 111.32 - False information.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false False information. 111.32 Section 111.32 Customs... CUSTOMS BROKERS Duties and Responsibilities of Customs Brokers § 111.32 False information. A broker must... procure the giving of, any false or misleading information or testimony in any matter pending before...

  12. Economic evaluation of 21-gene reverse transcriptase-polymerase chain reaction assay in lymph-node-negative, estrogen-receptor-positive, early-stage breast cancer in Japan.

    PubMed

    Kondo, Masahide; Hoshi, Shu Ling; Ishiguro, Hiroshi; Yoshibayashi, Hiroshi; Toi, Masakazu

    2008-11-01

    The 21-gene reverse transcriptase-polymerase chain reaction assay with a patented algorithm is validated as a good predictor of prognosis and potential benefit from adjuvant chemotherapy for lymph-node-negative, estrogen-receptor-positive, early-stage breast cancer, while its high cost raises concern about how to finance it. Cost-effectiveness analysis comparing prevalent National Comprehensive Cancer Network (NCCN) guideline/St Gallen recommendation-guided treatment with the assay-guided treatment is carried out with budget impact estimation in the context of Japan's health care system. Incremental cost-effectiveness ratios are estimated as 2,997,495 yen/QALY (26,065 US$/QALY) in the comparison between NCCN guided-treatment vs. the assay-guided treatment, and as 1,239,055 yen/QALY (10,774 US$/QALY) in the comparison between St Gallen guided-treatment vs. the assay-guided treatment. Budget impact is estimated as yen2,638 million (US$23 million) to yen3,225 million (US$28 million) per year. The routine use of the assay is indicated as cost-effective. And the budget impact could be judged as within fundable level. PMID:18075786

  13. The false classification of extinction risk in noisy environments

    PubMed Central

    Connors, B. M.; Cooper, A. B.; Peterman, R. M.; Dulvy, N. K.

    2014-01-01

    Abundance trends are the basis for many classifications of threat and recovery status, but they can be a challenge to interpret because of observation error, stochastic variation in abundance (process noise) and temporal autocorrelation in that process noise. To measure the frequency of incorrectly detecting a decline (false-positive or false alarm) and failing to detect a true decline (false-negative), we simulated stable and declining abundance time series across several magnitudes of observation error and autocorrelated process noise. We then empirically estimated the magnitude of observation error and autocorrelated process noise across a broad range of taxa and mapped these estimates onto the simulated parameter space. Based on the taxa we examined, at low classification thresholds (30% decline in abundance) and short observation windows (10 years), false alarms would be expected to occur, on average, about 40% of the time assuming density-independent dynamics, whereas false-negatives would be expected to occur about 60% of the time. However, false alarms and failures to detect true declines were reduced at higher classification thresholds (50% or 80% declines), longer observation windows (20, 40, 60 years), and assuming density-dependent dynamics. The lowest false-positive and false-negative rates are likely to occur for large-bodied, long-lived animal species. PMID:24898368

  14. An Association Account of False Belief Understanding

    ERIC Educational Resources Information Center

    De Bruin, L. C.; Newen, A.

    2012-01-01

    The elicited-response false belief task has traditionally been considered as reliably indicating that children acquire an understanding of false belief around 4 years of age. However, recent investigations using spontaneous-response tasks suggest that false belief understanding emerges much earlier. This leads to a developmental paradox: if young…

  15. 30 CFR 281.5 - False statements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false False statements. 281.5 Section 281.5 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF MINERALS OTHER THAN OIL, GAS, AND SULPHUR IN THE OUTER CONTINENTAL SHELF General § 281.5 False statements. Under...

  16. 43 CFR 3000.2 - False statements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) MINERALS MANAGEMENT: GENERAL General § 3000.2 False statements. Under the provisions of 18 U.S.C. 1001, it is a crime punishable by 5 years imprisonment or a... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false False statements. 3000.2 Section...

