SARS-CoV-2 seroepidemiological study in healthcare workers and discordant results using seven different diagnostic methods

The aim of the study was to access the SARS-CoV-2 antibody seroprevalence in healthcare workers (HCWs) of a tertiary pediatric hospital after the first wave of the pandemic and to compare the results among seven commercially available antibody detection assays, including chemiluminescence (CMIA), electroluminescence (ECLIA), Εnzyme-Linked Immunosorbent Assay (ELISA), and rapid immunochromatography (RIC). SARS-CoV-2 antibody detection was performed in serum samples of 1216 HCWs, using a reference CMIA assay and 8/1216 (0.66%) were detected positive. Positive serum samples were further tested with other assays; however, only one sample was positive by all tests. The rest 7 cases were negative with ECLIA and ELISA and gave discordant results with RIC test. Six months later, new serum samples of seropositive HCWs were analyzed with the same 7 tests, with inconsistent results again. Identification of reliable SARS-CoV-2 antibody tests is important to determine the actual number of past infections, the duration of antibodies, and guide public health decisions.