Properly collected plasma metanephrines excludes PPGL after false positive screening tests

Author(s):  
Gregory A Kline ◽  
Jessica Boyd ◽  
Brenda Polzin ◽  
Adrian Harvey ◽  
Janice L Pasieka ◽  
...  

Abstract Context False positive results are common for pheochromocytoma/paraganglioma(PPGL) real-world screening. Objective Determine the correlation between screening urine and seated plasma metanephrines in outpatients where PPGL was absent, compared to meticulously prepared and supine-collected plasma metanephrines with age-adjusted references. Design Retrospective cohort study Setting Databases from a single-provider provincial laboratory(2012-2018), a validated PPGL registry and a manual chart review from a specialized endocrine testing unit. Patients PPGL registry data excluded known PPGL cases from the laboratory database. Outpatients having both urine and plasma metanephrines <90 days apart. Methods The correlation between urine and seated plasma measures along with the total positivity rate. All cases of plasma metanephrines drawn in the endocrine unit were reviewed for test indication and test positivity rate. Results There were 810 non-PPGL pairs of urine and plasma metanephrines in the laboratory database; 46.1% of urine metanephrines were reported high. Of seated outpatient plasma metanephrines drawn a median of 5.9 days later, 19.2% were also high (r=0.33 and 0.50 for normetanephrine and metanephrine, respectively). In contrast, the meticulously prepared and supine collected patients(n=139, 51% prior high urine metanephrines) had <3% rate of abnormal high results in patients without known PPGL/adrenal mass. Conclusions There was a poor-to-moderate correlation between urine and seated plasma metanephrines. Up to 20% of those with high urine measures also had high seated plasma metanephrines in the absence of PPGL. Properly prepared and collected supine plasma metanephrines had a false positive rate of <3% in the absence of known PPGL/adrenal mass.

PEDIATRICS ◽  
1994 ◽  
Vol 94 (2) ◽  
pp. 174-179
Author(s):  
David J. Schonfeld ◽  
Mark R. Cullen ◽  
Petrie M. Rainey ◽  
Anne T. Berg ◽  
David R. Brown ◽  
...  

Objective. To assess the false positive rate of blood (BPb) determinations on sample obtained by fingerstick from children screened in an urban clinic. Method. From a single fingerstick (N = 1573), blood was collected in a capillary tube for determining lead concentration (CPb) by graphite furnace and an additional sample was absorbed onto a filter paper for determining lead concentration (FPb) by atomic absorption spectrophotometry with Delves cup. Zinc protoporphyrin (ZPP) was measured immediately and a confirmatory venous lead (VPb) specimen was obtained at the same visit if the ZPP was ≥35 µg/dL (0.6 µmol/L); children with either a CPb or FPb ≥15 µg/dL (0.7 µmol/L) were later recalled for determining VPb. Results. For the 172 children who had a VPb on the same day as the screening tests, the false positive rates (95% confidence intervals) at a lead threshold of 15 µg/dL (0.7 µmol/L) were: CPb, 13.5% (6.7-20.3); FPb, 19.1% (11.8-26.4). Analyses using all 679 screens with a paired venous specimen (mean delay between screen and venous testing = 30 days) yielded much higher false positive rates (CPb, 31.3%; FPb, 46.0%). Conclusions. Screening for lead poisoning is feasible within an urban pediatric clinic by direct measurement of lead concentration in blood samples obtained by fingerstick. The false positive rate that can be obtained is acceptable given the precision of measuring BPb concentration. Practitioners using a staged screening protocol may incorrectly attribute a higher false positive rate to the screening tests, when much of the error may be due to the temporal variability of BPb resulting from both biologic variability in BPb concentration and intermittent exposures.


