Diagnostic value and dynamic variance of serum antibody in coronavirus disease 2019

Abstract Objective To investigate the diagnostic value of serological test and dynamitic variance of serum antibody in coronavirus disease 2019 (COVID-19). Methods We retrospectively included 43 patients with a laboratory-confirmed infection and 33 patients with suspected infection who were finally excluded. The IgM/IgG titer of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was measured by chemiluminescence immunoassay analysis. Results Compared to molecular detection, the sensitivity of serum IgM and IgG antibodies to diagnose COVID-19 were 48.1% and 88.9%, and the specificity were 100% and 90.9%, respectively. In COVID-19 group, IgM positive rate almost increased first then decreased over time, however, IgG positive rate increased till 100% and was higher than IgM all the time. IgM positive rate and titer were not significantly different before and after viral negative. IgG positive rate was up to 90% and not significantly different before and after viral negative. However, the median titer of IgG after viral negative was twice than that before with significant difference. Conclusion Viral serological test is an effective diagnostic means for SARS-CoV-2 infection. The positive rate and titer variance of IgG are higher than that of IgM in COVID-19.