Study population and setting
173 cases of COVID-19 from the Shenzhen Third People’s Hospital (Guangdong Province, China) between January 11, 2020 and February 9, 2020. Patients had acute respiratory infection syndromes and/or abnormalities in chest computed tomography (CT) images with a detectable SARS-CoV-2 RNA in a respiratory sample for at least one time point. Critical illness (n=32) was defined as acute respiratory distress syndrome or oxygen saturation <93% who required mechanical ventilation either invasively or non-invasively.
Summary of Main Findings
Sensitivity of RT-PCR on nasal swabs is at most ~70%, 3 to 5 days post symptoms and decreases to 40% by day 9. 90% of individuals seroconvert 15 days after symptoms. The average time from symptoms to seroconversion was 11 days. Individuals with critical illness had higher concentrations of antibodies to SARS-CoV-2.
Large sample size and good follow up data.
RT-PCR was performed on nasal swabs.
Demonstrates that sensitivity of RT-PCR of nasal swabs is highly dependent on the timing of sampling.