Analytical and clinical performances of a SARS-CoV-2 S-RBD IgG assay: comparison with neutralization titers

Andrea Padoan, Francesco Bonfante, Chiara Cosma, Costanza Di Chiara, Laura Sciacovelli, Matteo Pagliari, Alessio Bortolami, Paola Costenaro, Giulia Musso, Daniela Basso, Carlo Giaquinto, Mario Plebani
2021 Clinical Chemistry and Laboratory Medicine  
SARS-CoV-2 serology presents an important role in several aspects of COVID-19 pandemic. Immunoassays performances have to be accurately evaluated and correlated with neutralizing antibodies. We investigated the analytical and clinical performances of a SARS-CoV-2 RBD IgG assay, automated on a high throughput platform, and the correlation of the antibodies (Ab) levels with the plaque reduction neutralization (PRNT50) Ab titers. A series of 546 samples were evaluated by SARS-CoV-2 RBD IgG assay
more » ... nibe diagnostics), including 171 negative and 168 positive SARS-CoV-2 subjects and a further group of 207 subjects of the COVID-19 family clusters follow-up cohort. Assay imprecision ranged from 3.98 to 12.18% being satisfactory at low and medium levels; linearity was excellent in all the measurement range. Considering specimens collected after 14 days post symptoms onset, overall sensitivity and specificity were 99.0 and 92.5%, respectively. A total of 281 leftover samples results of the PRNT50 test were available. An elevated correlation was obtained between the SARS-CoV-2 RBD IgG assay and the PRNT50 titer at univariate (ρ=0.689) and multivariate (ρ=0.712) analyses. SARS-CoV-2 S-RBD IgG assay shows satisfactory analytical and clinical performances, and a strong correlation with sera neutralizing activity.
doi:10.1515/cclm-2021-0313 pmid:33855843 fatcat:nimwvhlqlfcrpbs4np27rnj434