Real-time RT-PCR for the detection of SARS-CoV-2 nucleic acid

Abstract

Objective To investigate the performance of real-time RT-PCR for the detection of SARS-CoV-2 nucleic acid in clinical diagnosis of COVID-2019. Methods Laboratory test data and basic case information of Henan COVID-19 cases were collected from the China's Infectious Disease Information System as of March 5, 2020. All information was entered by local hospitals and Center for Disease Control and Prevention (CDC). Local hospitals or country CDC were responsible for sampling and municipal CDC was responsible for nucleic acid testing. Results A total of 6 714 specimens were detected and the positive rate of SARS-CoV-2 nucleic acid was 23.82%. The specimens were collected from 1 200 confirmed cases, 2 178 suspected cases and 77 asymptomatic cases. The nucleic acid diagnosis rate of COVID-19 was 36.96% (1 277/3 455). In all cases, the positive rates of SARS-CoV-2 nucleic acid in nasal swabs, sputum samples and throat swabs were 19.38%, 28.59% and 23.53%, respectively (χ2=15.896, P<0.01). The positive rate of SARS-CoV-2 nucleic acid in confirmed COVID-19 cases was 63.10%. The positive rates in nasal swabs, sputum samples and throat swabs were 50.80%, 58.71% and 65.21 (χ2=18.612, P<0.01). The positive rates of SARS-CoV-2 nucleic acid were 43.51%, 23.98%, 22.82%, 12.17%, 14.46% and 13.21% in samples collected on the day of symptom onset and one week, two weeks, three weeks, four weeks, five weeks and above five weeks after the onset, respectively. The positive rates in confirmed cases were respectively 89.03%, 86.57%, 52.30%, 17.53%, 17.69% and 24.14% at those time points. Conclusions Real-time RT-PCR is the most effective method for early pathogenic diagnosis of COVID-19. The highest detection rate of nucleic acid is achieved within one week after the onset of COVID-19, and the latest time for nucleic acid detection is 38 d after the onset. Key words: SARS-CoV-2; COVID-19; Real-time RT-PCR