Nucleic acid detection results analysis in different COVID-19 samples

Objective To understand the results and influencing factors of SARS-CoV-2 nucleic acid detection among specimens in different types and stages of coronavirus disease 2019 (COVID-19) progression. Methods The samples of deep-tussive sputum, pharyngeal swab, stool and conjunctival swab were collected among the suspected cases and close contacts of COVID-19 in Guilin. The SARS-CoV-2 RNAs were detected using double fluorescence real-time RT-PCR. The epidemiology, clinical diagnosis and laboratory data were collected to analyze the factors of improving the sensitivity of nucleic acid detection. Results A total of 654 samples were collected among 537 suspected cases and close contacts, including 569 deep-tussive sputum, 26 pharyngeal swabs, 28 stool and 31 conjunctival swabs. Thirty-two SARS-CoV-2 nucleic acid positive cases were found, with a nucleic acid positive rate of 6.00% (32/537). The median days (range) of the first nucleic acid positive deep-tussive sputum sampling time from onset day of illness were 0-23 days. The SARS-CoV-2 nucleic acid positive rate of deep-tussive sputum was significantly higher than that of pharyngeal swabs ( P =0.000). The SARS-CoV-2 nucleic acid positive number of stool and conjunctival swabs were 19 cases and 5 cases, respectively, which their sampling time were the average 7 days later than that of the first sampling deep-tussive sputum with SARS-CoV-2 positive. Among the 32 confirmed cases of COVID-19, there were 28 cases collected a single sample of deep-tussive sputum with SARS-CoV-2 nucleic acid positive, which samples of 6 cases, 6 cases, 3 cases, 4 cases and 9 cases were collected on the first day, 2nd day, 3rd day, 4th day, 5th day and above, respectively. In 4 cases, samples of deep-tussive sputum should be collected twice or more before nucleic acid positive results. Before sampling, one case had a history of fever and treatment. As a close contact, two samples of deep-tussive sputum were collected on the 21st day and 23rd day from onset day of illness, with SARS-CoV-2 nucleic acid negative and positive, respectively. Conclusions The deep-tussive sputum is better than pharyngeal swab in the detection of SARS-CoV-2 nucleic acid, and the SARS-CoV-2 nucleic acid positive can also be detected by stool and conjunctival swab. The sampling type, sampling time and treatment history are the influencing factors of the sensitivity of SARS-CoV-2 nucleic acid detection. So as not to miss detection, suspected cases or close contacts should be isolated observation and multiple sampling detection. 摘要：目的 了解不同类型和疾病进展阶段新型冠状病毒肺炎(coronavirus disease 2019,COVID-19)病例的标本新 型冠状病毒(SARS-CoV-2)核酸检测结果及影响因素。 方法 对桂林市新型冠状病毒肺炎疑似病例及密切接触者分 别采集深咳痰液、咽拭子、粪便及眼结膜拭子,采用双重实时荧光RT-PCR方法进行SARS-CoV-2核酸检测,收集流行 病学、临床实验室及辅助诊断等资料,分析提髙核酸检测敏感性的因素。 结果 共采集537例COVID-19疑似病例及 密切接触者标本654份,其中,深咳痰液569份,咽拭子26份,粪便28份,眼结膜拭子31份。SARS-CoV-2核酸阳性32 例,核酸阳性检出率6.00%(32/537);首次核酸阳性的深咳痰液的采样时间与发病时间的间隔天数0〜23 d。在2种样本 检测比较中,深咳痰液中SARS-CoV-2核酸阳性检出率明显髙于咽拭子标本的检出率( P =0.000)。粪便和眼结膜拭子 中SARS-CoV-2核酸阳性分别有19例和5例,它们的采样时间与首次核酸阳性的深咳痰液样本的采样时间比较平均 晚7 d。在32例新型冠状病毒肺炎确诊病例中,28例单次采集深咳痰液样本为核酸阳性,其中,于发病第1、2、3、和5 d 及以上分别有6、6、3、4和9例；4例病例需采集2次及以上深咳痰液样本才出现核酸阳性结果。1例病例在采样前有发 热及治疗史,作为密切接触者排査隔离观察,分别于发病后第21天（阴性）、第23天（阳性)采集2份深咳痰液标本检测。 结论 SARS-CoV-2核酸检测中深咳痰液标本优于咽拭子标本,粪便和眼结膜拭子也可检测到病毒核酸,采样方式、采 样时机及治疗史为核酸检测敏感性的影响因素,对疑似病例或密切接触者需隔离观察并多次采样检测,以免漏检。