Science.gov

Sample records for 2012-01-01 false position

  1. 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.

  2. 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.

  3. 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

  4. 14 CFR 23.1385 - Position light system installation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Position light system installation. 23.1385... Lights § 23.1385 Position light system installation. (a) General. Each part of each position light system... requirements of §§ 23.1387 through 23.1397. (b) Left and right position lights. Left and right position...

  5. 5 CFR 319.203 - Establishment of positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Establishment of positions. 319.203... SL and ST positions within an allocation, but the positions must be established in accordance with... procedures. (b) Before an SL or ST position may be established, an agency must: (1) Prepare a description...

  6. 5 CFR 319.102 - Senior-level positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Senior-level positions. 319.102 Section.... (a) SL positions are positions classified above GS-15 pursuant to 5 U.S.C. 5108 that are not covered by other pay systems (e.g. the SES and ST systems). (b) Positions in agencies that are excluded...

  7. 5 CFR 214.402 - Career reserved positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Career reserved positions. 214.402... EXECUTIVE SERVICE Types of Positions § 214.402 Career reserved positions. (a) The head of each agency is responsible for designating career reserved positions in accordance with the regulations in this section....

  8. 5 CFR 319.202 - Allocation of positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Allocation of positions. 319.202 Section 319.202 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS EMPLOYMENT... § 319.202 Allocation of positions. SL and ST positions may be established only under a...

  9. 5 CFR 319.402 - Scientific and professional positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... § 319.402 Scientific and professional positions. (a) ST positions are filled without competitive examination under 5 U.S.C. 3325. (b) ST positions are not subject to the citizenship requirements in 5 CFR... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Scientific and professional...

  10. 7 CFR 996.15 - Positive lot identification.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Positive lot identification. 996.15 Section 996.15... STANDARDS FOR DOMESTIC AND IMPORTED PEANUTS MARKETED IN THE UNITED STATES Definitions § 996.15 Positive lot identification. Positive lot identification is a means, approved by the Inspection Service, of relating...

  11. 14 CFR 137.47 - Operation without position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Operation without position lights. 137.47... AIRCRAFT OPERATIONS Operating Rules § 137.47 Operation without position lights. Notwithstanding part 91 of this chapter, an aircraft may be operated without position lights if prominent unlighted objects...

  12. 5 CFR 319.103 - Scientific and professional positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... REGULATIONS EMPLOYMENT IN SENIOR-LEVEL AND SCIENTIFIC AND PROFESSIONAL POSITIONS General § 319.103 Scientific and professional positions. (a) ST positions are established under 5 U.S.C. 3104 to carry out research... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Scientific and professional...

  13. 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.

  14. 14 CFR 31.65 - Position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Position lights. 31.65 Section 31.65 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS...; and z is not greater than 0.002. (2) Aviation white— x is not less than 0.300 and not greater than...

  15. 5 CFR 317.402 - Career reserved positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Career reserved positions. 317.402 Section 317.402 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS EMPLOYMENT IN THE SENIOR EXECUTIVE SERVICE Qualifications Standards § 317.402 Career reserved positions....

  16. 14 CFR 23.699 - Wing flap position indicator.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Wing flap position indicator. 23.699 Section 23.699 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... Construction Control Systems § 23.699 Wing flap position indicator. There must be a wing flap...

  17. 10 CFR 712.10 - Designation of HRP positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Designation of HRP positions. 712.10 Section 712.10 Energy DEPARTMENT OF ENERGY HUMAN RELIABILITY PROGRAM Establishment of and Procedures for the Human Reliability..., administrative, or other controls could be implemented that would prevent the position from being designated...

  18. 5 CFR 9701.231 - Conversion of positions and employees to the DHS classification system.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Conversion of positions and employees to... from the GS system, a prevailing rate system, the SL/ST system, or the SES system, as provided in... position to a band and for converting SL/ST and SES positions to a band upon initial implementation of...

  19. 14 CFR 101.39 - Balloon position reports.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 2 2012-01-01 2012-01-01 false Balloon position reports. 101.39 Section 101.39 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES MOORED BALLOONS, KITES, AMATEUR ROCKETS AND UNMANNED...

  20. 5 CFR 532.263 - Special wage schedules for production facilitating positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Special wage schedules for production facilitating positions. 532.263 Section 532.263 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL... schedules for production facilitating positions. (a) The lead agency in each FWS wage area shall...

  1. 14 CFR 23.523 - Design weights and center of gravity positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Design weights and center of gravity... Structure Water Loads § 23.523 Design weights and center of gravity positions. (a) Design weights. The water... water taxi and takeoff run) must be used. (b) Center of gravity positions. The critical centers...

  2. 14 CFR 25.523 - Design weights and center of gravity positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Design weights and center of gravity... Design weights and center of gravity positions. (a) Design weights. The water load requirements must be...) must be used. (b) Center of gravity positions. The critical centers of gravity within the limits...

  3. 5 CFR 330.404 - Displacement of preference eligibles occupying restricted positions in contracting out situations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Displacement of preference eligibles occupying restricted positions in contracting out situations. 330.404 Section 330.404 Administrative... (GENERAL) Positions Restricted to Preference Eligibles § 330.404 Displacement of preference...

