Objective

Low viral load from patients infected with SARS-CoV-2 during infection late stage easily lead to false negative nucleic acid testing results, thus having great challenges to the prevention and control of the current pandemic. In present study, we mainly aimed to evaluate specimen types and specimen collection timepoint on the positive detection of 2019 novel coronavirus from patients at infection late stage based on RT-PCR testing.

Methods

Paired nasopharyngeal swabs, nasal swabs, oropharyngeal swabs and anal swabs were collected from patients infected with SARS-CoV-2 during infection late stage before washing in the morning and afternoon on the same day. Then virus RNA was extracted and tested for 2019-nCoV identification by RT-PCR within 24 h.

Results

Viral load was low at late infection stage. Specimens collected before washing in the morning would increase the detection ratio of 2019-nCoV. Detection ratio of nasopharyngeal swab [65 (95 % CI: 49.51–77.87) vs 42.5(95 % CI: 28.51–57.8)] or nasal swab [57.5 (95 % CI: 42.2–71.49) vs 35 (95 % CI: 22.13–50.49)] is higher not only than oropharyngeal swab[22.5 (95 % CI: 12.32–37.5) vs 7.5 (95 % CI: 2.58–19.86)], but also anal swab[2.5 (95 % CI: 0.44–12.88) vs 5 (95 % CI: 1.38–16.5)].

Conclusions

In summary, our research discovers that nasopharyngeal or nasal swab collected before washing in the morning might be more suitable for detecting of large-scale specimens from patients infected with low SARS-CoV-2 load during infection late stage. Those results could facilitate other laboratories in collecting appropriate specimens for improving detection of SARS-CoV-2 from patients during infection late stage as well as initially screening.

中文翻译：

---

拭子类型和收集时间对使用RT-PCR分析检测SARS-COV-2的价值。

目的

在感染后期，来自感染SARS-CoV-2的患者的病毒载量低，很容易导致假阴性核酸检测结果，从而对当前大流行的预防和控制提出了巨大挑战。在本研究中，我们的主要目的是基于RT-PCR测试，从感染后期的患者中阳性检测2019年新型冠状病毒，以评估标本类型和标本采集时间。

方法

从感染后期感染SARS-CoV-2的患者中收集成对的鼻咽拭子，鼻拭子，口咽拭子和肛门拭子，然后在当天上午和下午进行清洗。然后提取病毒RNA，并在24小时内通过RT-PCR测试2019-nCoV鉴定。

结果

感染后期病毒载量低。早晨清洗前收集的标本会增加2019-nCoV的检出率。鼻咽拭子[65（95％CI：49.51–77.87）vs 42.5（95％CI：28.51–57.8）]或鼻拭子[57.5（95％CI：42.2–71.49）vs 35（95％CI：22.13）的检出率–50.49）]不仅高于口咽拭子[22.5（95％CI：12.32–37.5）vs 7.5（95％CI：2.58–19.86）]，而且也高于肛门拭子[2.5（95％CI：0.44–12.88） vs 5（95％CI：1.38–16.5）]。

结论

总而言之，我们的研究发现，早上清洗之前收集的鼻咽或鼻拭子可能更适合于在感染后期检测低SARS-CoV-2感染患者的大规模标本。这些结果可能有助于其他实验室收集合适的标本，以改善感染后期以及最初筛查期间患者的SARS-CoV-2检测。