Definition and Confirmation of Positive Retest Patients
This study refers to discharged patients who tested positive for
SARS-CoV-2 again using RT-PCR as positive retest patients. Based on open
reading frame 1ab (ORF 1ab) and nucleocapsid (N) protein genes in the
SARS-CoV-2 genome, RT-PCR was performed to assess the results(Corman et
al., 2020; Luo, Liu, Zhang, et al., 2020). If the cycle threshold (Ct)
value of RT-PCR is less than 37, the sample is positive; if the Ct value
ranges between 37 and 40, and if the amplification curve has an obvious
peak, then the sample is considered positive. Otherwise, the sample is
considered as negative.
The following three conditions are considered positive. First, the two
targets, ORF 1ab and N protein, are both positive. Second, in case of
the result showing positivity for one target, samples shall be
recollected for another test. If it is still positive for a single
target, the result should be considered positive. Third, if two types of
specimens show one single target as positive at the same time or if one
target is positive in two samples of the same type, then the result
should be considered positive.