The real life performance of 7 automated anti-SARS-CoV-2 IgG and IgM/IgA immunoassays

OBJECTIVES: This study was aimed at providing some insights into the real-life performance of the commercial, clinically validated anti-SARS-CoV-2 antibody assays. METHODS: The residual, anonymized samples from 97 patients referred for anti-SARS-CoV-2 antibodies testing were included in the study. The initial assessment was performed with the Euroimmun ELISAs, followed by the assays provided by: NovaTec, Snibe, Vircell, Roche, Abbott and DiaSorin. The analyses of the results were performed separately for the antibodies of the early (IgM/IgA) and late (IgG) immune response. RESULTS: We observed a high variability of the results obtained with the investigated immunoassays. The fully concordant results were reported for only 57 out of 97 samples tested for IgG antibodies and for 34 out of 97 samples for IgM/IgA. The highest percentage of positive results was noted for the Euroimmun and Vircell ELISAs and the lowest for Novatec ELISAs. We proposed to distinguish true and false positive results based on the sum of positive results obtained with different methods. We arbitrarily considered reference positive samples reactive in at least half of the assays. The assay that proved to correlate the best with those reference results was the Roche electrochemiluminescence immunoassay. CONCLUSIONS: The differences observed between immunoassays targeting the early phase antibodies were much more pronounced than between IgG assays, suggesting their lower value for clinical use. Our study also showed a high percentage of plausibly false (positive or negative) results obtained with ELISAs, which suggests their inferiority to the automated immunoassays.