  17. Attitude Importance and the False Consensus Effect.

    ERIC Educational Resources Information Center

    Fabrigar, Leandre R.; Krosnick, Jon A.

    1995-01-01

    Explores the possibility that importance may regulate the magnitude of the false consensus effect. Analysis revealed a strong false consensus effect but no reliable relation between its magnitude and attitude importance. Results contradict assumptions that the false consensus effect arises from attitudes that directly or indirectly influence…

  18. 20 CFR 356.3 - False claims.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 20 Employees' Benefits 1 2012-04-01 2012-04-01 false False claims. 356.3 Section 356.3 Employees' Benefits RAILROAD RETIREMENT BOARD ADMINISTRATIVE REMEDIES FOR FRAUDULENT CLAIMS OR STATEMENTS CIVIL MONETARY PENALTY INFLATION ADJUSTMENT § 356.3 False claims. In the case of penalties assessed under 31...

  19. 20 CFR 356.3 - False claims.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false False claims. 356.3 Section 356.3 Employees' Benefits RAILROAD RETIREMENT BOARD ADMINISTRATIVE REMEDIES FOR FRAUDULENT CLAIMS OR STATEMENTS CIVIL MONETARY PENALTY INFLATION ADJUSTMENT § 356.3 False claims. In the case of penalties assessed under 31...

  20. 20 CFR 356.3 - False claims.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 20 Employees' Benefits 1 2011-04-01 2011-04-01 false False claims. 356.3 Section 356.3 Employees' Benefits RAILROAD RETIREMENT BOARD ADMINISTRATIVE REMEDIES FOR FRAUDULENT CLAIMS OR STATEMENTS CIVIL MONETARY PENALTY INFLATION ADJUSTMENT § 356.3 False claims. In the case of penalties assessed under 31...

  1. False-lock performance improvement in Costas loops

    NASA Astrophysics Data System (ADS)

    Makarios, A. H.; Tozer, T. C.

    1982-10-01

    A technique is described to reduce the probability of false-lock in Costas loops. This is where a frequency offset arises at a multiple of half the incoming data rate due to finite bandwidth of the arm filters. A modification is described to process components of this offset so as to augment the feedback control voltage. The performance is analyzed and it is shown how certain false-lock positions may be avoided.

  2. An association account of false belief understanding.

    PubMed

    De Bruin, L C; Newen, A

    2012-05-01

    The elicited-response false belief task has traditionally been considered as reliably indicating that children acquire an understanding of false belief around 4 years of age. However, recent investigations using spontaneous-response tasks suggest that false belief understanding emerges much earlier. This leads to a developmental paradox: if young infants already understand false belief, then why do they fail the elicited-response false belief task? We postulate two systems to account for the development of false belief understanding: an association module, which provides infants with the capacity to register congruent associations between agents and objects, and an operating system, which allows them to transform these associations into incongruent associations through a process of inhibition, selection and representation. The interaction between the association module and the operating system enables infants to register increasingly complex associations on the basis of another agent's movements, visual perspective and propositional attitudes. This allows us account for the full range of findings on false belief understanding.

  3. 19 CFR 11.13 - False designations of origin and false descriptions; false marking of articles of gold or silver.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... descriptions; false marking of articles of gold or silver. 11.13 Section 11.13 Customs Duties U.S. CUSTOMS AND... gold or silver. (a) Articles which bear, or the containers which bear, false designations of origin, or.... 1405q, and shall be detained. (b) Articles made in whole or in part of gold or silver or alloys...

  4. 19 CFR 11.13 - False designations of origin and false descriptions; false marking of articles of gold or silver.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... descriptions; false marking of articles of gold or silver. 11.13 Section 11.13 Customs Duties U.S. CUSTOMS AND... gold or silver. (a) Articles which bear, or the containers which bear, false designations of origin, or.... 1405q, and shall be detained. (b) Articles made in whole or in part of gold or silver or alloys...

