Interpretations of a positive RT-PCR re-test
Considering the high infection rate, few cases of reinfection with SARS-CoV-2 have been reported. Often, for the diagnosis COVID-19 in a recovered individual a positive RT-PCR test with or without accompanying symptoms has been used. Although, in these cases different speculations for interpretation of a re-positivity can be made; each of which will have specific reverberations [21].
In some studies, a positive RT-PCR in a recovering patient who tested negative upon resolution of their symptoms, has been considered a strong indicator of reinfection [10]. Although, we should consider the possibility of a false result in either test [22]. A false positive result can occur in a recovering patient; also a false negative result shortly after subsidence of symptoms, followed by a correctly positive test misleads physicians towards a re-infection diagnosis [23]. To avoid this problem—as per WHO recommendations—in many regions the treatment protocol for COVID-19 requires two consecutive negative RT-PCR results prior to discharge [24, 25].
Also, RT-PCR cannot distinguish between replication-competent viruses and remnants of viral fragments that are expelled from a recovering patient [26, 27]. Viral shedding from the respiratory tract during the recovery period has been reported to last for as long as 12 weeks after infection [28]; thus, a significant time-gap between the first episode of infection and a positive RT-PCR test can clarify that the patient has passed the viral shedding stage.