Diagnosing SARS-CoV-2 infection: the danger of over-reliance on positive test results

Abstract

Large-scale testing for SARS-CoV-2 by the reverse transcription polymerase chain reaction is a key part of the response to the COVID-19 pandemic, but little attention has been paid to the potential frequency and impacts of false positive results. In the absence of data on the clinical specificity of SARS-CoV-2 assays, we estimate a conservative false positive rate from external quality assessments of similar viral assays, and show that this rate may have large impacts on the reliability of positive test results. This has clinical and case management implications, affects an array of epidemiological statistics, and should inform the scale of testing and the allocation of testing resources. Measures to raise awareness of false positives, reduce their frequency, and mitigate their effects should be considered. outbreak of human coronavirus OC43 infection and serological crossreactivity with SARS coronavirus. Canadian Journal of Infectious Diseases and Medical Microbiology. 2006;17(6):330-6. 7 Koetz A, Nilsson P, Lindén MV, Van Der Hoek L, Ripa T. Detection of human coronavirus NL63, human metapneumovirus and respiratory syncytial virus in children with respiratory tract infections in south-west Sweden. Clinical microbiology and infection.

Detection of SARS-CoV-2 from Patient Fecal Samples by Whole Genome Sequencing

“…The exact rate of false positives has not been established for SARS-CoV-2, however in a study by Cohen and Kessel, the rate was extrapolated based on known false-positive rates from other viral RT-PCR tests. The mean false-positive rate in the study was found the be 3.2%, ranging from 0-16.7%, and an interquartile range of 0.8 to 4.0% [13].…”

Rapid detection of SARS-CoV-2 infection by multicapillary column coupled ion mobility spectrometry (MCC-IMS) of breath. A proof of concept study

“…Today RT-PCR is considered the gold standard in the diagnosis of SARS-CoV-2-infection but even in trained hands a false negative rate of about 25% and a false positive rate of 2.3-6.9% has to be expected. 15 According to the Editorial in Lancet Infectious Diseases May 2020 SARS-CoV-2 infections are rising in developing countries while declining in most of the western countries. In underdeveloped countries neither trained personal nor financial power to afford RT-PCR for mass screening can be assumed.…”

Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2): A Perspective Through the Lens of the Veterinary Diagnostic Laboratory

“…However, care must be taken to correctly interpret results and avoid false positive or negative results. False positive results can occur through cross-sample contamination during collection or testing (60)(61)(62). Confirmatory testing, ideally from a different laboratory, would increase confidence in positive results.…”

“…Virus isolation can verify that RNA equates to infectious virus in natural and experimental infections, but requires BSL-3 facilities and suitable cell lines for infection (e.g., Vero cells). False negative rRT-PCR results can be due to patient factors (e.g., intermittent shedding), sample collection (e.g., wrong timing, insufficient or inadequate specimens), sample handling (e.g., RNA degradation with storage), or test limitations (e.g., inadequate RNA extraction, insensitive primers, RNA levels below detection limits in early or low-level infections) (60)(61)(62). Viral RNA can be detected in situ using RNA hybridization and virus-specific probes in research studies (7,10,11,16,42).…”