A comparative study of SARS-COV-2 nucleic acid assay for nasal swab and sputum samples

Abstract

Objective To analyze nucleic acid detection results of coronavirus disease 2019 (COVID-19) patients' nasal swabs and sputum specimens, and we provide reference for clinical sampling methods. Methods Totally 170 times of matched nasal swabs and sputum specimens of 78 COVID-19 patients in Shenzhen Third People's Hospital were collected from the same day. The samples were tested with real-time fluorescence PCR nucleic acid. The nasal swabs and sputum samples were analyzed and compared. Results A total of 78 patients were involved, including 33 males and 45 females. Age ranged 1-86 years old, the majority of young and middle-aged (20-<60 years, 59.0%) patients, followed by elderly patients (≥ 60 years, 33.0%), 4 children. Among 170 matched samples, 59 nasal swabs were positive, the positive rate was 34.7%; 79 sputum samples were positive, the positive rate was 46.5%, the difference was statistically significant ( P <0.01). There were 46 times of positive nasal swabs and sputum specimens simultaneously. The results showed that the Ct value of 27 sputum samples was lower than that of nasal swabs (58.7%), 17 sputum samples were higher than that of nasal swabs (37.0%), and 2 sputum samples were equal to that of nasal swabs (4.3%). This suggested a higher viral load in sputum specimens than in nose swabs. Conclusion In the nucleic acid assay of COVID-19 patients, the positive rate of sputum specimens is higher than that of nasal swabs, and the rate of missing detection is low. The viral load of sputum specimens is higher than that of nasal swabs, which is more conducive to the detection of viral nucleic acids, and patients are more receptive. 摘要：目的 分析新型冠状病毒肺炎(coranavims disease 2019, COVID-19)患者鼻拭子和痰标本病毒核酸检测结 果, 为临床采样方式的选择提供参考依据。 方法 收集深圳市第三人民医院新型冠状病毒肺炎78例患者共170例次 同一天鼻拭子与痰配对标本, 进行实时荧光PCR核酸检测, 分析比较鼻拭子和痰标本检测情况。 结果 78例患者中男 性33例, 女性45例, 年龄1∼86岁, 中青年(20∼<60岁) 患者居多 (占59.0%), 其次为老年(≥60岁) 患者 (占33.0%), 4例 为儿童。170例次配对标本中, 鼻拭子和痰标本核酸阳性的阳性率分别为34.7%(59/170)和46.5%(79/170), 差异有统 计学意义( P <0.01)。鼻拭子和痰标本同时阳性共46例次, 结果显示27例痰标本Ct值低于鼻拭子Ct值 (占58.7%), 17 例痰标本Ct值高于鼻拭子Ct值 (占37.0%), 2例痰标本Ct值等于鼻拭子Ct值 (占4.3%), 提示痰标本的病毒载量比鼻拭 子的病毒载量更高。 结论 在新型冠状病毒肺炎患者病毒核酸检测中, 痰标本的阳性率高于鼻拭子标本, 且漏检率低, 痰标本的病毒载量比鼻拭子的病毒载量更高, 更有利于病毒核酸的检出, 同时患者更易接受, 建议有痰患者优先采集 痰标本。