  5. 19 CFR 11.13 - False designations of origin and false descriptions; false marking of articles of gold or silver.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... descriptions; false marking of articles of gold or silver. 11.13 Section 11.13 Customs Duties U.S. CUSTOMS AND... gold or silver. (a) Articles which bear, or the containers which bear, false designations of origin, or.... 1405q, and shall be detained. (b) Articles made in whole or in part of gold or silver or alloys...

  6. 19 CFR 11.13 - False designations of origin and false descriptions; false marking of articles of gold or silver.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... descriptions; false marking of articles of gold or silver. 11.13 Section 11.13 Customs Duties U.S. CUSTOMS AND... gold or silver. (a) Articles which bear, or the containers which bear, false designations of origin, or.... 1405q, and shall be detained. (b) Articles made in whole or in part of gold or silver or alloys...

  7. 19 CFR 11.13 - False designations of origin and false descriptions; false marking of articles of gold or silver.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... descriptions; false marking of articles of gold or silver. 11.13 Section 11.13 Customs Duties U.S. CUSTOMS AND... gold or silver. (a) Articles which bear, or the containers which bear, false designations of origin, or.... 1405q, and shall be detained. (b) Articles made in whole or in part of gold or silver or alloys...

  8. False confessions: causes, consequences, and implications.

    PubMed

    Leo, Richard A

    2009-01-01

    In the past two decades, hundreds of convicted prisoners have been exonerated by DNA and non-DNA evidence, revealing that police-induced false confessions are a leading cause of wrongful conviction of the innocent. In this article, empirical research on the causes and correlates of false confessions is reviewed. After a description of the three sequential processes that are responsible for the elicitation of false confessions--misclassification, coercion, and contamination--the three psychologically distinct types of false confession (voluntary, compliant, and persuaded) are discussed along with the consequences of introducing false-confession evidence in the criminal justice system. The article concludes with a brief discussion of the implications of empirical research for reducing the number of false confessions and improving the accuracy of confession evidence that is introduced against a defendant at trial. PMID:19767498

  9. Constructing rich false memories of committing crime.

    PubMed

    Shaw, Julia; Porter, Stephen

    2015-03-01

    Memory researchers long have speculated that certain tactics may lead people to recall crimes that never occurred, and thus could potentially lead to false confessions. This is the first study to provide evidence suggesting that full episodic false memories of committing crime can be generated in a controlled experimental setting. With suggestive memory-retrieval techniques, participants were induced to generate criminal and noncriminal emotional false memories, and we compared these false memories with true memories of emotional events. After three interviews, 70% of participants were classified as having false memories of committing a crime (theft, assault, or assault with a weapon) that led to police contact in early adolescence and volunteered a detailed false account. These reported false memories of crime were similar to false memories of noncriminal events and to true memory accounts, having the same kinds of complex descriptive and multisensory components. It appears that in the context of a highly suggestive interview, people can quite readily generate rich false memories of committing crime. PMID:25589599

  10. Constructing rich false memories of committing crime.

    PubMed

    Shaw, Julia; Porter, Stephen

    2015-03-01

    Memory researchers long have speculated that certain tactics may lead people to recall crimes that never occurred, and thus could potentially lead to false confessions. This is the first study to provide evidence suggesting that full episodic false memories of committing crime can be generated in a controlled experimental setting. With suggestive memory-retrieval techniques, participants were induced to generate criminal and noncriminal emotional false memories, and we compared these false memories with true memories of emotional events. After three interviews, 70% of participants were classified as having false memories of committing a crime (theft, assault, or assault with a weapon) that led to police contact in early adolescence and volunteered a detailed false account. These reported false memories of crime were similar to false memories of noncriminal events and to true memory accounts, having the same kinds of complex descriptive and multisensory components. It appears that in the context of a highly suggestive interview, people can quite readily generate rich false memories of committing crime.

  11. How Does Distinctive Processing Reduce False Recall?

    ERIC Educational Resources Information Center

    Hunt, R. Reed; Smith, Rebekah E.; Dunlap, Kathryn R.