2018 ◽  
Vol 5 (1) ◽  
pp. 171511 ◽  
Author(s):  
David Robert Grimes ◽  
Chris T. Bauch ◽  
John P. A. Ioannidis

Scientific publication is immensely important to the scientific endeavour. There is, however, concern that rewarding scientists chiefly on publication creates a perverse incentive, allowing careless and fraudulent conduct to thrive, compounded by the predisposition of top-tier journals towards novel, positive findings rather than investigations confirming null hypothesis. This potentially compounds a reproducibility crisis in several fields, and risks undermining science and public trust in scientific findings. To date, there has been comparatively little modelling on factors that influence science trustworthiness, despite the importance of quantifying the problem. We present a simple phenomenological model with cohorts of diligent, careless and unethical scientists, with funding allocated by published outputs. This analysis suggests that trustworthiness of published science in a given field is influenced by false positive rate, and pressures for positive results. We find decreasing available funding has negative consequences for resulting trustworthiness, and examine strategies to combat propagation of irreproducible science.


2014 ◽  
Vol 77 (2) ◽  
pp. 308-313 ◽  
Author(s):  
M. C. BELTRÁN ◽  
M. BORRÀS ◽  
O. NAGEL ◽  
R. L. ALTHAUS ◽  
M. P. MOLINA

The suitability of different receptor-binding assays to detect antibiotics in raw goat's milk was investigated. Detection capability of most β-lactams and tetracyclines assessed applying the Betastar Combo, the SNAP Betalactam, the SNAP Tetracycline, and the Twinsensor tests was at or below maximum residue limits established by European legislation. Regarding test specificity, cross-reactions with antibiotics other than β-lactams and tetracyclines were not found, and no false-positive results were obtained for the Betastar Combo and the SNAP tests when bulk samples of goat's milk were analyzed. For the Twinsensor test, the false-positive rate was 1%. The performance of the Betastar Combo and the SNAP tests was practically unaffected by the milk quality parameters using individual samples of goat's milk collected at points throughout the entire lactation period (false-positive rate, ≤5%). However, a larger number of positive results were obtained by the Twinsensor test in this type of milk sample (>10%), especially in the last weeks of lactation. Interferences related to the use of the preservative azidiol were not observed in any case. Neither were any significant differences found in relation to the interpretation method (visual versus instrumental) applied. In general, the response of the Betastar Combo, SNAP, and Twinsensor tests was optimal for the analysis of bulk caprine milk; thus, they may be used to monitor milk for the presence of β-lactam and tetracycline residues in quality control programs.


2007 ◽  
Vol 73 (19) ◽  
pp. 6296-6298 ◽  
Author(s):  
Hui-Zin Tu ◽  
Chiao-Shan Chen ◽  
Tsi-Shu Huang ◽  
Wen-Kuei Huang ◽  
Yao-shen Chen ◽  
...  

ABSTRACT A point-of-use 0.2-μm filter was evaluated for elimination of nontuberculosis mycobacteria in laboratory water to reduce false-positive acid-fast bacillus staining results. Use of the point-of-use filter can significantly reduce the false-positive rate to 1.2% compared to samples treated with tap water (10.7%) and deionized water (8.7%).


2005 ◽  
Vol 13 (3) ◽  
pp. 151-153 ◽  
Author(s):  
David J. Garry ◽  
Andrew Elimian ◽  
Vandy Wiencek ◽  
David A. Baker

Objective.This study was performed to review the clinical utility of commercial laboratoryToxoplasmosis-specific IgM testing during pregnancy and outcomes of the gestation at our institution.Methods.A retrospective review of all women referred for suspected acuteToxoplasma gondiiinfection during pregnancy from 1984 through 2004 was performed. Women were diagnosed with suspected acute toxoplasmosis based on commercial laboratory serologic antibody testing. All women had blood sent to a recognized reference laboratory for antibody testing within 2 weeks of the commercial laboratory results. The study protocol was approved by the Institutional Review Board. Chi-square analysis were used with a significance ofP< .05.Results.A total of 130 women were evaluated during the study period with 116 IgM positive results from the commercial laboratories. The commercial laboratory antibodies were as follows: IgM positive with IgG negative (n= 20), IgM positive with IgG positive (n= 96), and IgM negative with IgG positive (n= 14). There was a significant reduction in the IgM positive results when comparing commercial laboratory (n= 116) with the reference laboratory results (n= 28;p< .001). Acute toxoplasmosis infection was diagnosed in 7 (5%) of the women. All cases of acute toxoplasmosis infection had a positive commercial laboratory IgM result. The false positive rate for the commercial laboratory IgM was 88.6% and the diagnostic indices were sensitivity 100%, specificity 11.4%, positive predictive value 6% and negative predictive value 100%.Conclusion.Commercial laboratoryToxoplasmosis-specific IgM is associated with a high false positive rate. The commercial and reference laboratory IgM results identified all cases of acute toxoplasmosis infection. Commercial laboratories reflexively obtaining reference laboratory confirmation of positive results could reduce costs associated with testing, referrals, retesting, and invasive procedures.