  4. 5 CFR 1.1 - Positions and employees affected by the rules in this subchapter.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Positions and employees affected by the rules in this subchapter. 1.1 Section 1.1 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE RULES COVERAGE AND DEFINITIONS (RULE I) § 1.1 Positions and employees affected by the rules...

  5. 14 CFR 25.1395 - Maximum intensities in overlapping beams of forward and rear position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Maximum intensities in overlapping beams of forward and rear position lights. 25.1395 Section 25.1395 Aeronautics and Space FEDERAL AVIATION... Equipment Lights § 25.1395 Maximum intensities in overlapping beams of forward and rear position lights....

  6. 14 CFR 29.1395 - Maximum intensities in overlapping beams of forward and rear position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Maximum intensities in overlapping beams of forward and rear position lights. 29.1395 Section 29.1395 Aeronautics and Space FEDERAL AVIATION... Equipment Lights § 29.1395 Maximum intensities in overlapping beams of forward and rear position lights....

  7. 14 CFR 23.1395 - Maximum intensities in overlapping beams of position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Maximum intensities in overlapping beams of position lights. 23.1395 Section 23.1395 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... AIRPLANES Equipment Lights § 23.1395 Maximum intensities in overlapping beams of position lights....

  8. 14 CFR 27.1395 - Maximum intensities in overlapping beams of forward and rear position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Maximum intensities in overlapping beams of forward and rear position lights. 27.1395 Section 27.1395 Aeronautics and Space FEDERAL AVIATION... Equipment Lights § 27.1395 Maximum intensities in overlapping beams of forward and rear position lights....

  9. 14 CFR 29.1391 - Minimum intensities in the horizontal plane of forward and rear position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Minimum intensities in the horizontal plane of forward and rear position lights. 29.1391 Section 29.1391 Aeronautics and Space FEDERAL AVIATION... Equipment Lights § 29.1391 Minimum intensities in the horizontal plane of forward and rear position...

  10. 14 CFR 25.1391 - Minimum intensities in the horizontal plane of forward and rear position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Minimum intensities in the horizontal plane of forward and rear position lights. 25.1391 Section 25.1391 Aeronautics and Space FEDERAL AVIATION... Equipment Lights § 25.1391 Minimum intensities in the horizontal plane of forward and rear position...

  11. 14 CFR 27.1391 - Minimum intensities in the horizontal plane of forward and rear position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Minimum intensities in the horizontal plane of forward and rear position lights. 27.1391 Section 27.1391 Aeronautics and Space FEDERAL AVIATION... Equipment Lights § 27.1391 Minimum intensities in the horizontal plane of forward and rear position...

  12. 5 CFR 532.277 - Special wage schedules for U.S. Navy positions in Bridgeport, California.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Special wage schedules for U.S. Navy positions in Bridgeport, California. 532.277 Section 532.277 Administrative Personnel OFFICE OF PERSONNEL... wage schedules for U.S. Navy positions in Bridgeport, California. (a) The Department of Defense...

  13. 14 CFR 23.1391 - Minimum intensities in the horizontal plane of position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Minimum intensities in the horizontal plane of position lights. 23.1391 Section 23.1391 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... CATEGORY AIRPLANES Equipment Lights § 23.1391 Minimum intensities in the horizontal plane of...

  14. 5 CFR 532.271 - Special wage schedules for National Park Service positions in overlap areas.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Special wage schedules for National Park... wage schedules for National Park Service positions in overlap areas. (a)(1) The Department of the Interior shall establish special schedules for wage employees of the National Park Service whose...

  15. 5 CFR 213.3301 - Positions of a confidential or policy-determining nature.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Positions of a confidential or policy-determining nature. 213.3301 Section 213.3301 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL... or policy-determining nature. (a) Upon specific authorization by OPM, agencies may make...

  16. 12 CFR 611.326 - Floor nominations for open Farm Credit bank and association director positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 7 2012-01-01 2012-01-01 false Floor nominations for open Farm Credit bank and association director positions. 611.326 Section 611.326 Banks and Banking FARM CREDIT ADMINISTRATION FARM CREDIT SYSTEM ORGANIZATION Election of Directors and Other Voting Procedures § 611.326 Floor...

  17. 16 CFR Figure 7 to Part 1203 - Typical Test Apparatus for Positional Stability Test

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Typical Test Apparatus for Positional Stability Test 7 Figure 7 to Part 1203 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION CONSUMER PRODUCT SAFETY ACT REGULATIONS SAFETY STANDARD FOR BICYCLE HELMETS Pt. 1203, Fig. 7 Figure 7 to Part...

  18. 5 CFR 731.106 - Designation of public trust positions and investigative requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Designation of public trust positions and investigative requirements. 731.106 Section 731.106 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT (CONTINUED) CIVIL SERVICE REGULATIONS (CONTINUED) SUITABILITY Scope § 731.106 Designation of public...

