Dynamic changes of RNA and antibodies in SARS-CoV-2 infected patients remain largely unknown, and influence factors for antibody production have not been fully clarified. In this study, consecutive throat swabs specimens (n = 1875) from 187 patients were collected to analyse the dynamic changes of RNA. Moreover, 162 serial serum samples from 31 patients were tested for seroconversion of IgM and IgG. Meanwhile, IgM and IgG were also detected in 409 COVID-19 patients and 389 controls. Additionally, the logistic regression analysis was executed to identify the possible influence factors for antibody production. The median positive conversion time for RNA was day 7 (IQR, 3–11), and the positive rate was highest in day 1–5 (74.59 %) and then gradually decreased. The median time of seroconversion for IgM and IgG were both day 12 (IQR, 10–15). The sensitivity and specificity for IgM (or IgG) was 87.04% and 96.92%, respectively. Multivariate logistic regression indicated that reduced lymphocytes and short positive conversion time for SARS-CoV-2 RNA were independent factors for negative results of IgM and IgG. In conclusion, RNA and antibodies should be combined for COVID-19 diagnosis, and delayed seroconversion was influenced by the decreased lymphocytes and short positive conversion time for RNA.

在SARS-CoV-2感染患者中，RNA和抗体的动态变化仍是未知之数，并且尚未充分阐明抗体产生的影响因素。在这项研究中，连续的咽拭子标本（n = 1875）从187名患者中收集来分析RNA的动态变化。此外，测试了来自31位患者的162个系列血清样品的IgM和IgG的血清转化。同时，在409例COVID-19患者和389例对照中还检测到IgM和IgG。另外，进行逻辑回归分析以鉴定抗体产生的可能影响因素。RNA的中位阳性转化时间为第7天（IQR，3-11），阳性率在1-5天达到最高（74.59％），然后逐渐下降。IgM和IgG血清转换的中位时间均为第12天（IQR，10-15）。IgM（或IgG）的敏感性和特异性分别为87.04％和96.92％。多因素logistic回归表明，SARS-CoV-2 RNA的淋巴细胞减少和阳性转化时间短是IgM和IgG阴性结果的独立因素。总之，RNA和抗体应结合用于COVID-19诊断，并且血清减少和淋巴细胞的减少以及RNA阳性转化时间短会影响血清转换。