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.