Chiereghin A., Zagari R. M., Galli S., Moroni A., Gabrielli L., Venturoli S., Bon I., Rossini G., Saracino I. M., Pavoni M., Lafratta S., Deni A., Felici S., Borghi M., Guerra L., Raumer L., Lodi V., Viale P., Attard L., Lazzarotto T., Borgatti E. C., Leone M., Mancini R., Petrisli E., Turello G., Gaibani P., Vocale C., Roncarati G., Magnani S., Fioro M. A., Fava M., Marzaduri A., Di Felice G., Caveduri F., Chiereghin A., Zagari R.M., Galli S., Moroni A., Gabrielli L., Venturoli S., Bon I., Rossini G., Saracino I.M., Pavoni M., Lafratta S., Deni A., Felici S., Borghi M., Guerra L., Raumer L., Lodi V., Viale P., Attard L., Lazzarotto T., Borgatti E.C., Leone M., Mancini R., Petrisli E., Turello G., Gaibani P., Vocale C., Roncarati G., Magnani S., Fioro M.A., Fava M., Marzaduri A., Di Felice G., and Caveduri F.
Introduction: Few data on the diagnostic performance of serological tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are currently available. We evaluated sensitivity and specificity of five different widely used commercial serological assays for the detection of SARS-CoV-2–specific IgG, IgM, and IgA antibodies using reverse transcriptase-PCR assay in nasopharyngeal swab as reference standard test.Methods: A total of 337 plasma samples collected in the period April–June 2020 from SARS-CoV-2 RT-PCR positive (n = 207) and negative (n = 130) subjects were investigated by one point-of-care lateral flow immunochromatographic assay (LFIA IgG and IgM, Technogenetics) and four fully automated assays: two chemiluminescence immunoassays (CLIA-iFlash IgG and IgM, Shenzhen YHLO Biotech and CLIA-LIAISON® XL IgG, DiaSorin), one electrochemiluminescence immunoassay (ECLIA-Elecsys® total predominant IgG, Roche), and one enzyme-linked immunosorbent assay (ELISA IgA, Euroimmune).Results: The overall sensitivity of all IgG serological assays was >80% and the specificity was >97%. The sensitivity of IgG assays was lower within 2 weeks from the onset of symptoms ranging from 70.8 to 80%. The LFIA and CLIA-iFlash IgM showed an overall low sensitivity of 47.6 and 54.6%, while the specificity was 98.5 and 96.2%, respectively. The ELISA IgA yielded a sensitivity of 84.3% and specificity of 81.7%. However, the ELISA IgA result was indeterminate in 11.7% of cases.Conclusions: IgG serological assays seem to be a reliable tool for the retrospective diagnosis of SARS-CoV-2 infection. IgM assays seem to have a low sensitivity and IgA assay is limited by a substantial rate of indeterminate results.