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.