False Positive

Background Real world cardiology is faced with a low diagnostic yield of coronary angiography (CXA) in patients presenting with ACC/AHA class II CXA indication. Our aim was to analyze the clinical implication of a Cardiac MR (CMR) protocol including adenosine stress perfusion in this patient population. We examined whether CMR could enhance appropriate CXA indication and thus reduce the rate of pure diagnostic CXA. In addition, we compared the relative impact of CMR exam components (perfusion, function and viability assessment) in achieving this target. Methods 176 patients were referred for CXA with class II indication. 171 underwent complete additional CMR exam in a 1.5-T whole body CMR-scanner for myocardial function, ischemia and viability prior to CXA. The routine protocol for assessment of CAD consisted of functional imaging (long and short axes), adenosine stress- and rest-perfusion in short axis orientation and “late enhancement” imaging in long and short axes. Images were analyzed by two independent and blinded investigators. Interobserver differences were resolved by a third reader. Results There was a high association between CMR results and subsequent invasive findings (chi square for CMR perfusion deficit and stenosis >70% in CXA: 113.7, p70%. Four (2.3%) patients had false negative CMR findings. In 58 patients (33.9%) no relevant coronary artery stenosis could be observed, correctly predicted by CMR in 48 cases; in 10 (5.8%) patients CMR provided false positive results. Sensitivity of CMR to detect relevant CAD (>70% luminal narrowing) was 0.96, specificity 0.83, positive predictive value 0.92 and negative predictive value 0.92. Of the CMR components, perfusion deficit was the strongest independent predictor (odds ratio 132.3, p Conclusion In a great number of patients being referred to cath lab with ACC/AHA class II indication for CXA, CMR provides a high accuracy for decision making regarding appropriateness of the invasive exam. CMR prior to CXA could substantially reduce pure diagnostic coronary angiographies in patients with intermediate probability for CAD, in our patient-cohort from approximately 34% to 6%. Further studies are warranted to identify rare false negative CMR results.

Mixture modeling within the context of pharmacokinetic (PK)/pharmacodynamic (PD) mixed effects modeling is a useful tool to explore a population for the presence of two or more subpopulations, not explained by evaluated covariates. At present, statistical tests for the existence of mixed populations have not been developed. Therefore, a simulation study was undertaken to evaluate mixture modeling with NONMEM and explore the following questions. First, what is the probability of concluding that a mixed population exists when there truly is not a mixture (false positive significance level)? Second, what is the probability of concluding that a mixed population (two subpopulations) exists when there is truly a mixed population (power), and how well can the mixture be estimated, both in terms of the population parameters and the individual subject classification. Seizure count data were simulated using a Poisson distribution such that each subject's count could decrease from its baseline value, as a function of dose via an Emax model. The dosing design for the simulation was based on a trial with the investigational anti-epileptic drug pregabalin. Four hundred and forty seven subjects received pregabalin as add on therapy for partial seizures, each with a baseline seizure count and up to three subsequent seizure counts. For the mixtures, the two subpopulations were simulated to differ in their Emax values and relative proportions. One subpopulation always had its Emax set to unity (Emax hi), allowing the count to approach zero with increasing dose. The other subpopulation was allowed to vary in its Emax value (Emax lo=0.75, 0.5, 0.25, and 0) and in its relative proportion (pr) of the population (pr=0.05, 0.10, 0.25, and 0.50) giving a total of 4 ⋅ 4=16 different mixtures explored. Three hundred data sets were simulated for each scenario and estimations performed using NONMEM. Metrics used information about the parameter estimates, their standard errors (SE), the difference between minimum objective function (MOF) values for mixture and non-mixture models (MOF(δ)), the proportion of subjects classified correctly, and the estimated conditional probabilities of a subject being simulated as having Emax lo (Emax hi) given that they were estimated as having Emaxlo (Emax hi) and being estimated as having Emaxlo (Emax hi) given that they were simulated as having Emax lo (Emax hi). The false positive significance level was approximately 0.04 (using all 300 runs) or 0.078 (using only those runs with a successful covariance step), when there was no mixture. When simulating mixed data and for those characterizations with successful estimation and covariance steps, the median (range) percentage of 95% confidence intervals containing the true values for the parameters defining the mixture were 94% (89–96%), 89.5% (58–96%), and 95% (92–97%) for pr, Emax lo, and Emax hi, respectively. The median value of the estimated parameters pr, Emax lo (excluding the case when Emax lo was simulated to equal 0) and Emax hi within a scenario were within ±28% of the true values. The median proportion of subjects classified correctly ranged from 0.59 to 0.96. In conclusion, when no mixture was present the false positive probability was less than 0.078 and when mixtures were present they were characterized with varying degrees of success, depending on the nature of the mixture. When the difference between subpopulations was greater (as Emax lo approached zero or pr approached 0.5) the mixtures became easier to characterize.