  19. 10 CFR 26.103 - Determining a confirmed positive test result for alcohol.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Determining a confirmed positive test result for alcohol. 26.103 Section 26.103 Energy NUCLEAR REGULATORY COMMISSION FITNESS FOR DUTY PROGRAMS Collecting... fitness indicates that the donor is fit to safely and competently perform his or her duties....

  20. 5 CFR 894.303 - What happens to my enrollment if I transfer to an excluded position?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false What happens to my enrollment if I transfer to an excluded position? 894.303 Section 894.303 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT (CONTINUED) CIVIL SERVICE REGULATIONS (CONTINUED) FEDERAL EMPLOYEES DENTAL AND VISION...

  1. 5 CFR 532.253 - Special rates or rate ranges for leader, supervisory, and production facilitating positions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Special rates or rate ranges for leader, supervisory, and production facilitating positions. 532.253 Section 532.253 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PREVAILING RATE SYSTEMS Prevailing Rate Determinations § 532.253 Special rates or...

  2. 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.

  3. 14 CFR 23.1393 - Minimum intensities in any vertical plane of position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Minimum intensities in any vertical plane... CATEGORY AIRPLANES Equipment Lights § 23.1393 Minimum intensities in any vertical plane of position lights... above or below the horizontal plane Intensity, l 0° 1.00 0° to 5° 0.90 5° to 10° 0.80 10° to 15° 0.70...

  4. 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.

  5. 14 CFR 29.1393 - Minimum intensities in any vertical plane of forward and rear position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Minimum intensities in any vertical plane... Equipment Lights § 29.1393 Minimum intensities in any vertical plane of forward and rear position lights... above or below the horizontal plane Intensity, I 0° 1.00 0° to 5° .90 5° to 10° .80 10° to 15° .70...

  6. 14 CFR 27.1393 - Minimum intensities in any vertical plane of forward and rear position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Minimum intensities in any vertical plane... Equipment Lights § 27.1393 Minimum intensities in any vertical plane of forward and rear position lights... above or below the horizontal plane Intensity, l 0° 1.00 0° to 5° 0.90 5° to 10° 0.80 10° to 15° 0.70...

  7. 14 CFR 25.1393 - Minimum intensities in any vertical plane of forward and rear position lights.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Minimum intensities in any vertical plane... Equipment Lights § 25.1393 Minimum intensities in any vertical plane of forward and rear position lights... above or below the horizontal plane Intensity, l 0° 1.00 0° to 5° 0.90 5° to 10° 0.80 10° to 15° 0.70...

  8. 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...

  9. 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…

  10. 7 CFR 1450.12 - Filing of false claims.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Filing of false claims. 1450.12 Section 1450.12 Agriculture Regulations of the Department of Agriculture (Continued) COMMODITY CREDIT CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS BIOMASS CROP ASSISTANCE PROGRAM (BCAP)...

  11. 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

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 16 CFR 301.34 - Misbranded or falsely invoiced fur products.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 1 2012-01-01 2012-01-01 false Misbranded or falsely invoiced fur products... CONGRESS RULES AND REGULATIONS UNDER FUR PRODUCTS LABELING ACT Regulations § 301.34 Misbranded or falsely invoiced fur products. (a) If a person subject to section 3 of the Act with respect to a fur product...

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 13 CFR 108.507 - Violations based on false filings and nonperformance of agreements with SBA.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Violations based on false filings and nonperformance of agreements with SBA. 108.507 Section 108.507 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION NEW MARKETS VENTURE CAPITAL (âNMVCâ) PROGRAM Managing the Operations of...

  2. 13 CFR 107.507 - Violations based on false filings and nonperformance of agreements with SBA.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Violations based on false filings and nonperformance of agreements with SBA. 107.507 Section 107.507 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION SMALL BUSINESS INVESTMENT COMPANIES Managing the Operations of a...

  3. 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…

  4. 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…

  5. 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…

  6. 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.

  7. 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.

  8. 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.

  9. ``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.

  10. 15 CFR 30.71 - False or fraudulent reporting on or misuse of the Automated Export System.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 15 Commerce and Foreign Trade 1 2012-01-01 2012-01-01 false False or fraudulent reporting on or misuse of the Automated Export System. 30.71 Section 30.71 Commerce and Foreign Trade Regulations... REGULATIONS Penalties § 30.71 False or fraudulent reporting on or misuse of the Automated Export System....

  11. 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

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. "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…

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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

  5. 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

  6. "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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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...

  16. 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…

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. 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…

  3. 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…

  4. 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.

  5. 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...

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. "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

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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

  15. [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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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%.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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).

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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%.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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…

  4. 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

  5. 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.

  6. 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.

  7. [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.

  8. [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.

  9. 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.

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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

  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. 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

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 5 CFR 319.301 - Qualifications standards.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Qualifications standards. 319.301 Section 319.301 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS EMPLOYMENT... are required in the ST position....

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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).

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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)

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.…

  3. 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

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. 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).

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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

  18. 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

  19. 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.

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 5 CFR 842.804 - Evidence.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Evidence. 842.804 Section 842.804... Controllers § 842.804 Evidence. (a) An agency head's determination under § 842.803(a) (finding that a position...) must be based on the official position description and any other evidence deemed appropriate by...

