Comparison between rapid and laboratory serological tests in the context of the first responders during the SARS-CoV-2 outbreak: are the two tests interchangeable?

The SARS-CoV-2 virus appeared and was discovered in the year 2019, marking its significance. The spread of the virus also had serious consequences for national safety; members of the Police and Fire Brigade contracted the infection and therefore the efficiency of their operational activity decreased. Since the beginning of 2020, the biological laboratory of the Chemical Biological Radiological Nuclear (CBRN) unit of Milan's Fire Brigade headquarters performed thousands of serological tests to monitor the health of the Fire Brigade and various branches of the Police Forces. The aim of this study is to evaluate the degree of concordance and interchangeability between a lateral flow immunochromatographic assay (LFIA) and an automated laboratory immunoassay with different viral targets by comparing the data gathered from a sample group of firemen and policemen participating in a serological screening campaign. The serological tests used in this study are the LYHER® Novel Coronavirus (2019-nCoV) IgM/IgG Antibody Combo Test Kit and the Elecsys® Anti-SARS-CoV-2. The degree of concordance was computed using Cohen's kappa, with a result of 0.78 (CI 95%, 0.661-0.898), which is equivalent to a substantial agreement measured between the two tests. Additionally, the sensitivity of both serological tests was found to be 97%.