    2011-01-01

    False memories arising from associatively related lists are a robust phenomenon that resists many efforts to prevent it. However, a few variables have been shown to reduce this form of false memory. Explanations for how the reduction is accomplished have focused on either output monitoring processes or constraints on access, but neither idea alone…

  12. 49 CFR 234.107 - False activation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., DEPARTMENT OF TRANSPORTATION GRADE CROSSING SAFETY, INCLUDING SIGNAL SYSTEMS, STATE ACTION PLANS, AND... Grade Crossings § 234.107 False activation. Upon receipt of a credible report of a false activation, a railroad having maintenance responsibility for the highway-rail grade crossing warning system...

  13. 49 CFR 234.107 - False activation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., DEPARTMENT OF TRANSPORTATION GRADE CROSSING SAFETY, INCLUDING SIGNAL SYSTEMS, STATE ACTION PLANS, AND... Grade Crossings § 234.107 False activation. Upon receipt of a credible report of a false activation, a railroad having maintenance responsibility for the highway-rail grade crossing warning system...

  14. 49 CFR 234.107 - False activation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ..., DEPARTMENT OF TRANSPORTATION GRADE CROSSING SAFETY, INCLUDING SIGNAL SYSTEMS, STATE ACTION PLANS, AND... Grade Crossings § 234.107 False activation. Upon receipt of a credible report of a false activation, a railroad having maintenance responsibility for the highway-rail grade crossing warning system...

  15. 30 CFR 281.5 - False statements.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false False statements. 281.5 Section 281.5 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF MINERALS OTHER THAN OIL, GAS, AND SULPHUR IN THE OUTER CONTINENTAL SHELF General §...

  16. 15 CFR 80.6 - False statements.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 15 Commerce and Foreign Trade 1 2011-01-01 2011-01-01 false False statements. 80.6 Section 80.6 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade BUREAU OF THE CENSUS, DEPARTMENT OF COMMERCE FURNISHING PERSONAL CENSUS DATA FROM CENSUS OF POPULATION SCHEDULES § 80.6...

  17. 15 CFR 80.6 - False statements.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 15 Commerce and Foreign Trade 1 2013-01-01 2013-01-01 false False statements. 80.6 Section 80.6 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade BUREAU OF THE CENSUS, DEPARTMENT OF COMMERCE FURNISHING PERSONAL CENSUS DATA FROM CENSUS OF POPULATION SCHEDULES § 80.6...

  18. 15 CFR 80.6 - False statements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 15 Commerce and Foreign Trade 1 2012-01-01 2012-01-01 false False statements. 80.6 Section 80.6 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade BUREAU OF THE CENSUS, DEPARTMENT OF COMMERCE FURNISHING PERSONAL CENSUS DATA FROM CENSUS OF POPULATION SCHEDULES § 80.6...

  19. 15 CFR 80.6 - False statements.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 15 Commerce and Foreign Trade 1 2014-01-01 2014-01-01 false False statements. 80.6 Section 80.6 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade BUREAU OF THE CENSUS, DEPARTMENT OF COMMERCE FURNISHING PERSONAL CENSUS DATA FROM CENSUS OF POPULATION SCHEDULES § 80.6...

  20. 15 CFR 80.6 - False statements.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false False statements. 80.6 Section 80.6 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade BUREAU OF THE CENSUS, DEPARTMENT OF COMMERCE FURNISHING PERSONAL CENSUS DATA FROM CENSUS OF POPULATION SCHEDULES § 80.6...

  1. Can False Memories Prime Problem Solutions?

    ERIC Educational Resources Information Center

    Howe, Mark L.; Garner, Sarah R.; Dewhurst, Stephen A.; Ball, Linden J.