  16. 14 CFR 437.67 - Tracking a reusable suborbital rocket.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Tracking a reusable suborbital rocket. 437... a reusable suborbital rocket. A permittee must— (a) During permitted flight, measure in real time the position and velocity of its reusable suborbital rocket; and (b) Provide position and...

  17. 14 CFR 25.699 - Lift and drag device indicator.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Lift and drag device indicator. 25.699....699 Lift and drag device indicator. (a) There must be means to indicate to the pilots the position of each lift or drag device having a separate control in the cockpit to adjust its position. In...

  18. 5 CFR 9701.202 - Coverage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... senior-level (SL) and scientific or professional (ST) positions who would otherwise be covered by 5 U.S.C... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Coverage. 9701.202 Section 9701.202... classification system established under 5 U.S.C. chapter 51; (2) Employees and positions that would otherwise...

  19. 5 CFR 319.104 - Applicable instructions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Applicable instructions. 319.104 Section 319.104 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS EMPLOYMENT... service positions and employment apply to positions and employment under the SL and ST systems...

  20. 5 CFR 319.201 - Coverage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... applies to SL positions in an executive agency per 5 U.S.C. 5108 and ST positions in any agency per 5 U.S... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Coverage. 319.201 Section 319.201 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS EMPLOYMENT IN SENIOR-LEVEL...

  1. 5 CFR 315.908 - Appeals.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Appeals. 315.908 Section 315.908... EMPLOYMENT Probation on Initial Appointment to a Supervisory or Managerial Position § 315.908 Appeals. (a) An... nonsupervisory position, has no appeal right. (b) An employee who alleges that an agency action under...

  2. 14 CFR 25.1021 - Oil system drains.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Oil system drains. 25.1021 Section 25.1021 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS...; and (b) Have manual or automatic means for positive locking in the closed position....

  3. 14 CFR 27.1021 - Oil system drains.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Oil system drains. 27.1021 Section 27.1021 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS...) Have manual or automatic means for positive locking in the closed position....

  4. 14 CFR 29.1021 - Oil system drains.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Oil system drains. 29.1021 Section 29.1021 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS...; and (b) Have manual or automatic means for positive locking in the closed position....

  5. 14 CFR 125.139 - Oil system drains.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Oil system drains. 125.139 Section 125.139....139 Oil system drains. Accessible drains incorporating either a manual or automatic means for positive locking in the closed position must be provided to allow safe drainage of the entire oil system....

  6. 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

  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. 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.

  9. 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.

  10. 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.

  11. 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

  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. PMID:27621807

  13. 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).

  14. 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.

  15. 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

  16. 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.

  17. 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

  18. 5 CFR 842.908 - Mandatory separation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Mandatory separation. 842.908 Section 842... separation. (a) Effective on and after October 17, 1999, the mandatory separation provisions of 5 U.S.C. 8425 apply to all nuclear materials couriers including those in secondary positions. A mandatory...

  19. 9 CFR 55.3 - Appraisal and destruction of captive cervids.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false Appraisal and destruction of captive cervids. 55.3 Section 55.3 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE... of captive cervids. (a) CWD positive herds, or individual CWD suspect animals or exposed...

  20. 5 CFR 842.905 - Evidence.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Evidence. 842.905 Section 842.905... EMPLOYEES RETIREMENT SYSTEM-BASIC ANNUITY Nuclear Materials Couriers § 842.905 Evidence. (a) The Secretary... official position description and any other evidence deemed appropriate by the agency head for making...

  1. 5 CFR 831.905 - Evidence.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Evidence. 831.905 Section 831.905...) RETIREMENT Law Enforcement Officers and Firefighters § 831.905 Evidence. (a) An agency head's determination... determination under § 831.904 must be based on the official position description and any other evidence...

  2. 5 CFR 842.1004 - Evidence.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Evidence. 842.1004 Section 842.1004... EMPLOYEES RETIREMENT SYSTEM-BASIC ANNUITY Customs and Border Protection Officers § 842.1004 Evidence. (a... the official position description and any other evidence deemed appropriate by the agency head...

  3. 10 CFR 850.35 - Medical removal.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Medical removal. 850.35 Section 850.35 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements § 850.35 Medical... or more positive Be-LPT results, chronic beryllium disease diagnosis, an examining...

  4. 14 CFR 415.131 - Flight safety system crew data.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Flight safety system crew data. 415.131... Launch Vehicle From a Non-Federal Launch Site § 415.131 Flight safety system crew data. (a) An applicant's safety review document must identify each flight safety system crew position and the role of...

  5. 13 CFR 120.1708 - Pool Certificates.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Pool Certificates. 120.1708... of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1708 Pool Certificates. (a) SBA Guarantee of Pool Certificates. SBA guarantees to a Pool Investor the timely payment...

  6. 13 CFR 120.1713 - Seller's Pool Loan origination.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Seller's Pool Loan origination... Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1713 Seller's Pool Loan origination. SBA is entitled to recover from the Seller losses incurred by SBA on...

