False positives in reverse transcription PCR testing for SARS-CoV-2

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.