    2010-01-01

    Previous research has suggested that false memories can prime performance on related implicit and explicit memory tasks. The present research examined whether false memories can also be used to prime higher order cognitive processes, namely, insight-based problem solving. Participants were asked to solve a number of compound remote associate task…

  2. Explaining the Development of False Memories.

    ERIC Educational Resources Information Center

    Reyna, Valerie F.; Holliday, Robyn; Marche, Tammy

    2002-01-01

    Reviews explanatory dimensions of children's false memory relevant to forensic practice: measurement, development, social factors, individual differences, varieties of memories and memory judgments, and varieties of procedures inducing false memories. Asserts that recent studies fail to use techniques that separate acquiescence from memory…

  3. 20 CFR 356.3 - False claims.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 20 Employees' Benefits 1 2014-04-01 2012-04-01 true False claims. 356.3 Section 356.3 Employees' Benefits RAILROAD RETIREMENT BOARD ADMINISTRATIVE REMEDIES FOR FRAUDULENT CLAIMS OR STATEMENTS CIVIL MONETARY PENALTY INFLATION ADJUSTMENT § 356.3 False claims. In the case of penalties assessed under 31...

  4. 20 CFR 356.3 - False claims.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 20 Employees' Benefits 1 2013-04-01 2012-04-01 true False claims. 356.3 Section 356.3 Employees' Benefits RAILROAD RETIREMENT BOARD ADMINISTRATIVE REMEDIES FOR FRAUDULENT CLAIMS OR STATEMENTS CIVIL MONETARY PENALTY INFLATION ADJUSTMENT § 356.3 False claims. In the case of penalties assessed under 31...

  5. The consequences of suggesting false childhood food events.

    PubMed

    Bernstein, Daniel M; Scoboria, Alan; Arnold, Robert

    2015-03-01

    We combined data across eight published experiments (N=1369) to examine the formation and consequences of false autobiographical beliefs and memories. Our path models revealed that the formation of false autobiographical belief fully mediated the pathway between suggesting to people that they had experienced a positive or negative food-related event in the past and current preference for that food. Suggestion indirectly affected intention to eat the food via change in autobiographical belief. The development of belief with and without memory produced similar changes in food preferences and behavior intention, indicating that belief in the event drives changes in suggestion-related attitudes. Finally, positive suggestions (e.g., "you loved asparagus the first time you tried it") yielded stronger effects than negative suggestions (e.g., "you got sick eating egg salad"). These findings show that false autobiographical suggestions lead to the development of autobiographical beliefs, which in turn, have consequences for one's attitudes and behaviors. PMID:25613303

  6. Blocking Mimicry Makes True and False Smiles Look the Same

    PubMed Central

    Rychlowska, Magdalena; Cañadas, Elena; Wood, Adrienne; Krumhuber, Eva G.; Fischer, Agneta; Niedenthal, Paula M.

    2014-01-01

    Recent research suggests that facial mimicry underlies accurate interpretation of subtle facial expressions. In three experiments, we manipulated mimicry and tested its role in judgments of the genuineness of true and false smiles. Experiment 1 used facial EMG to show that a new mouthguard technique for blocking mimicry modifies both the amount and the time course of facial reactions. In Experiments 2 and 3, participants rated true and false smiles either while wearing mouthguards or when allowed to freely mimic the smiles with or without additional distraction, namely holding a squeeze ball or wearing a finger-cuff heart rate monitor. Results showed that blocking mimicry compromised the decoding of true and false smiles such that they were judged as equally genuine. Together the experiments highlight the role of facial mimicry in judging subtle meanings of facial expressions. PMID:24670316

  7. Blocking mimicry makes true and false smiles look the same.

    PubMed

    Rychlowska, Magdalena; Cañadas, Elena; Wood, Adrienne; Krumhuber, Eva G; Fischer, Agneta; Niedenthal, Paula M

    2014-01-01

    Recent research suggests that facial mimicry underlies accurate interpretation of subtle facial expressions. In three experiments, we manipulated mimicry and tested its role in judgments of the genuineness of true and false smiles. Experiment 1 used facial EMG to show that a new mouthguard technique for blocking mimicry modifies both the amount and the time course of facial reactions. In Experiments 2 and 3, participants rated true and false smiles either while wearing mouthguards or when allowed to freely mimic the smiles with or without additional distraction, namely holding a squeeze ball or wearing a finger-cuff heart rate monitor. Results showed that blocking mimicry compromised the decoding of true and false smiles such that they were judged as equally genuine. Together the experiments highlight the role of facial mimicry in judging subtle meanings of facial expressions.

