LAUSR

Background Commercial availability of serological tests to evaluate immunoglobulins (Ig) towards severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has grown exponentially since the onset of disease outbreak. Their thorough validation is of extreme importance before using them as epidemiological tools to infer seroprevalence in specific populations, and as complementary diagnostic tools to molecular approaches (e.g. RT- qPCR). Methods Commercial serological tests from 11 suppliers were assayed side-by-side using 126 samples from SARS-CoV-2-infected inpatients, and 36 healthy and HIV-infected individuals. Results Most of the tests assayed have >95% specificity. For sensitivity calculation, samples were stratified by days since symptoms onset; sensitivity peaks at 16-21 days for IgM and IgA (maximum: 91.2%; Euroimmun); and, varying with the test, at 16-21 or at >21 days for IgG (maximum: 94.1%; Snibe). Data from semiquantitative tests show that patients with severe clinical outcome, in comparison with patients with a non-severe presentation, reveal lower levels of Ig against SARS-CoV-2 at <10 days since symptoms onset, and higher levels at >21 days. Conclusions This study highlights the sensitivity heterogeneity accompanied by an almost general high specificity of most tests and sets the basis for the usefulness of these tests as a complement for diagnosis and population seroprevalence studies.