COVID-19 diagnosis and study of serum SARS-CoV-2 specific IgA, IgM and IgG by a quantitative and sensitive immunoassay

Huan Ma; Weihong Zeng; Hongliang He; Dan Zhao; Yunru Yang; Dehua Jiang; Peigen Zhou; Yingjie Qi; Weihuang He; Changcheng Zhao; Ruting Yi; Xiaofang Wang; Bo Wang; Yuanhong Xu; Yun Yang; Arnaud John Kombe Kombe; Chengchao Ding; Jiajia Xie; Yong Gao; Linzhao Cheng; Yajuan Li; Xiaoling Ma; Tengchuan Jin

Highly purified SARS-CoV-2 NP and RBD proteins (supplementary figure 1) were employed to 222 develop a series of serological test kits, to detect the presence of NP-and RBD-specific IgA, IgM, and 223 IgG, respectively (hereinafter referred to as "NP kit" and "RBD kit"). A cohort of 216 sera from 87 224 SARS-CoV-2 infected patients was tested with both NP and RBD kits, together with 20 sera from 20 225 non-SARS-CoV-2 infected patients as negative controls initially. The NP kits for IgA, IgM, and IgG 226 showed diagnostic sensitivities of 89· 8%, 78· 2%, and 95· 8%, and specificities of 85· 0%, 95· 0%, and 227 100% respectively (supplementary figure 2A-C). However, the RBD kits for detecting IgA, IgM, and 228 IgG showed higher diagnostic sensitivities of 97· 2%, 93· 1%, and 96· 8%, and specificities of 100%, 229 90· 0%, and 100%, respectively (supplementary figure 2D-F). We conclude that the RBD based kits IgG kits, the sensitivity, specificity and overall agreement elevate to 99· 1%, 100%, and 99· 7%, 243 respectively. This is much better than when IgM and IgG were combined. When IgA, IgM, or IgG 244 individual kit was used, we observed a total of 9 (0.61% to 6.67%), 37 (5.54% to 40.0%), and 1 (0 to CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.