  7. 13 CFR 120.1709 - Transfers of Pool Certificates.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Transfers of Pool Certificates... Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1709 Transfers of Pool Certificates. (a) Transfer of Pool Certificates. A Pool Certificate is transferable....

  8. 13 CFR 120.1715 - Seller's Pool Loan liquidation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Seller's Pool Loan liquidation... Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1715 Seller's Pool Loan liquidation. Subject to § 120.1718 of this subpart J, the Seller must liquidate...

  9. 13 CFR 120.1714 - Seller's Pool Loan servicing.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Seller's Pool Loan servicing. 120... Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1714 Seller's Pool Loan servicing. Subject to § 120.1718 of this subpart J, the Seller must service...

  10. 13 CFR 120.1723 - Pool Loan receivables received by Seller.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Pool Loan receivables received by... LOANS Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1723 Pool Loan receivables received by Seller. Any Pool Loan Receivables received by Seller...

  11. 13 CFR 120.1705 - Pool formation requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Pool formation requirements. 120... Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1705 Pool formation requirements. (a) Initiation of Pool formation. Only an entity approved by SBA to be a...

  12. 13 CFR 120.1717 - Seller's Pool Loan deferments.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Seller's Pool Loan deferments. 120... Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1717 Seller's Pool Loan deferments. Without the prior written consent of SBA, Seller, at the request of...

  13. 13 CFR 120.1726 - Pool Certificates a Seller cannot purchase.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Pool Certificates a Seller cannot... LOANS Establishment of SBA Secondary Market Guarantee Program for First Lien Position 504 Loan Pools § 120.1726 Pool Certificates a Seller cannot purchase. Neither a Seller, nor any of its...

  14. 16 CFR 1203.14 - Peripheral vision test.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Peripheral vision test. 1203.14 Section 1203... SAFETY STANDARD FOR BICYCLE HELMETS The Standard § 1203.14 Peripheral vision test. Position the helmet on... the helmet to set the comfort or fit padding. (Note: Peripheral vision clearance may be...

  15. 5 CFR 352.502 - Coverage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Coverage. 352.502 Section 352.502 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS REEMPLOYMENT RIGHTS....502 Coverage. This subpart applies to any of the following serving in a position in the...

  16. 5 CFR 534.601 - Coverage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Coverage. 534.601 Section 534.601 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PAY UNDER OTHER SYSTEMS Pay for Administrative Appeals Judge Positions § 534.601 Coverage. (a) This subpart implements 5 U.S.C. 5372b and...

  17. 5 CFR 930.103 - Coverage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Coverage. 930.103 Section 930.103 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT (CONTINUED) CIVIL SERVICE REGULATIONS (CONTINUED) PROGRAMS FOR SPECIFIC POSITIONS AND EXAMINATIONS (MISCELLANEOUS) Motor Vehicle Operators § 930.103...

  18. 5 CFR 511.605 - Time limits.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Time limits. 511.605 Section 511.605... GENERAL SCHEDULE Classification Appeals § 511.605 Time limits. (a) Employees. (1) An employee may submit an appeal of his or her official position at any time. If the employee has suffered a loss in...

  19. 14 CFR Appendix B to Part 1215 - Factors Affecting Standard Charges

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Factors Affecting Standard Charges B Appendix B to Part 1215 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION TRACKING AND... standard services set forth in appendix A. Flexible Time or position constrained Emergency...

  20. 5 CFR 9701.211 - Occupational clusters.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Occupational clusters. 9701.211 Section... RESOURCES MANAGEMENT SYSTEM Classification Classification Structure § 9701.211 Occupational clusters. For the purpose of classifying positions, DHS may, after coordination with OPM, establish...

  1. 16 CFR 1507.4 - Bases.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Bases. 1507.4 Section 1507.4 Commercial... § 1507.4 Bases. The base or bottom of fireworks devices that are operated in a standing upright position shall have the minimum horizontal dimensions or the diameter of the base equal to at least one-third...

  2. 14 CFR 1216.103 - Responsibilities of NASA officials.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Responsibilities of NASA officials. 1216... QUALITY Policy on Environmental Quality and Control § 1216.103 Responsibilities of NASA officials. (a) The... NASA policies and positions on matters pertaining to environmental protection and enhancement;...

  3. 14 CFR 27.675 - Stops.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Stops. 27.675 Section 27.675 Aeronautics... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Control Systems § 27.675 Stops. (a) Each control system must have stops that positively limit the range of motion of the pilot's controls. (b)...

  4. 14 CFR 29.675 - Stops.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Stops. 29.675 Section 29.675 Aeronautics... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Control Systems § 29.675 Stops. (a) Each control system must have stops that positively limit the range of motionof the pilot's controls. (b)...

  5. 12 CFR 201.104 - Eligibility of consumer loans and finance company paper.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 2 2012-01-01 2012-01-01 false Eligibility of consumer loans and finance....104 Eligibility of consumer loans and finance company paper. (a) The Board of Governors has clarified and modified its position with respect to the eligibility of consumer loans and finance company...

