CT suggests discharged Covid-19 patients who were retested RT-PCR positive again for SARS-CoV-2 more likely had false negative RT-PCR tests before discharging
Yi-Xiang Wang
Abstract
According to the Covid-19 discharging guideline in China, the patients ready for discharging should meet the following criteria: (I) body temperature is normal for more than 3 days; (II) obvious alleviation of respiratory symptoms; (III) remarkable absorption of lung lesions on chest imaging; (IV) two consecutive (with a 24-hour interval) negative RT-PCR tests for SARS-CoV-2 (1). In February this year it caused a lot of media coverage when four discharged Covid-19 patients were RT-PCR retested positive (RP) again for SARS-CoV-2 during their followup (FU) (2). However, since RT-PCR testing for SARS-CoV-2 is known to have certain range of false negative rate (3), simple logic would suggest these patients had false negative RT-PCR testing before discharging. The accuracy and predictive value of RT-PCR SARS-CoV-2 tests have not been systematically evaluated, while it is known that the sensitivity of RT-PCR testing depends on a number of factors including the precise RT-PCR assay, the type of specimen obtained, the quality of the specimen, and duration of illness at the time of testing (3). Simplistic statistic would suggest that, if RT-PCR false negative rate is 40%, then even if it is tested twice, a false negative rate of 16% would remain.