One in five viral COVID-19 tests deliver false negative results — and sometimes the failure rate is far worse, according to Johns Hopkins University researchers.
The tests used to diagnose current COVID-19 infections — called reverse transcriptase polymerase chain reaction tests — may not always yield accurate results. And timing appears to be closely linked to reliability, wrote Lauren Kucirka, M.D., Ph.D., and colleagues.
In an analysis of published studies, investigators found that the probability of a false negative result from these RT-PCR tests changes over the course of the illness. For example, the likelihood of a false negative decreased from 100% on the first day of infection to 67% on day four, and to 20% on day eight (three days after obvious symptoms develop). The odds of an incorrect reading then rose again three weeks into the illness. Notably, on the first day of evident symptoms, the average false negative rate was found to be 38%.
The takeaway? Clinicians should use caution when interpreting negative RT-PCR test results, particularly for individuals who have been exposed to or who have symptoms of COVID-19, the researchers concluded.
Full findings were published in the Annals of Internal Medicine.
