BACKGROUND: This study aimed to compare four anti-SARS-CoV-2 immunoassays in populations presenting different clinical severity levels .
METHODS: Three populations were included: `` severe-to-critical"ICU-hospitalized patients (n = 18), `` mild-to-moderate"hospitalized patients (n = 16) and non-hospitalized symptomatic patients (n = 24). Four commercial immunoassays were analyzed and validated: anti-IgG ARCHITECT® (Abbott), anti-Total antibodies (Ab) VITROS® (Ortho Clinical Diagnostics), anti-IgG NovaLisa® (NovaTec Immundiagnostica) and Healgen® IgM and IgG (Zhejiang Orient Gene Biotech). Sensitivities were evaluated according to days post-symptoms onset (pso). Specificities were evaluated on SARS-CoV-2-negative control sera collected before January 2020 .
RESULTS: A majority of severe-to-critically ill patients showed detectable Ab already at day 14 and sensitivities reached 100% after 22 days pso . For patients with``mild-to-moderate"illness, sensitivities increased by at least 5-fold from day 0 to day 14 pso . Non-hospitalized symptomatic individuals already seroconverted at day 14 days pso with 100% sensitivities for Total Ab VITROS® . Specificities were evaluated at 97% for ARCHITECT® and NovaLisa® , 98% for VITROS® and at 94% for Healgen® combined IgM and IgG . Five``severe-to-critically"ill patients presented high positive Ab levels for at least 16 weeks pso .
CONCLUSION: The Ab levels and the evaluated sensitivities, representing the true positive rate, increased overtime and were related to the COVID-19 severity . Automated Total Ab immunoassay showed better sensitivities and specificity for immunological surveillance and vaccine evaluation.