  8. Teacher Education and the Enduring Significance of "False Empathy"

    ERIC Educational Resources Information Center

    Warren, Chezare A.; Hotchkins, Bryan K.

    2015-01-01

    The concept "False Empathy" posited by critical race theory luminary Richard Delgado ("Calif Law Rev" 84(1):61-100, 1996) easily obscures White teacher's good intentions to be effective educators of racially, culturally, and linguistically diverse students. It is argued here that critical race theory is useful for isolating and…

  9. Siblings, Language, and False Belief in Low-Income Children

    ERIC Educational Resources Information Center

    Tompkins, Virginia; Farrar, M. Jeffrey; Guo, Ying

    2013-01-01

    The authors examined the relationship between number of siblings and false belief understanding (FBU) in 94 low-income 4-5-year-olds. Previous research with middle-income children has shown a positive association between number of siblings and FBU. However, it is unclear whether having multiple siblings in low-income families is related to better…

  10. Controlling false discoveries in genetic studies.

    PubMed

    van den Oord, Edwin J C G

    2008-07-01

    A false discovery occurs when a researcher concludes that a marker is involved in the etiology of the disease whereas in reality it is not. In genetic studies the risk of false discoveries is very high because only few among the many markers that can be tested will have an effect on the disease. In this article, we argue that it may be best to use methods for controlling false discoveries that would introduce the same ratio of false discoveries divided by all rejected tests into the literature regardless of systematic differences between studies. After a brief discussion of traditional "multiple testing" methods, we show that methods that control the false discovery rate (FDR) may be more suitable to achieve this goal. These FDR methods are therefore discussed in more detail. Instead of merely testing for main effects, it may be important to search for gene-environment/covariate interactions, gene-gene interactions or genetic variants affecting disease subtypes. In the second section, we point out the challenges involved in controlling false discoveries in such searches. The final section discusses the role of replication studies for eliminating false discoveries and the complexities associated with the definition of what constitutes a replication and the design of these studies.

  11. The False Claims Act and clinical laboratories.

    PubMed

    Vogel, R L

    1993-01-01

    In its efforts to fight fraud, the government has turned increasingly to the civil False Claims Act. The Act imposes triple damages plus monetary penalties against those who defraud the federal government. The Act also encourages whistleblowers to report fraud by offering the prospect of large bounties. This article describes the False Claims Act, its qui tam provision dealing with whistleblowers, and the application of the Act to clinical laboratories.

  12. Review article: the false-bottom ice

    NASA Astrophysics Data System (ADS)

    Alexandrov, D. V.; Jouzel, J.; Nizovtseva, I.; Ryashko, L. B.

    2013-11-01

    Nansen from his observations in the Beaufort Sea published in 1897 noted that heat transfer from the fresh water (with a~temperature of 0 °C) to the arctic salt water (with a temperature of -1.6 °C) is the only source of ice accretion during the polar summer. This transfer mechanism, unusual at first sight, is responsible for the initiation and evolution of a false bottom ice, changing ice properties to a great extent and affecting various processes while interacting with the ocean and the atmosphere. The processes of false bottom ice growth from below (i.e. from the ocean to the atmosphere) become of prime importance in the era of global warming and climate change. In this review, we summarize the theoretical approaches, field and laboratory observations, conducted during more than 100 yr, in order to address the problem of false bottoms to a broad community of readers. We also discuss the recent modeling advances to which we have contributed. A "false bottom" is a thin layer of ice which forms in summer underneath the floe, where fresh water lies between the salt water and the ice. Such false bottoms represent the only significant source of ice growth in the Arctic during the spring-summer period. Their evolution influences the mass balance of the Arctic sea-ice cover, which is recognized as an indicator of climate change. However, the quantity, aerial extent and other properties of false bottoms are difficult to measure because coring under the surface melt ponds leads to direct mixing of surface and under-ice water. This explains why their aerial extent and overall volume is still not known despite the fact that the upper limit of the present-day estimate of the false bottom ice coverage is approximately half of the sea ice surface. The growth of false bottoms also leads to other important consequences for various physical, chemical and biological processes associated with their dynamics.

