Performance assessment of 11 commercial serological tests for SARS-CoV-2 on hospitalized COVID-19 patients

Serre-Miranda, C.; Nobrega, C.; Roque, S.; Canto-Gomes, J.; Silva, C. S.; Vieira, N.; Barreira-Silva, P.; Alves-Peixoto, P.; Cotter, J.; Reis, A.; Formigo, M.; Sarmento, H.; Pires, O.; Carvalho, A.; Petrovykh, D. Y.; Dieguez, L.; Sousa, J. C.; Sousa, N.; Capela, C.; Palha, J. A.; Cunha, P. G.; Correia-Neves, M.

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 COVID-19 outbreak. Their thorough validation is of extreme importance before using them as epidemiological tools to infer population seroprevalence, and as complementary diagnostic tools to molecular approaches (e.g. RT-qPCR). Here we assayed commercial serological tests (semiquantitative and qualitative) from 11 suppliers in 126 samples collected from hospitalized COVID-19 patients, and from 36 healthy and HIV-infected individuals (collected at the pre-COVID-19 pandemic). Specificity was above 95% in 9 tests. Samples from COVID-19 patients were stratified by days since symptoms onset (<10, 10-15, 16-21 and >21 days). Tests sensitivity increases with time since symptoms onset, and peaks at 16-21 days for IgM and IgA (maximum: 91.2%); and from 16-21 to >21 days for IgG, depending on the test (maximum: 94.1%). Data from semiquantitative tests show that patients with severe clinical presentation have lower relative levels of IgM, IgA and IgG at <10 days since symptoms onset in comparison to patients with non-severe presentation. At >21 days since symptoms onset the relative levels of IgM and IgG (in one test) are significantly higher in patients with severe clinical presentation, suggesting a delay in the upsurge of Ig against SARS-CoV-2 in those patients. This study highlights the high specificity of most of the evaluated tests, and sensitivity heterogeneity. Considering the virus genetic evolution and population immune response to it, continuous monitoring of commercially available serological tests towards SARS-CoV-2 is necessary.