Analysis of novel coronavirus nucleic acid detection in different specimens of COVID-19 patients after treatment in Tianjin

ABSTRACT

Objective: To retrospectively analyze the test results of novel coronavirus (2019-nCoV) in different samples (throat swab, sputum and feces) collected from recovered COVID-19 patients in order to provide a more reliable basis for discharge and reduce the risk of recurrence after discharge. Methods: Throat swabs and sputum were sampled in pairs from 78 patients before discharge and sampled in pairs twice from 54 cases with an interval of 1-5 d. Real-time fluorescence quantitative RT-PCR was used to detect the virus in the two types of samples. Throat swab, sputum and fecal samples of six patients were tested for 2019-nCoV during follow-up. Results: The detection rate of viral nucleic acid was 46.15% in throat swabs and 50.00% in sputum samples. Test results of the second paired samples showed that the detection rate of viral nucleic acid was 25.93% in throat swabs and 46.30% in sputum samples, and the difference between the two types of samples was statistically significant (P<0.05). During follow-up, 2019-nCoV nucleic acid could be detected in the fecal samples of the six patients, but not in their throat swab and sputum samples. Their fecal samples remained positive up to 52 d. Conclusions: In the late convalescence, the respiratory symptoms of COVID-19 patients gradually disappeared with the improvement of clinical symptoms. Moreover, the virus might enter the gastrointestinal tract from respiratory tract, and could long-term exist in recovered patients and be excreted in feces. In order to reduce the rate of missed detection and avoid false negative results, it was suggested to test the viral nucleic acid in different types of samples before a COVID-19 patient was discharged.