  13. Do 15-Month-Old Infants Understand False Beliefs?

    PubMed Central

    Onishi, Kristine H.; Baillargeon, Renée

    2012-01-01

    For more than two decades, researchers have argued that young children do not understand mental states such as beliefs. Part of the evidence for this claim comes from preschoolers’ failure at verbal tasks that require the understanding that others may hold false beliefs. Here, we used a novel nonverbal task to examine 15-month-old infants’ ability to predict an actor’s behavior on the basis of her true or false belief about a toy’s hiding place. Results were positive, supporting the view that, from a young age, children appeal to mental states—goals, perceptions, and beliefs—to explain the behavior of others. PMID:15821091

  14. The Positive-Pion Double-Charge Reaction: Experiments on the Isotopic Pairs OXYGEN-16,18 and MAGNESIUM-24,26.

    NASA Astrophysics Data System (ADS)

    Greene, Steven Joseph

    1981-06-01

    The ((pi)('+),(pi)('-)) double-charge-exchange (DCX) reaction has been performed on targets of T = 0,1 isospin (and isotopic) pairs ('16,18)O and ('24,26)Mg. Energy excitation functions of d(sigma)/d(OMEGA), across the (3,3) (pi)-N resonance, are presented for transitions to double -isobaric analog state (DIAS) and non-DIAS ground-state residual nuclei. Angular distributions in the region of 5(DEGREES)-33(DEGREES) are presented for the DIAS from the T = 1 nuclei. The simularities and differences of DIAS and non-DIAS distributions are discussed in relation to reaction-mechanism and nuclear-structure effects. Also, a simple, two-amplitude model for the ('18)O excitation function, consistent with the data, is presented. The utility of DCX in nuclear mass measurements is discussed, with some examples.

  15. Positive-pion double-charge-exchange reaction: experiments on the isotopic pairs oxygen-16,18 and magnesium-24,26

    SciTech Connect

    Greene, S.J.

    1981-06-01

    The (..pi../sup +/,..pi../sup -/) double-charge-exchange (DCX) reaction has been performed on targets of T = 0,1 isospin (and isotopic) pairs /sup 16/ /sup 18/O and /sup 24/ /sup 26/Mg. Energy excitation functions of d sigma/d ..cap omega.., across the (3,3) ..pi..-N resonance, are presented for transitions to double-isobaric analog state (DIAS) and non-DIAS ground-state residual nuclei. Angular distributions in the region of 5/sup 0/ to 33/sup 0/ are presented for the DIAS from the T = 1 nuclei. The similarities and differences of DIAS and non-DIAS distributions are discussed in relation to reaction-mechanism and nuclear-structure effects. Also, a simple, two-amplitude model for the /sup 18/O excitation function, consistent with the data, is presented. The utility of DCX in nuclear mass measurements is discussed, with some examples.

