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. 2021 Apr 14;59(8):1444-1452.
doi: 10.1515/cclm-2021-0313. Print 2021 Jul 27.

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

Andrea Padoan  1   2 , Francesco Bonfante  3 , Chiara Cosma  2 , Costanza Di Chiara  4 , Laura Sciacovelli  2 , Matteo Pagliari  3 , Alessio Bortolami  3 , Paola Costenaro  4 , Giulia Musso  2 , Daniela Basso  1   2 , Carlo Giaquinto  4 , Mario Plebani  1   2
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Free article

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

Andrea Padoan et al. Clin Chem Lab Med. .
Free article

Abstract

Objectives: 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.

Methods: 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.

Results: 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.

Conclusions: SARS-CoV-2 S-RBD IgG assay shows satisfactory analytical and clinical performances, and a strong correlation with sera neutralizing activity.

Keywords: SARS-CoV-2; antibodies; clinical performances; immunoassays; neutralization; plaque reduction neutralization test; serology.

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