  6. 14 CFR 125.267 - Flight navigator and long-range navigation equipment.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Flight navigator and long-range navigation... Requirements § 125.267 Flight navigator and long-range navigation equipment. (a) No certificate holder may...-range means of navigation which enable a reliable determination to be made of the position of...

  7. 5 CFR 330.1001 - Withdrawal from competition.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Withdrawal from competition. 330.1001... RECRUITMENT, SELECTION, AND PLACEMENT (GENERAL) Prohibited Practices § 330.1001 Withdrawal from competition... applicant or eligible to withdraw from competition or eligibility, for a position in the competitive...

  8. 5 CFR 319.105 - Reporting requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Reporting requirements. 319.105 Section 319.105 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS EMPLOYMENT.... Agencies shall report such information as may be requested by OPM relating to SL and ST positions...

  9. 5 CFR 630.301 - Annual leave accrual and accumulation-Senior Executive Service, Senior-Level, and Scientific and...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... system established under 5 U.S.C. chapter 43 and 5 CFR part 430, subparts B and C, or other applicable... subject to 5 U.S.C. 5383; or (2) Holds a senior-level (SL) or scientific or professional (ST) position... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Annual leave accrual and...

  10. 5 CFR 319.302 - Individual qualifications.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Individual qualifications. 319.302 Section 319.302 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS... appointed to SL and ST positions. The agency head must determine that the individual meets...

  11. 5 CFR 430.402 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... means the policies, practices, and procedures an agency establishes under 5 U.S.C. chapter 43 and 5 CFR... professional position (ST) paid under 5 U.S.C. 5376. ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Definitions. 430.402 Section...

  12. 5 CFR 9701.302 - Coverage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... senior-level (SL) and scientific or professional (ST) positions who would otherwise be covered by 5 U.S.C... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Coverage. 9701.302 Section 9701.302... system established under 5 U.S.C. chapter 53, subchapter III; (2) Employees who would otherwise...

  13. 14 CFR 25.533 - Hull and main float bottom pressures.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Hull and main float bottom pressures. 25.533 Section 25.533 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... flaps extended in the appropriate takeoff position; and βk=angle of dead rise at keel, in...

  14. 14 CFR 23.671 - General.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false General. 23.671 Section 23.671 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Systems § 23.671 General. (a) Each control must operate easily, smoothly, and positively enough to...

  15. 9 CFR 381.87 - Tumors.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 2 2012-01-01 2012-01-01 false Tumors. 381.87 Section 381.87 Animals and Animal Products FOOD SAFETY AND INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE AGENCY ORGANIZATION... by the size, position, or nature of the tumor, the whole carcass shall be condemned....

  16. 5 CFR 2635.705 - Use of official time.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... the correspondence at home on her own time. Where the compensation is not adequate, however, the... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Use of official time. 2635.705 Section... CONDUCT FOR EMPLOYEES OF THE EXECUTIVE BRANCH Misuse of Position § 2635.705 Use of official time. (a)...

  17. 14 CFR 25.1531 - Maneuvering flight load factors.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Maneuvering flight load factors. 25.1531 Section 25.1531 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION... positive limit load factors determined from the maneuvering diagram in § 25.333(b), must be established....

  18. 14 CFR 1206.102 - General policy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false General policy. 1206.102 Section 1206.102 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION AVAILABILITY OF AGENCY RECORDS TO MEMBERS....C. 552), a positive and continuing obligation exists for NASA to make available to the...

  19. 9 CFR 80.2 - General restrictions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false General restrictions. 80.2 Section 80.2 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE... ANIMALS § 80.2 General restrictions. Domestic animals that are positive to an official Johne's...

  20. 5 CFR 315.902 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Definitions. 315.902 Section 315.902 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS CAREER AND CAREER-CONDITIONAL EMPLOYMENT Probation on Initial Appointment to a Supervisory or Managerial Position § 315.902 Definitions....

  1. 5 CFR 315.903 - Coverage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Coverage. 315.903 Section 315.903 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS CAREER AND CAREER-CONDITIONAL EMPLOYMENT Probation on Initial Appointment to a Supervisory or Managerial Position § 315.903 Coverage....

  2. 5 CFR 534.505 - Pay related matters.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Pay related matters. 534.505 Section 534.505 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PAY UNDER OTHER SYSTEMS Pay for Senior-Level and Scientific and Professional Positions § 534.505 Pay related matters....

  3. 5 CFR 532.315 - Additional survey jobs.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Additional survey jobs. 532.315 Section... RATE SYSTEMS Determining Rates for Principal Types of Positions § 532.315 Additional survey jobs. (a... add to the required survey jobs the specialized survey jobs listed below opposite the industry...

  4. 13 CFR 113.520 - Job classification and structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Job classification and structure... Prohibited § 113.520 Job classification and structure. A recipient shall not: (a) Classify a job as being for..., seniority systems, career ladders, or tenure systems for similar jobs, position descriptions, or...

  5. 5 CFR 2638.202 - Responsibilities of agency head.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Responsibilities of agency head. 2638.202... § 2638.202 Responsibilities of agency head. (a) In general. The head of each agency is responsible for... program in a positive and effective manner. (b) Selection of a designated agency ethics official. The...

