BACKGROUND Coronavirus disease 2019 (COVID-19) has become a public health emergency. The widely used reverse transcription PCR (RT-PCR) method has limitations for clinical diagnosis and treatment. METHODS A total of 323 samples from 76 COVID-19 confirmed patients were analyzed by droplet digital PCR (ddPCR) and RT-PCR based two target genes (ORF1ab and N). Nasal swabs, throat swabs, sputum, blood, and urine were collected. Clinical and imaging data were obtained for clinical staging. RESULTS In 95 samples tested positive by both methods, the cycle threshold (Ct) of RT-PCR was highly correlated with the copy numbed of ddPCR (ORF1ab gene, R2 = 0.83; N gene, R2 = 0.87). 4 (4/161) negative and 41 (41/67) single-gene positive samples tested by RT-PCR were positive according to ddPCR with viral load ranging from 11.1 to 123.2 copies/test. Then the viral load of respiratory samples was compared and the average viral load in sputum (17429 ± 6920 copies/test) was found to be significantly higher than in throat swabs (2552 ± 1965 copies/test, p < 0.001) and nasal swabs (651 ± 501 copies/test, p < 0.001). Furthermore, the viral load in the early and progressive stages were significantly higher than that in the recovery stage (46800 ± 17272 vs 1252 ± 1027, p < 0.001) analyzed by sputum samples. CONCLUSIONS Quantitative monitoring of viral load in lower respiratory tract samples helps to evaluate disease progression, especially in cases of low viral load.

中文翻译：

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感染患者中SARS-CoV-2的定量检测和病毒载量分析。

背景冠状病毒病2019（COVID-19）已成为公共卫生突发事件。广泛使用的逆转录PCR（RT-PCR）方法在临床诊断和治疗方面存在局限性。方法采用液滴数字PCR（ddPCR）和基于两个靶基因（ORF1ab和N）的RT-PCR对来自COVID-19确诊患者的323份样本进行分析。收集鼻拭子，咽喉拭子，痰液，血液和尿液。获得临床和影像学数据用于临床分期。结果在两种方法均检测为阳性的95个样品中，RT-PCR的循环阈值（Ct）与ddPCR的拷贝数高度相关（ORF1ab基因，R2 = 0.83； N基因，R2 = 0.87）。根据ddPCR，通过RT-PCR测试的4（4/161）阴性和41（41/67）单基因阳性样品为阳性，病毒载量为11.1至123.2拷贝/测试。然后比较呼吸道样本的病毒载量，发现痰中的平均病毒载量（17429±6920拷贝/测试）显着高于喉拭子（2552±1965拷贝/测试，p <0.001）和鼻拭子（ 651±501份/测试，p <0.001）。此外，通过痰标本分析，早期和进展阶段的病毒载量显着高于恢复阶段的病毒载量（46800±17272与1252±1027，p <0.001）。结论定量监测下呼吸道样本中的病毒载量有助于评估疾病进展，尤其是在病毒载量低的情况下。001）和鼻拭子（651±501份/测试，p <0.001）。此外，通过痰标本分析，早期和进展阶段的病毒载量显着高于恢复阶段的病毒载量（46800±17272与1252±1027，p <0.001）。结论定量监测下呼吸道样本中的病毒载量有助于评估疾病进展，尤其是在病毒载量低的情况下。001）和鼻拭子（651±501份/测试，p <0.001）。此外，通过痰标本分析，早期和进展阶段的病毒载量显着高于恢复阶段的病毒载量（46800±17272与1252±1027，p <0.001）。结论定量监测下呼吸道样本中的病毒载量有助于评估疾病进展，尤其是在病毒载量低的情况下。