Variation in False-Negative Rate of RT-PCR–Based SARS-CoV-2 Tests by Time Since Exposure

TAKE-HOME MESSAGE

Understanding the variation of predictive value of reverse transcriptase polymerase chain reaction (RT-PCR) tests for SARS-CoV-2 with time from exposure and symptom onset is critically important. Such knowledge would help to avoid false-negative results from the tests that are performed early in the infection trajectory. Hence, this study used literature review and pooled analysis to assess a day-wise false-negative rate since the start of the infection.

The authors advise exercising caution with interpretation of RT-PCR tests for SARS-CoV-2 infection, especially in the earlier stages of infection and when these results would be used for guiding removal of precautions for transmission prevention. In case of a greater degree of clinical suspicion, an infection should not be ruled out based on the results of this test alone. It is equally important to consider the epidemiology as well since time of exposure could be unknown and the tests are usually performed after symptom onset. Since the false-negative rate appears to be lowest at 3 days after symptom onset or around 8 days after exposure, it is advisable to wait for 1 to 3 days after symptom onset to lessen the likelihood of a false-negative result.