Evaluations of serological test in the diagnosis of 2019 novel coronavirus (SARS-CoV-2) infections during the COVID-19 outbreak

Dachuan Lin; Lei Liu; Mingxia Zhang; Yunlong Hu; Qianting Yang; Jiubiao Guo; Youchao Dai; Yuzhong Xu; Yi Cai; Xinchun Chen; Kaisong Huang; Zheng Zhang

is the (which was not peer-reviewed) The copyright holder for this preprint . https: //doi.org/10.1101 //doi.org/10. /2020 using the same pure recombinant antigen and coupling condition (supplementary figure S1), the 206 detection specificity difference is more likely linked to intrinsic antibody traits and concentration 207 differences in the patients' blood. 208 We noted that four patients with clinical symptoms less than four days were simultaneously detected 209 by both IgM and IgG testing. A close examination of their medical record reveals that all of them had 210 previous contact with confirmed SARS-CoV-2 individuals in at least 16 days ago, pointing to the 211 possibility that they were probably asymptomatically infected by SARS-CoV-2 for certain time already. 212 Fourteen cases (17.7%) from 79 SARS-CoV-2 confirmed patients were not identified by our serological 213 testing method (both the IgM and IgG manner). Interestingly, of them, seven people were younger 214 than 8-year-old or over 70-year-old. These people generally have low immunity in which a clinical 215 symptom may occur rapidly upon exposure to the SARS-CoV-2, and we speculate that the antibodies 216 in these people may not develop well yet when testing. More investigations are warranted to 217 uncover the real situations. When comparing the detection rates in different age groups by our 218 method, we noted that a significantly lower detection rate in both lgM and lgG testing manner for the 219 individual group younger than 18 years old was observed compared to that of people aging from 18 to 220 65. An in-depth look at the days after onset for these 12 individuals younger than 18-years-old, the 221 symptom onset time for all the 12 people are less than 14 days with six people even less seven days 222 (Supplementary Table S2 ). The lower detection rate for these 12 people younger than 18-years-old 223 was likely associated with no or less production of antibodies in them yet when we collected the 224 serums.