Correlation of two Elisa Assay in detection of anti SARS-CoV-2 antibody

Background. In this study SARS-CoV-2 serology was investigated, using two different ELISA assay, in a cohort of subjects convalescing after COVID-19 recruited for the establishment of a hyperimmune plasma bank. Methods. SARS-CoV-2 serology was investigated in 326 subjects using two commercial ELISA methods: CLIA, MAGLUMI 2019-nCoV IgG CLIA and DiaSorin LIAISON SARS-CoV-2 S1/S2 IgG. Results. Using the MAGLUMI IgG assay 56 subjects 17% were negative and using the SORIN IgG assay 43 subjects (13%) were negative too. MAGLUMI IgG test and the SORIN IgG test showed an good agreement (Cohen's K index = 0.65). Conclusions. Among 326 subjects evaluated after a microbiologically confirmed symptomatic COVID-19 disease in a not negligible number of subject was impossible to demonstrate a humoral immune response In our experience, the MAGLUMI and SORIN tests have shown good agreement in identifying subjects with IgG antibodies to SARS-CoV-2. However, the quantitative response appears to be very little comparable. Moreover results obtained in this study further underline the need for an evaluation of the pre-analytical, analytical conditions and post-analytical and the need for better standardization and harmonization of diagnostic serological tests for SARS-CoV-2.