Reliability of serological tests for COVID-19: Comparison of three immunochromatography test kits for SARS-CoV-2 antibodies

Fujigaki, Hidetsugu; Takemura, Masao; Osawa, Michiko; Sakurai, Aki; Nakamoto, Kentaro; Seto, Koichi; Fujita, Takashi; Hata, Tadayoshi; Akiyama, Hidehiko; Doi, Yohei; Saito, Kuniaki

Background: Several immunochromatographic serological test kits have been developed to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific antibodies, but their relative performance and potential clinical utility is unclear. Methods: Three commercially available serological test kits were evaluated using 99 serum samples collected from 29 patients diagnosed with coronavirus disease 2019 (COVID-19). Results: The IgM antibody-positive rates of the three serological test kits for samples taken at the early stage of the disease (0-6 days after onset) were 19.0%, 23.8%, and 19.0%, respectively. The IgM antibody-positive rates over the entire period were 21.2%, 60.6%, and 15.2%, respectively. The IgG antibody-positive rates for samples taken after 13 days of onset were 100.0%, 97.6%, and 97.6%, respectively. Conclusion: There were large differences among the results of the three test kits. Only few cases showed positive results for IgM in the early stage of disease and the IgM antibody-positive rates over the entire period were low, suggesting that the kits used in this study were unsuitable for diagnosis of COVID-19. The IgG antibody was positive in almost all samples after 13 days of onset, suggesting that it may be useful for determining infections in the recent past.