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 (
oropharynx
,SARS-CoV-2
,COVID-19
,reproducibility of results
,humans
,false negative reactions
,probability
,COVID-19 nucleic acid testing
,sensitivity and specificity
,reverse transcriptase polymerase Chain Reaction
,time factors
,nasopharynx