The purpose of this study was to (a) examine the concurrent validity of the Dynamic Indicators of Basic Early Literacy Skills (DIBELS) with the Com- prehensive Test of Phonological Processing (CTOPP), and (b) explore the diag- nostic accuracy of the DIBELS in predicting CTOPP performance using suggested and alternative cut-scores. Eighty-six students were administered the DIBELS and the CTOPP in

A method is presented for the detection of Listeria monocytogenes in food, which produces definitive results on the third day after the sample collection. The method is equivalent to EN ISO 11290-1 or ISO 10560 in terms of the same detection limit of 100 cfu per 25 or 10 g and 100% relative accuracy. The version alternative to EN ISO 11290-1 begins with a primary enrichment in half Fraser broth (24 h), secondary enrichment in Fraser broth (24 h) and post-enrichment in brain heart infusion broth (5 h). The version alternative to ISO 10560 begins with enrichment in Listeria enrichment broth (48 h) and post-enrichment in tryptone soya broth (5 h). These steps are followed by bacterial cell lysis by boiling, PCR oriented to inlB gene using a mimic internal control, and agarose gel electrophoresis. At the evaluation of the method on model food samples artificially contaminated with decimal dilutions of a L. monocytogenes culture (cheese, smoked fish, ready-to-eat meat products; 21 samples altogether), a detection limit of 100 cfu per 25 or 10 g was determined. Dead L. monocytogenes cells did not cause false positivity, as determined using model food samples artificially contaminated with decimal dilutions of dead L. monocytogenes cells. At the evaluation of the method on naturally contaminated food samples (same as above, 140 samples altogether) identical results (8 positives) as with the reference method were obtained.

Young children (4- to 7-years old; N = 59) and adults (N = 53) were shown a series of targets that were either familiar (i.e., popular cartoon characters) or unfamiliar (unknown human faces) to assess whether children’s false positive responding with target-absent lineups is driven by social factors to a greater degree than cognitive factors. Although children were able to produce correct identification rates with virtually 100% accuracy for the cartoon characters, they produced a significantly lower correct rejection rate compared to adults. Children also produced a significantly lower correct rejection rate for the human faces compared to adults. These data are discussed for understanding children’s identification evidence.

Information extraction from high spatial resolution imagery is sometimes hampered by the limited number of spectral channels available from these systems. Standard supervised classification algorithms found in commercial software packages may misclassify different features with similar spectral characteristics; leading to a high occurrence of false positives. An additional step in the information extraction process was developed incorporating the concept of object geometry. Objects are defined as a contiguous group of pixels identified as belonging to a single class in the spectral classification. Using results from the spectral classification, a supervised approach was developed using genetic programming to select and mathematically combine feature-specific shape descriptors from a larger set of shape descriptors, to form a new classifier. This investigation focused on extraction of residential housing from QuickBird and IKONOS imagery of the Mississippi Gulf Coast before and immediately after hurricane Katrina. Use of genetic programming significantly reduced false positives caused by asphalt pavement and isolated roofing material scattered throughout the image.

