SARS-CoV-2 seroprevalence in hospital employees in Italy

The SARS-CoV-2 outbreak early in 2020 overwhelmed the Italian national health system, and hospitals were considered places at high risk of spreading the infection We explored specific antibody seroprevalence of all employees at a single hospital in the epicenter of the outbreak, to identify risky pathways and to evaluate the usefulness of antibody testing Methods: All hospital workers were invited to fill in a questionnaire and undergo a blood test for SARS-CoV-2 IgG, using two commercial tests (DiaSorin and Abbott) The SARSCoV-2 S1/S2 IgG test (DiaSorin, Saluggia, Italy) is a chemiluminescence immunoassay for quantifying antispike 1 (S1) and anti-spike 2 (S2) IgG on the LIAISON XL automated analyzer;according to the manufacturer, a titer 15 is positive;values below 3 8 are undetectable The SARS-CoV-2 IgG assay (Abbott, Abbott Park, Illinois, USA) is a chemiluminescent microparticle immunoassay for quantifying anti-capsid IgG on the ARCHITECT i System analyzer;according to the manufacturer, a titer 1 4 is positive Subjects who tested positive for SARS-CoV-2 IgG underwent a confirmatory nasopharyngeal swab PCR test Seropositivity was determined overall and according to demographic and occupations characteristics, for both tests singly and combined Results: The study enrolled 1562 hospital workers Overall, 153 participants (9 8%) were positive for SARS-CoV-2 IgG on DiaSorin test, and 150 (9 6%) were positive on Abbott test;both tests were positive in 123 cases (7 9%) and at least one was positive in 180 cases (11 5%) Factors associated with SARSCoV-2 seropositivity included: Being a smoker, working in Emergency or Medicine Departments, self-reporting a relative with COVID-19 or symptoms suggestive of COVID-19 Conclusion: Seroprevalence for SARS-CoV-2 in this population of hospital workers was overall about 10%, with an excess prevalence in roles and departments associated with contacts with COVID-19 patients