Objective To investigate positive rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid and antibody of different biological samples from diagnosed coronavirus disease 2019 (COVID-19) patients.
Methods A variety of biological samples were collected from 101 confirmed COVID-19 cases and 35 asymptomatic infected persons in Dongguan city, Guangdong province from January 23 to October 9, 2020. SARS-CoV-2 nucleic acid was detected with real-time fluorescence quantitative reverse transcriptase polymerase chain reaction (RT-PCR); serum immunoglobulin M (IgM) and IgG antibodies against SARS-CoV-2 were measured with colloidal gold method. The detection results were analyzed statistically.
Results The median duration of persistent positivity of SARS-CoV-2 nucleic acid the was 7.00 days (interquartile range: 0.00 – 27.00 days) for all the patients. Within 0 – 7 days after the onset of COVID-19, the positive rates were 48.21% (121/251), 36.00% (9/25), and 31.82% (7/22) for pharyngeal, anal, and nasopharyngeal swab specimens, respectively. No SARS-CoV-2 nucleic acid positive urine samples were detected during whole course of the disease for all the patients. SARS-CoV-2 nucleic acid positive pharyngeal, anal, and nasopharyngeal swab specimens were detected but no positive sputum and feces samples were detected among the asymptomatic patients.
Conclusion With the progress of disease, the positive rate of SARS-CoV-2 nucleic acid decreases for pharyngeal, anal, and nasopharyngeal swab specimens from COVID-19 patients but that of serum IgG antibody against SARS-CoV-2 increases.
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