• Yu Fu, Yongsheng Li, Ensong Guo, Liang He, Jia Liu, Bin Yang, Fuxia Li, Zizhuo Wang, Yuan Li, Rourou Xiao, Chen Liu, Yuhan Huang, Xue Wu, Funian Lu, Lixin You, Tianyu Qin, Chaolong Wang, Kezhen Li, Peng Wu, Ding Ma, Chaoyang Sun, and Gang Chen.
• National Clinical Research Center for Gynecology and Obstetrics and Cancer Biology Research Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China (Y.F., E.G., L.H., J.L., B.Y., F.L., Z.W., Y.L., R.X., C.L., Y.H., X.W., F.L., L.Y., T.Q., K.L., P.W., D.M., C.S., G.C.).
• Ann. Intern. Med. 2021 Apr 1; 174 (4): 453-461.

BackgroundThe understanding of viral positivity and seroconversion during the course of coronavirus disease 2019 (COVID-19) is limited.ObjectiveTo describe patterns of viral polymerase chain reaction (PCR) positivity and evaluate their correlations with seroconversion and disease severity.DesignRetrospective cohort study.Setting3 designated specialty care centers for COVID-19 in Wuhan, China.Participants3192 adult patients with COVID-19.MeasurementsDemographic, clinical, and laboratory data.ResultsAmong 12 780 reverse transcriptase PCR tests for severe acute respiratory syndrome coronavirus 2 that were done, 24.0% had positive results. In 2142 patients with laboratory-confirmed COVID-19, the viral positivity rate peaked within the first 3 days. The median duration of viral positivity was 24.0 days (95% CI, 18.9 to 29.1 days) in critically ill patients and 18.0 days (CI, 16.8 to 19.1 days) in noncritically ill patients. Being critically ill was an independent risk factor for longer viral positivity (hazard ratio, 0.700 [CI, 0.595 to 0.824]; P < 0.001). In patients with laboratory-confirmed COVID-19, the IgM-positive rate was 19.3% in the first week, peaked in the fifth week (81.5%), and then decreased steadily to around 55% within 9 to 10 weeks. The IgG-positive rate was 44.6% in the first week, reached 93.3% in the fourth week, and then remained high. Similar antibody responses were seen in clinically diagnosed cases. Serum inflammatory markers remained higher in critically ill patients. Among noncritically ill patients, a higher proportion of those with persistent viral positivity had low IgM titers (<100 AU/mL) during the entire course compared with those with short viral positivity.LimitationRetrospective study and irregular viral and serology testing.ConclusionThe rate of viral PCR positivity peaked within the initial few days. Seroconversion rates peaked within 4 to 5 weeks. Dynamic laboratory index changes corresponded well to clinical signs, the recovery process, and disease severity. Low IgM titers (<100 AU/mL) are an independent risk factor for persistent viral positivity.Primary Funding SourceNone.

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