SARS-CoV-2 Infection in Health Workers: Analysis from Verona SIEROEPID Study during the Pre-Vaccination Era.

BACKGROUND: To report the baseline phase of the SIEROEPID study on SARS-CoV-2 infection seroprevalence among health workers at the University Hospital of Verona, Italy, between spring and fall 2020; to compare performances of several laboratory tests for SARS-CoV-2 antibody detection. METHODS: 5299 voluntary health workers were enrolled from 28 April 2020 to 28 July 2020 to assess immunological response to SARS-CoV-2 infection throughout IgM, IgG and IgA serum levels titration by four laboratory tests. Association of antibody titre with several demographic variables, swab tests and performance tests (sensitivity, specificity, and agreement) were statistically analyzed. RESULTS: The overall seroprevalence was 6%, considering either IgG and IgM, and 4.8% considering IgG. Working in COVID-19 Units was not associated with a statistically significant increase in the number of infected workers. Cohen's kappa of agreement between MaglumiTM and VivaDiagTM was quite good when considering IgG only (Cohen's kappa = 78.1%, 95% CI 74.0-82.0%), but was lower considering IgM (Cohen's kappa = 13.3%, 95% CI 7.8-18.7%). CONCLUSION: The large sample size with high participation (84.7%), the biobank and the longitudinal design were significant achievements, offering a baseline dataset as the benchmark for risk assessment, health surveillance and management of SARS-CoV-2 infection for the hospital workforce, especially considering the ongoing vaccination campaign. Study results support the national regulator guidelines on using swabs for SARS-CoV-2 screening with health workers and using the serological tests to contribute to the epidemiological assessment of the spread of the virus.

Evaluation of three immunochromatographic tests in COVID-19 serologic diagnosis and their clinical usefulness.

Results of three rapid immunochromatographic tests (ICTs) were compared with those obtained with two automated immunoassays for evaluation of their usefulness. One hundred fifty-nine patients and 67 healthy volunteers were included. Different assays demonstrate 41-45% of diagnostic sensitivities and 91-98% of specificities, with substantial agreement (89.3-91.2%), but a high percentage of weak positive results (13-22%) was observed with ICTs. ICTs performances were comparable to those of automated immunoassays. ICTs could have a role as screening approach due to their easy usability. Subjective interpretation, significant rate of uncertain results, uncertainty on viral antigens source are undoubtedly drawbacks.