Covid-19 serology in nephrology health care workers

Background: Chronic kidney disease patients show a high mortality in case of a SARS-CoV-2 infection. Thus, to be informed on Nephrology personnel9s sero-status might be crucial for patient protection. However, limited information exists about the presence of SARS-CoV-2 antibodies in asymptomatic individuals. Methods: We examined the seroprevalence of SARS-CoV-2 IgG and IgM antibodies among health care workers of a tertiary care kidney center during the peak phase of the Covid-19 crisis in Austria using an orthogonal test strategy and a total of 12 commercial nucleocapsid protein or spike glycoprotein based assays as well as Western blotting and a neutralization assay. Results: At baseline 60 of 235 study participants (25.5%, 95% CI: 20.4-31.5) were judged to be borderline positive or positive for IgM or IgG using a high sensitivity/low specificity threshold in one test system. Follow-up analysis after about two weeks revealed IgG positivity in 12 (5.1%, 95% CI: 2.9-8.8) and IgM positivity in six (2.6%, 95% CI: 1.1-5.6) in at least one assay. 2.1% (95% CI: 0.8-5.0) of health care workers showed IgG nucleocapsid antibodies in at least two assays. By contrast, positive controls with proven Covid-19 showed antibody positivity among almost all test systems. Moreover, serum samples obtained from health care workers did not show SARS-CoV-2 neutralizing capacity, in contrast to positive controls. Conclusions: Using a broad spectrum of antibody tests the present study revealed inconsistent results for SARS-CoV-2 seroprevalence among asymptomatic individuals, while this was not the case among Covid-19 patients.