Primary outcome
The primary outcome was the duration until conversion, which is defined as the time between the appearance of symptoms or the initial positive RT-PCR test and the second negative RT-PCR test outcome. From the second day of hospitalization onwards, all patients underwent daily RT-PCR testing using nasopharyngeal swabs until two consecutive negative results were obtained. According to China’s COVID-19 diagnosis and treatment guideline Trial Version 9, criteria for ending isolation and discharge involve obtaining two consecutive tests result with Ct values of ≥35 for ORF, N, and E genes with an interval of more than 24 hours[12, 18].