Background A few studies on antibody testing have focused on asymptomatic or mild
coronavirus disease 2019 MESHD (
COVID-19 MESHD) patients with low initial anti-severe acute
respiratory syndrome coronavirus 2 MESHD (SARS-CoV-2) antibody responses. Anti-SARS-CoV-2 antibody-testing performance was evaluated using blood samples from asymptomatic or mild
COVID-19 MESHD patients. Methods Blood samples were collected from 143
COVID-19 MESHD patients during an outbreak on a cruise ship 3 weeks after diagnosis. Simultaneously, a second SARS-CoV-2 genetic test was performed. Samples stored before the
COVID-19 pandemic MESHD were also used to evaluate the lateral flow immunochromatographic assay (LFA) and electrochemiluminescence immunoassay (ECLIA). Titers of anti-SARS-CoV-2 IgM and IgG antibodies against the nucleocapsid and
spike proteins PROTEIN were measured using the enzyme-linked immunosorbent assay to compare false-negative- with positive-result samples. Results Sensitivity, specificity, positive-predictive, and negative-predictive values of LFA-detected IgM antibodies were 0.231, 1.000, 1.000, and 0.613, respectively; those of LFA-detected IgG antibodies were 0.483, 0.989, 0.972, and 0.601, respectively; and those of ECLIA-detected total antibodies were 0.783, 1.000, 1.000, and 0.848, respectively. IgM-, IgG-, and total-antibody positivity rates in the patients with negative results from the second genetic testing were 22.9%, 47.6%, and 72.4%, respectively. All antibody titers, especially those of the IgG antibody against
nucleocapsid protein PROTEIN, were significantly lower in blood samples with false-negative results than in those with positive results. Conclusions These findings suggest that anti-SARS-CoV-2 antibody testing has lower performance in asymptomatic or mild
COVID-19 MESHD patients than required in the guidelines, and situations in which it is useful are limited.