  6. 12 CFR 268.201 - Age Discrimination in Employment Act.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 4 2012-01-01 2012-01-01 false Age Discrimination in Employment Act. 268.201... Complaints § 268.201 Age Discrimination in Employment Act. (a) As an alternative to filing a complaint under... ADEA if the Commission establishes a maximum age requirement for the position on the basis of...

  7. 5 CFR 2635.703 - Use of nonpublic information.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 3 2012-01-01 2012-01-01 false Use of nonpublic information. 2635.703 Section 2635.703 Administrative Personnel OFFICE OF GOVERNMENT ETHICS GOVERNMENT ETHICS STANDARDS OF ETHICAL CONDUCT FOR EMPLOYEES OF THE EXECUTIVE BRANCH Misuse of Position § 2635.703 Use of nonpublic information. (a) Prohibition. An employee...

  8. 12 CFR 250.141 - Member bank purchase of stock of “operations subsidiaries.”

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 4 2012-01-01 2012-01-01 false Member bank purchase of stock of âoperations... Member bank purchase of stock of “operations subsidiaries.” (a) The Board of Governors has reexamined its position that the so-called “stock-purchase prohibition” of section 5136 of the Revised Statutes (12...

  9. 5 CFR 4.1 - Prohibition against political activity.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Prohibition against political activity. 4... PRACTICES (RULE IV) § 4.1 Prohibition against political activity. No person employed in the executive branch... occupying a position in the competitive service shall take any active part in political management or...

  10. 5 CFR 316.701 - Public or private enterprise taken over by Government.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Public or private enterprise taken over... Competitive Service § 316.701 Public or private enterprise taken over by Government. (a) When the Office, or... a public or private enterprise, or an identifiable unit thereof, and that a position has...

  11. 5 CFR 732.201 - Sensitivity level designations and investigative requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 2 2012-01-01 2012-01-01 false Sensitivity level designations and... Requirements § 732.201 Sensitivity level designations and investigative requirements. (a) For purposes of this... material adverse effect on the national security as a sensitive position at one of three sensitivity...

  12. 14 CFR 25.1397 - Color specifications.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Color specifications. 25.1397 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment Lights § 25.1397 Color specifications. Each position light color must have the applicable International Commission on Illumination...

  13. 14 CFR 27.1397 - Color specifications.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Color specifications. 27.1397 Section 27... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Lights § 27.1397 Color specifications. Each position light color must have the applicable International Commission on Illumination...

  14. 14 CFR 29.1397 - Color specifications.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Color specifications. 29.1397 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Equipment Lights § 29.1397 Color specifications. Each position light color must have the applicable International Commission on Illumination...

  15. 14 CFR 23.1397 - Color specifications.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Color specifications. 23.1397 Section 23.1397 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... Color specifications. Each position light color must have the applicable International Commission...

  16. 10 CFR 707.8 - Applicant drug testing.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Applicant drug testing. 707.8 Section 707.8 Energy DEPARTMENT OF ENERGY WORKPLACE SUBSTANCE ABUSE PROGRAMS AT DOE SITES Procedures § 707.8 Applicant drug testing. An applicant for a testing designated position will be tested for the use of illegal drugs...

  17. 5 CFR 213.3199 - Temporary organizations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Temporary organizations. 213.3199 Section... SERVICE Excepted Schedules Schedule A § 213.3199 Temporary organizations. Positions on the staffs of temporary organizations, as defined in 5 U.S.C. 3161(a). Appointments may not exceed 3 years, but...

  18. 14 CFR 121.241 - Oil system drains.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Oil system drains. 121.241 Section 121.241..., FLAG, AND SUPPLEMENTAL OPERATIONS Special Airworthiness Requirements § 121.241 Oil system drains... position, must be provided to allow safe drainage of the entire oil system....

  19. 14 CFR 125.137 - Oil valves.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Oil valves. 125.137 Section 125.137....137 Oil valves. (a) Each oil valve must— (1) Comply with § 125.155; (2) Have positive stops or... the valve. (b) The closing of an oil shutoff means must not prevent feathering the propeller,...

  20. 14 CFR 25.871 - Leveling means.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Leveling means. 25.871 Section 25.871... STANDARDS: TRANSPORT CATEGORY AIRPLANES Design and Construction Miscellaneous § 25.871 Leveling means. There must be means for determining when the airplane is in a level position on the ground....

  1. 5 CFR 532.305 - Dominant industry.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Dominant industry. 532.305 Section 532... SYSTEMS Determining Rates for Principal Types of Positions § 532.305 Dominant industry. (a)(1) A specialized industry is a “dominant industry” if the number of wage employees in the wage area who are...

  2. 5 CFR 532.311 - Survey of specialized private industry related to a dominant industry.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Survey of specialized private industry related to a dominant industry. 532.311 Section 532.311 Administrative Personnel OFFICE OF PERSONNEL... Positions § 532.311 Survey of specialized private industry related to a dominant industry. If it...

