Analytical and clinical evaluation of four commercial SARS-CoV-2 serological immunoassays in hospitalized patients and ambulatory individuals

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-tomoderate" hospitalized patients (n = 16) and non-hospitalized symptomatic patients (n = 24). Four commercial immunoassays were analyzed and validated: anti-IgG ARCHITECT (R) (Abbott), anti-Total antibodies (Ab) VITROS (R) (Ortho Clinical Diagnostics), anti-IgG NovaLisa (R) (NovaTec Immundiagnostica) and Healgen (R) 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 (R). Specificities were evaluated at 97 % for ARCHITECT (R) and NovaLisa (R), 98 % for VITROS (R) and at 94 % for Healgen (R) 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.