BACKGROUND The novel coronavirus SARS-CoV-2 is a newly emerging virus. The antibody response in infected patient remains largely unknown, and the clinical values of antibody testing have not been fully demonstrated. METHODS A total of 173 patients with SARS-CoV-2 infection were enrolled. Their serial plasma samples (n=535) collected during the hospitalization were tested for total antibodies (Ab), IgM and IgG against SARS-CoV-2. The dynamics of antibodies with the disease progress was analyzed. RESULTS Among 173 patients, the seroconversion rate for Ab, IgM and IgG was 93.1%, 82.7% and 64.7%, respectively. The reason for the negative antibody findings in 12 patients might due to the lack of blood samples at the later stage of illness. The median seroconversion time for Ab, IgM and then IgG were day-11, day-12 and day-14, separately. The presence of antibodies was <40% among patients within 1-week since onset, and rapidly increased to 100.0% (Ab), 94.3% (IgM) and 79.8% (IgG) since day-15 after onset. In contrast, RNA detectability decreased from 66.7% (58/87) in samples collected before day-7 to 45.5% (25/55) during day 15-39. Combining RNA and antibody detections significantly improved the sensitivity of pathogenic diagnosis for COVID-19 (p<0.001), even in early phase of 1-week since onset (p=0.007). Moreover, a higher titer of Ab was independently associated with a worse clinical classification (p=0.006). CONCLUSIONS The antibody detection offers vital clinical information during the course of SARS-CoV-2 infection. The findings provide strong empirical support for the routine application of serological testing in the diagnosis and management of COVID-19 patients.

中文翻译：

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新型冠状病毒病患者对SARS-CoV-2的抗体应答2019。

背景技术新型冠状病毒SARS-CoV-2是一种新兴的病毒。感染患者中的抗体反应仍然未知，并且抗体测试的临床价值尚未得到充分证明。方法纳入173例SARS-CoV-2感染患者。对他们在住院期间收集的系列血浆样品（n = 535）进行了抗SARS-CoV-2总抗体（Ab），IgM和IgG检测。分析了抗体随疾病进展的动态。结果在173例患者中，Ab，IgM和IgG的血清转化率分别为93.1％，82.7％和64.7％。12例患者抗体阴性的原因可能是由于疾病后期缺乏血液样本。Ab，IgM和IgG的中值血清转化时间分别为第11天，12天和14天。发病后1周内患者中抗体的存在率<40％，并且自发病后第15天起迅速增加至100.0％（Ab），94.3％（IgM）和79.8％（IgG）。相反，RNA的可检测性从第7天之前收集的样品中的66.7％（58/87）降低到15-39天期间的45.5％（25/55）。结合RNA和抗体检测可显着提高COVID-19病原学诊断的敏感性（p <0.001），即使在发病后1周的早期（p = 0.007）。此外，较高的Ab滴度独立地与较差的临床分类相关（p = 0.006）。结论在SARS-CoV-2感染过程中，抗体检测可提供重要的临床信息。这些发现为血清学检测在COVID-19患者的诊断和治疗中的常规应用提供了有力的经验支持。