  16. Remedies by competitors for false advertising.

    PubMed

    Hirsch, B D; Wilcox, D P

    1990-05-01

    Patients who are victimized as a consequence of false medical advertising are not the only ones who can sue for damages. Under section 43(a) of the Lanham Act, effective November 17, 1989, anyone "who believes that he or she is or is likely to be damaged" by deceptive advertising may bring a civil action for damages (1). Competing physicians may sue other physicians who falsely advertise that they possess unique skills and achieve better results than other physicians because they employ exclusive methods of treatment or claim that certain surgical procedures they perform in the office are absolutely safe and without risk or who advertise false professional credentials to lure patients. Voluntary informed consent excludes the use of deceit. Misrepresentation through advertising deprives a patient of the right to exercise an informed consent (2). A patient who relies on a doctor's false advertising in agreeing to a procedure that causes the patient injury may sue for malpractice even if the procedure was performed without negligence. False medical advertising also exposes the advertiser to litigation by competitors for unfair competition. This article is concerned with the remedy that may be available for instituting private litigation against physicians and other health care providers who engage in untruthful advertising. PMID:2343426

  17. False lock performance of quadriphase receivers

    NASA Technical Reports Server (NTRS)

    Simon, M. K.

    1979-01-01

    Quadriphase receivers, like biphase receivers, have the ability to false lock on a sideband on the data modulation. The theory associated with this phenomenon for receivers of binary phase-shift-keying (BPSK), using Costas loop demodulation, has recently been documented in the literature. This paper considers the corresponding theory for receivers of balanced quadriphase-shift-keying (QPSK) employing a quadriphase Costas loop (or equivalent fourth-power loop) for demodulation. Specific closed form expressions for false lock performance are developed and numerically evaluated for the particular case of single pole arm filters and an NRZ data format for each of the two statistically independent quadrature modulations.

  18. Pluto behaving badly: false beliefs and their consequences.

    PubMed

    Berkowitz, Shari R; Laney, Cara; Morris, Erin K; Garry, Maryanne; Loftus, Elizabeth F

    2008-01-01

    We exposed college students to suggestive materials in order to lead them to believe that, as children, they had a negative experience at Disneyland involving the Pluto character. A sizable minority of subjects developed a false belief or memory that Pluto had uncomfortably licked their ear. Suggestions about a positive experience with Pluto led to even greater acceptance of a lovable ear-licking episode. False beliefs and memories had repercussions; those seduced by the bad suggestions were not willing to pay as much for a Pluto souvenir. These findings are among the first to demonstrate that false beliefs can have repercussions for people, meaning that they can influence their later thoughts, beliefs, and behaviors.

  19. Left ventricular false tendons: anatomic, echocardiographic, and pathophysiologic insights.

    PubMed

    Silbiger, Jeffrey J

    2013-06-01

    Left ventricular (LV) false tendons are chordlike structures that traverse the LV cavity. They attach to the septum, to the papillary muscles, or to the free wall of the ventricle but not to the mitral valve. They are found in approximately half of human hearts examined at autopsy. Although it has been more than 100 years since their initial description, the functional significance of these structures remains largely unexplored. It has been suggested that they retard LV remodeling by tethering the walls to which they are attached, but there are few data to substantiate this. Some studies have suggested that false tendons reduce the severity of functional mitral regurgitation by stabilizing the position of the papillary muscles as the left ventricle enlarges. LV false tendons may also have deleterious effects and have been implicated in promoting membrane formation in discrete subaortic stenosis. This article reviews current understanding of the anatomy, echocardiographic characteristics, and pathophysiology of these structures.

  20. Synthesis of 4-substituted oxazolo[4,5-c]quinolines by direct reaction at the C-4 position of oxazoles.

    PubMed

    Akula, Mahesh; Thigulla, Yadagiri; Davis, Connor; Jha, Mukund; Bhattacharya, Anupam

    2015-03-01

    A facile synthesis of 4-aryl substituted oxazolo[4,5-c]quinolines has been described via a modified Pictet-Spengler method and using Cu(TFA)2 as a catalyst. The developed methodology directly functionalizes the C-4 position of oxazoles without the aid of any prefunctionalization, in the presence of the more reactive C-2 position in good yields. The versatility of the established method has been demonstrated by its application in the synthesis of 4-substituted oxazolo-[1,8]naphthyridine ring systems. PMID:25574832