Clinical validation of an immunochromatographic SARS‐Cov‐2 IgM/IgG antibody assay with Japanese cohort

Background The coronavirus disease 2019 (COVID‐19) has become a major health threat. To overcome COVID‐19, appropriate diagnosis methods are urgently needed. The aim of this study was to clinically evaluate the colloidal gold immunochromatography assay for SARS‐Cov‐2 IgM/IgG antibody (Ab). Methods Patients confirmed COVID‐19 (n = 51) were recruited prospectively from the Musashino Red Cross hospital and Tokyo Medical and Dental University Medical Hospital, between March and May 2020. And the analytical specificity was assessed with serum samples of patients without COVID‐19 (n = 100) collected between August to September 2019 before SARS‐CoV‐2 was first reported in China. Results Among COVID‐19 patients, a total of 87 serum samples were tested for SARS‐Cov‐2 IgM/IgG Ab assay. IgM was detected 71.0 %, 86.9 %, and 83.3 % at day8‐14, 15‐28, >29 after symptom onset and IgG was detected in 81.6 %, 87.0 %, and 94.4 %, respectively. The sensitivity of IgM and IgG Ab after day8 assay was significantly higher than before day7, respectively (p=0.0016, 0.0003). There were no positive results in 100 serum samples from patients without COVID‐19. Conclusion The SARS‐Cov‐2 IgM/IgG Ab assay had 79.7% / 86.1% sensitivity (the 8 days after from onset) and 100% specificity in this population. Highlights The colloidal gold immunochromatography assay for SARS‐Cov‐2 IgM/IgG antibody was evaluated with Japanese cohort. The serum samples were collected from the patients confirmed COVID‐19 (n = 51) and patients without COVID‐19 (n=100) admitted before SARS‐CoV2 was first reported in China (from August to September in 2019). The SARS‐Cov‐2 IgM/IgG Ab assay had 79.7% / 86.1% sensitivity (the 8 days after from onset) and 100% specificity.