The Dangers of False-Positive and False-Negative Test Results: False-Positive Results as a Function of Pretest Probability

During the last 3 years, random urine samples from 408 patients were tested for elevated homovanillic acid (HVA) and vanillylmandelic acid (VMA) levels to rule out the diagnosis of neuroblastoma. Thirty-seven of these patients had elevated HVA and/or VMA levels, and neuroblastoma was subsequently diagnosed. In three additional patients with negative test results (normal HVA and VMA levels), tumors were subsequently diagnosed (false-negative rate of 7.5%). Ten percent of the patients with neuroblastoma had normal HVA and 27.5% had normal VMA levels at the time of diagnosis. Only one patient (2.5%) with neuroblastoma had elevated VMA levels in the presence of normal HVA levels. More than 60% of the patients with neuroblastoma had urinary HVA and/or VMA levels higher than twice the upper limit of normal. No false-positive results were encountered. Age and stage distributions of the patients are shown, and the significance of the results is discussed.

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Incidence and Recovery of Salmonellae and Other Bacteria from Commercially Processed Poultry Carcasses at Selected Pre- and Post-Evisceration Steps

Journal of Food Protection ◽

10.4315/0362-028x-52.2.88 ◽

1989 ◽

Vol 52 (2) ◽

pp. 88-91 ◽

Cited By ~ 71

Author(s):

H. S. LILLARD

Keyword(s):

False Negative ◽

Aerobic Bacteria ◽

Processing Plant ◽

Test Results ◽

Negative Test ◽

Commercial Plant ◽

Sampling Points ◽

Processing Line ◽

False Negative Test ◽

Progressive Sampling

This study was undertaken to determine whether bacteria are already attached to poultry skin when birds arrive at the processing plant. Multiple rinses were performed on breast skin and whole carcasses taken from five processing points in a commercial plant: Before scalding, after scalding, after picking, after the final washer, and from the exit end of the chiller. Aerobic bacteria and Enterobacteriaceae were recovered from carcasses in up to 40 consecutive whole carcass rinses with a difference of only about one log for Enterobacteriaceae, and 1 to 2 logs for aerobes from the first to the last rinse of carcasses taken from the beginning and the end of the processing line. Data from rinses prior to scalding indicated that bacteria were firmly attached to poultry carcasses when they first arrived in the plant. Not all bacteria were removed during processing; however, there were fewer aerobes and Enterobacteriaceae at progressive sampling points. Attached salmonellae were not always recovered in the first whole carcass rinse, but were sometimes recovered in 3rd, 5th, and 10th rinses. These data show that a single whole carcass rinse can result in false negative test results for salmonellae. Because of the small number of positive samples in this study, the probability of recovering salmonellae with a single whole carcass rinse could not be estimated accurately.

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Estimating the false-negative test probability of SARS-CoV-2 by RT-PCR

Eurosurveillance ◽

10.2807/1560-7917.es.2020.25.50.2000568 ◽

2020 ◽

Vol 25 (50) ◽

Author(s):

Paul S Wikramaratna ◽

Robert S Paton ◽

Mahan Ghafari ◽

José Lourenço

Keyword(s):

Symptom Onset ◽

False Positive ◽

False Negative ◽

Positive Test ◽

Rt Pcr ◽

Negative Test ◽

False Positive Test ◽

True Number ◽

Test Probability ◽

False Negative Test

Background Reverse-transcription PCR (RT-PCR) assays are used to test for infection with the SARS-CoV-2 virus. RT-PCR tests are highly specific and the probability of false positives is low, but false negatives are possible depending on swab type and time since symptom onset. Aim To determine how the probability of obtaining a false-negative test in infected patients is affected by time since symptom onset and swab type. Methods We used generalised additive mixed models to analyse publicly available data from patients who received multiple RT-PCR tests and were identified as SARS-CoV-2 positive at least once. Results The probability of a positive test decreased with time since symptom onset, with oropharyngeal (OP) samples less likely to yield a positive result than nasopharyngeal (NP) samples. The probability of incorrectly identifying an uninfected individual due to a false-negative test was considerably reduced if negative tests were repeated 24 hours later. For a small false-positive test probability (<0.5%), the true number of infected individuals was larger than the number of positive tests. For a higher false-positive test probability, the true number of infected individuals was smaller than the number of positive tests. Conclusion NP samples are more sensitive than OP samples. The later an infected individual is tested after symptom onset, the less likely they are to test positive. This has implications for identifying infected patients, contact tracing and discharging convalescing patients who are potentially still infectious.

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False-negative test results to non-agglutinating (incomplete) antibodies.

Sexually Transmitted Infections ◽

10.1136/sti.58.4.275-c ◽

1982 ◽

Vol 58 (4) ◽

pp. 275-276

Author(s):

E de Klerk ◽

C A Sharp ◽

C Geffen ◽

R Anderson

Keyword(s):

False Negative ◽

Test Results ◽

Negative Test ◽

False Negative Test

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Quantified scoring of the amniotic fluid surfactant foam test and assessment of factors contributing to false negative test results

American Journal of Obstetrics and Gynecology ◽

10.1016/0002-9378(83)90586-0 ◽

1983 ◽

Vol 145 (6) ◽

pp. 752-756 ◽

Cited By ~ 1

Author(s):

Neil S. Whitworth ◽

John C. Morrison ◽

Amy C. Whitton ◽

Karen K. Bowers

Keyword(s):

Amniotic Fluid ◽

False Negative ◽

Test Results ◽

Negative Test ◽

False Negative Test

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RE: “PROBABILITY OF INTRODUCING DISEASES BECAUSE OF FALSE NEGATIVE TEST RESULTS”

American Journal of Epidemiology ◽

10.1093/oxfordjournals.aje.a115882 ◽

1991 ◽

Vol 133 (3) ◽

pp. 321-321 ◽

Cited By ~ 4

Author(s):

Margaret A. Thorburn ◽

John J. McDermott ◽

S. Wayne Martin

Keyword(s):

False Negative ◽

Test Results ◽

Negative Test ◽

False Negative Test

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COVID-19 Testing: Challenges, Limitations and Suggestions for Improvement

10.20944/preprints202004.0155.v1 ◽

2020 ◽

Cited By ~ 1

Author(s):

Emily Hu

Keyword(s):

False Negative ◽

Diagnostic Methods ◽

Test Results ◽

Successful Management ◽

Negative Test ◽

Reliable Methods ◽

False Negative Test

Reliable methods to confirm the diagnosis of COVID-19 are essential to the successful management and containment of the virus. Current diagnostic options are limited in type, supply, and reliability. This article explores the controversial unreliability of existing diagnostic methods and maintains that more reliable diagnostic methods, combinations, and sequencing are necessary to effectively assist in reducing the occurrence of discharge of the patient on false negative test results. This reduction would in effect reduce transmission of the disease.

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