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

• Published in: Clinical chemistry and laboratory medicine Vol. 59; no. 8; pp. 1444 - 1452
• Main Authors: Padoan, Andrea, Bonfante, Francesco, Cosma, Chiara, Di Chiara, Costanza, Sciacovelli, Laura, Pagliari, Matteo, Bortolami, Alessio, Costenaro, Paola, Musso, Giulia, Basso, Daniela, Giaquinto, Carlo, Plebani, Mario
• Format: Journal Article
• Language: English
• Published: Germany De Gruyter 27.07.2021; Walter De Gruyter & Company
• Subjects: Antibodies; Assaying; clinical performances; Coronaviruses; COVID-19; Evaluation; Immunoassays; Immunoglobulin G; Mathematical analysis; Neutralization; Neutralizing; Pandemics; plaque reduction neutralization test; SARS-CoV-2; Serology; Severe acute respiratory syndrome; Severe acute respiratory syndrome coronavirus 2; Viral diseases; SARS-CoV-2; neutralization; clinical performances; serology; plaque reduction neutralization test; immunoassays; antibodies
• ISSN: 1434-6621; 1437-4331; 1437-4331
• DOI: 10.1515/cclm-2021-0313

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 (PRNT ) Ab titers. A series of 546 samples were evaluated by SARS-CoV-2 RBD IgG assay (Snibe 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 PRNT test were available. An elevated correlation was obtained between the SARS-CoV-2 RBD IgG assay and the PRNT titer at univariate ( =0.689) and multivariate ( =0.712) analyses. SARS-CoV-2 S-RBD IgG assay shows satisfactory analytical and clinical performances, and a strong correlation with sera neutralizing activity.