2019 ◽  
Author(s):  
Karina Bilda De Castro Rezende ◽  
Antonio José Ledo Alves Cunha ◽  
Joffre Amim Jr ◽  
Wescule De Moraes Oliveira ◽  
Maria Eduarda Belloti Leão ◽  
...  

BACKGROUND FMF2012 is an algorithm developed by the Fetal Medicine Foundation (FMF) to predict pre-eclampsia on the basis of maternal characteristics combined with biophysical and biochemical markers. Afro-Caribbean ethnicity is the second risk factor, in magnitude, found in populations tested by FMF, which was not confirmed in a Brazilian setting. OBJECTIVE This study aimed to analyze the performance of pre-eclampsia prediction software by customization of maternal ethnicity. METHODS This was a cross-sectional observational study, with secondary evaluation of data from FMF first trimester screening tests of singleton pregnancies. Risk scores were calculated from maternal characteristics and biophysical markers, and they were presented as the risk for early pre-eclampsia (PE34) and preterm pre-eclampsia (PE37). The following steps were followed: (1) identification of women characterized as black ethnicity; (2) calculation of early and preterm pre-eclampsia risk, reclassifying them as white, which generated a new score; (3) comparison of the proportions of women categorized as high risk between the original and new scores; (4) construction of the receiver operator characteristic curve; (5) calculation of the area under the curve, sensitivity, and false positive rate; and (6) comparison of the area under the curve, sensitivity, and false positive rate of the original with the new risk by chi-square test. RESULTS A total of 1531 cases were included in the final sample, with 219 out of 1531 cases (14.30; 95% CI 12.5-16.0) and 182 out of 1531 cases (11.88%; 95% CI 10.3-13.5) classified as high risk for pre-eclampsia development, originally and after recalculating the new risk, respectively. The comparison of FMF2012 predictive model performance between the originally estimated risks and the estimated new risks showed that the difference was not significant for sensitivity and area under the curve, but it was significant for false positive rate. CONCLUSIONS We conclude that black ethnicity classification of Brazilian pregnant women by the FMF2012 algorithm increases the false positive rate. Suppressing ethnicity effect did not improve the test sensitivity. By modifying demographic characteristics, it is possible to improve some performance aspects of clinical prediction tests.


Chemotherapy ◽  
2018 ◽  
Vol 63 (6) ◽  
pp. 324-329 ◽  
Author(s):  
Michael S. Ewer ◽  
Jay Herson

Purpose: Cardiac ultrasound provides important structural and functional information that makes identification of cardiac abnormalities possible. Left ventricular ejection fraction (LVEF) provides the most commonly used parameter for recognition of treatment-related cardiac dysfunction. Random reading variance and physiologic factors influence LVEF and make the reported value imperfect. We attempt to quantitate the likelihood of false positive events by computer simulation. Methods: We simulated four visits on hypothetical trials. We assumed a baseline LVEF of 55% and normal distribution with regard to reading error and physiologic variation. 1,000 trials of sample size 1,500 were simulated. In a separate simulation, 1,000 patients entered with LVEFs of 45, 43, and 41% to estimate true positive incidence. Results: At each examination, less than 1.0% of false positives were noted. The cumulative false positive rate over four visits was 3.60%. True cardiotoxicity identification is satisfactory only when LVEF declines substantially. Conclusion: A 3.60% false positive rate in trials where the expected level of toxicity is low suggests that false positives are troubling and may exceed true positive results. Strategies to reduce the number of false positive results include making confirmatory studies mandatory. Evaluating increases along with decreases obtains some estimation of variance.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xiaolan Lu ◽  
Minghong Zhang ◽  
Wen Liu ◽  
Nan Sheng ◽  
Qin Du ◽  
...  