  3. 5 CFR 532.303 - Specialized industry.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Specialized industry. 532.303 Section 532... SYSTEMS Determining Rates for Principal Types of Positions § 532.303 Specialized industry. (a)(1) Under the appropriated fund wage system, a “specialized industry” is a Federal activity engaged in...

  4. 14 CFR 29.755 - Hull buoyancy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Hull buoyancy. 29.755 Section 29.755... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Floats and Hulls § 29.755 Hull buoyancy... buoyancy of the hull and auxiliary floats, and wheel tires if used, provides a margin of positive...

  5. 5 CFR 575.203 - Eligible categories of employees.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Executive Service position paid under 5 U.S.C. 5383 or a Federal Bureau of Investigation and Drug... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Eligible categories of employees. 575.203 Section 575.203 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE...

  6. 5 CFR 575.103 - Eligible categories of employees.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ....S.C. 5376; (3) A Senior Executive Service position paid under 5 U.S.C. 5383 or a Federal Bureau of... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Eligible categories of employees. 575.103 Section 575.103 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE...

  7. 5 CFR 575.303 - Eligible categories of employees.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... position paid under 5 U.S.C. 5383 or a Federal Bureau of Investigation and Drug Enforcement Administration... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Eligible categories of employees. 575.303 Section 575.303 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE...

  8. 14 CFR 125.133 - Fuel valves.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Fuel valves. 125.133 Section 125.133 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR CARRIERS....133 Fuel valves. Each fuel valve must— (a) Comply with § 125.155; (b) Have positive stops or...

  9. 14 CFR 27.995 - Fuel valves.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Fuel valves. 27.995 Section 27.995... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Fuel System Components § 27.995 Fuel valves. (a) There must be a positive, quick-acting valve to shut off fuel to each engine individually. (b) The control...

  10. 14 CFR 298.30 - Public disclosure of policy on consumer protection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Public disclosure of policy on consumer... Limitations and Conditions on Exemptions and Operations § 298.30 Public disclosure of policy on consumer... conspicuous public place at each desk, station and position in the United States that is in charge of a...

  11. 12 CFR 611.220 - Outside directors.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 7 2012-01-01 2012-01-01 false Outside directors. 611.220 Section 611.220... of Directors § 611.220 Outside directors. (a) Eligibility, number and term. (1) Eligibility. No candidate for an outside director position may be a director, officer, employee, agent, or stockholder of...

  12. 7 CFR 1942.114 - Security.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 13 2012-01-01 2012-01-01 false Security. 1942.114 Section 1942.114 Agriculture... Security. Specific requirements for security for each loan will be included in the letter of conditions. Loans must be secured by the best security position practicable, in a manner which will...

  13. 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

  14. 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

  15. 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.

  16. 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

  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. 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.

  1. 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

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. 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.

  18. 9 CFR 91.8 - Sheep.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...-positive animal or an exposed animal, as defined in 9 CFR parts 54 and 79, or if it has ever been in an infected flock, source flock, or trace flock, as defined in 9 CFR parts 54 and 79; or if it is the progeny... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false Sheep. 91.8 Section 91.8 Animals...

  19. 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

  20. 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.

  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. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 14 CFR 415.15 - Rights not conferred by launch license.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... facilities, airspace, or outer space. ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Rights not conferred by launch license. 415.15 Section 415.15 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL...

  14. 7 CFR 65.120 - Chicken.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 CFR 381.170(a)(1). ... 7 Agriculture 3 2012-01-01 2012-01-01 false Chicken. 65.120 Section 65.120 Agriculture Regulations..., PORK, LAMB, CHICKEN, GOAT MEAT, PERISHABLE AGRICULTURAL COMMODITIES, MACADAMIA NUTS, PECANS,...

  15. 41 CFR 102-78.15 - What are historic properties?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... specifically defined at 36 CFR 800.16. ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false What are historic... Regulations System (Continued) FEDERAL MANAGEMENT REGULATION REAL PROPERTY 78-HISTORIC PRESERVATION...

  16. 41 CFR 109-26.501 - Purchase of new motor vehicles.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false Purchase of new motor vehicles. 109-26.501 Section 109-26.501 Public Contracts and Property Management Federal Property... motor vehicles....

  17. 5 CFR 412.201 - Management succession.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... pursuant to 5 CFR 410.202. ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Management succession. 412.201 Section 412.201 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS...

  18. 14 CFR 1250.103 - Discrimination prohibited.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Discrimination prohibited. 1250.103 Section 1250.103 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION NONDISCRIMINATION IN... Discrimination prohibited....

  19. 6 CFR 7.30 - Classification challenges.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 6 CFR 7.31. ... 6 Domestic Security 1 2012-01-01 2012-01-01 false Classification challenges. 7.30 Section 7.30... INFORMATION Classified Information § 7.30 Classification challenges. (a) Authorized holders of...

  20. 10 CFR Appendix C to Part 2 - [Reserved

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false C Appendix C to Part 2 Energy NUCLEAR REGULATORY COMMISSION RULES OF PRACTICE FOR DOMESTIC LICENSING PROCEEDINGS AND ISSUANCE OF ORDERS Appendix C to Part 2...