Assessment and Comparison of Two Serological Approaches for the Surveillance of Health Workers Exposed to SARS-CoV-2

The aim of the present study was to assess the diagnostic performance of an LFA compared with an ELISA test in a cohort of HWs operating in a COVID-19 unit of a teaching hospital in southern Italy. We performed an observational, prospective, interventional study including 65 COVID-19 unit personnel. On a total of 196 serum samples (at least 2 serum samples for each HW), LFA and ELISA tests for SARS-COV-2 IgG and IgM were performed. Also, 32 serum samples of SARS-CoV-2 RNA positive patients at least 21 days before sampling, and 30 serum samples of patients obtained up to November 2019, before COVID-19 outbreak in China, were used as positive and negative controls, respectively. Of the 65 HWs enrolled, 6 were positive in LFA; overall, of the 196 serum samples, 20 were positive in LFA. All ELISA tests performed on serum samples collected from HWs were negative. The specificity of LFAs was 90.77% considering the 65 HWs and 89.80% considering all the 196 health workers serum samples analyzed. Considering the data on HWs, ELISA test for SARS-COV-2 antibodies showed a specificity of 100%, including all the 196 serum samples collected, and 100% including the 65 HWs. The ELISA and LFAs performed after 21 days last COVID-19 patient was discharged were all negative. LFAs compared to ELISA tests result in less specificity, considering COVID-19 negative personnel and patients. Thus, LFAs seem to be not adequate in the active surveillance of HWs.