AbstractTo explore the effects of urea dissociation on reducing false-positive results of  the Elecsys HIV combi PT assay. A retrospective analysis was used to evaluate the false-positive rate of the Elecsys HIV combi PT assay. Six false-positive sera, six positive sera and six sera from patients with early HIV infection were collected. Dissociation was performed using 1 mol/L, 2 mol/L, 4 mol/L, 6 mol/L, or 8 mol/L urea, and HIV screening assay were then detected to select the appropriate concentration of urea dissociation. Next, 55 false-positive sera and 15 sera from early HIV infection were used to verify the best concentration of urea to achieve dissociation. Retrospective analysis showed that the COI of the Elecsys HIV combi PT assay in false-positive sera ranged from 1.0 to 200.0, and approximately 97.01%(227/234) of false-positive sera were in the range of 1.0–15.0. The avidity index (AI) in positive and false-positive sera decreased as the urea dissociation concentration increased. When the dissociation concentration was 6 mol/L, the AI of false-positive serum was between 0.0234 and 0.2567, and the AI of early HIV infection sera was between 0.4325 and 0.5017. The difference in AI between false-positive and positive samples was significant. When negativity was defined as an AI of less than 0.3970, the sensitivity and specificity were 100.0% and 100.0%, respectively. Urea-mediated dissociation could significantly reduce the false-positive rate of the Elecsys HIV combi PT assay with a low COI. Our findings provided a reference for distinguishing positive and false-positive of the Elecsys HIV combi PT assay.


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1900-1900
Author(s):  
Jennifer Rhamy ◽  
Mark Beltz ◽  
Karla John ◽  
David Feria ◽  
Dan Waxman ◽  
...  

Abstract Introduction: Donors of cord blood (CBD) are screened similarly to whole blood donors (WBD). It has been reported that CBD have a higher incidence of both true positive and false positive disease markers tested by EIA[1]. This abstract compares the rate of positive results for viral RNA (NAT) in CBD vs. WBD in a large cohort of donors. Methods: NAT was performed using the Chiron Procleix MPX or discriminatory assays. EIA testing was performed using Abbott bead methodology following manufacturer’s instructions. Confirmatory results for EIA were performed with Chiron RIBA. Results from 12/17/04 to 6/30/05 were collated. Results EIA HIV EIA HCV NAT HIV/HCV HIV EIA POS(%) HCV EIA POS (%) HIV NAT POS HCV NAT POS WBD 74299 74299 74299 75(0.10) 107(0.14) 1 (0) 31(0.04) CBD 11996 12001 12007 50(0.42) 46(0.38) 0 13 (0.11) A higher percentage of CBD were positive for HIV and HCV EIA as previously reported1. HIV NAT positive donors were 0.00% for both populations. The ratio of HCV EIA positive to HCV NAT positive donors was 28.97% for WBD and 28.26% in CBD. The ratio of CBD HCV EIA positives to WBD HCV EIA positives is 2.71 and the ratio of WBD HCV NAT positives to WBD HCV NAT positives is 2.75. The ratio of HIV CBD EIA positives to HIV WBD EIA positives is 4.10, which is significantly higher (p=<0.01). Conclusions Both CBD and WBD have a low rate (0%) of HIV NAT positive donors, but CBD have a 4x higher rate of HIV EIA. This suggests a 4x higher donor loss to false positive antibody results. The CBD donors have a 2.7x higher rate for both EIA and NAT positive results, showing a higher rate of viremic donors in CBD. The similar ratios for EIA positive to NAT positive donors in the two populations suggest that the false positive rate is not elevated in CBD versus WBD. The higher incidence of HCV infection in CBD could be geographic or ethnic in origin. More study is needed to determine the reasons and further predict donor loss. The HIV EIA results are not predictive of actual infection in this population. A more aggressive logarithm for reentry than used for WBD may be merited.


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