To face the worldwide threat of Surra caused by Trypanosoma evansi, international organizations have stressed the need to evaluate and standardize diagnostic tools. PCR detection of T. evansi has known a great expansion during the last 20 years, but primer sets are often insufficiently assessed and compared. In this work, we compared the performances of six primer pairs–TBR1/2 ( Masiga et al., 1992), ESAG6/7 ( 12 and 13), TEPAN1/2 ( Panyim et al., 1993), pMUTEC F/R ( Wuyts et al., 1994), TRYP1 R/S ( Desquesnes et al., 2001) and TRYP4 R/S (Desquesnes et al., unpublished)–tested with purified T. evansi DNA serial dilutions, T. evansi-infected rat blood serial dilutions and Thai dairy cattle samples.TBR1/2 primer set was able to detect 0.01 pg of purified DNA, and a parasitaemia below one parasite per ml in rat blood. They presented the highest sensitivity in cattle samples as well as a high specificity, without non-specific products nor false positive reactions out of 84 negative cattle samples tested. ESAG6/7 showed equivalent results with purified DNA and rat samples but presented non-specific products with Thai dairy cattle samples, leading to non interpretable results. TEPAN1/2 was not able to detect less than 0.1 pg of purified DNA or 50 trypanosomes/ml in rat blood. In cattle, TEPAN1/2 primers detected only 36% of the positives detected by TBR1/2. Given the parasitemic level detected, pMUTEC F/R, TRYP1 R/S and TRYP4 R/S were not more sensitive than classical microscopic examination of the buffy coat. TBR1/2, TEPAN1/2, pMUTEC F/R and TRYP4 R/S did not cross-reacted with Babesia sp., Trypanosoma theileri and Anaplasma marginale. TBR1/2 was the most sensitive primer set to detect T. evansi in purified DNA, rodent blood and cattle blood, and did not show cross reaction with the other pathogens tested: it should be therefore preferred for epidemiological surveys. These results confirmed that TBR1/2 primers remain the reference for the detection of Trypanozoon DNA and should therefore be included in subsequent evaluations of new diagnosis tools based on DNA detection.

The detection of concealed weapons at a distance is a critical security issue that has been a great challenge for different imaging approaches. In this paper we discuss the use of ultrasonics in a novel way to probe for metallic and non-metallic materials under clothing. ...

One of the common problems in the medical parasitology laboratory is the differentiation of parasites from other elements in the stool and body fluids so-called "artifacts". Artifacts generally referred to living or abiotic agents that embedded in the clinical sample and may misleading the lab because of their similarity to parasitic organisms. Artifacts are an integral part of the diagnosis process and they are cause of common misdiagnosis in the laboratory. Their differentiation from pathogenic parasitic agents is done by proper diagnosis, which leads to proper treatment of parasitic infections. As usually an inexperienced technician often misdiagnosed a yeast or other plant cell as amoeba or considers a platelet as a malaria parasite, it may be unsuccessful to identify parasitic organisms that really exist in the stool sample.  The major forms that cause confusion and misdiagnosis in parasitology laboratory are spores, fat droplets, yeast, red blood cells, and macrophages.Compared with other parts of the medical laboratory, in parasitology lab less attention observe  to this problem. The consequence is the reporting of false positive results, incorrect treatment, and patient injury.  Identifying, introducing, and differentiating artifacts for laboratory personnel, especially inexperienced, are an important factor in accurate diagnosis. In the present study, key diagnostic points of parasitic organisms and artifacts have been categories.

There were 13,176 roadside drug tests performed in the first year of the random drug-testing program conducted in the state of Victoria. Drugs targeted in the testing were methamphetamines and Delta(9)-tetrahydrocannabinol (THC). On-site screening was conducted by the police using DrugWipe, while the driver was still in the vehicle and if positive, a second test on collected oral fluid, using the Rapiscan, was performed in a specially outfitted "drug bus" located adjacent to the testing area. Oral fluid on presumptive positive cases was sent to the laboratory for confirmation with limits of quantification of 5, 5, and 2 ng/mL for methamphetamine (MA), methylenedioxy-methamphetamine (MDMA), and THC, respectively. Recovery experiments conducted in the laboratory showed quantitative recovery of analytes from the collector. When oral fluid could not be collected, blood was taken from the driver and sent to the laboratory for confirmation. These roadside tests gave 313 positive...