Evaluation of the performance of SARS-CoV-2 antibody assays for the longitudinal population-based study of COVID-19 spread in St. Petersburg, Russia

Abstract

Background: An evident geographical variation in the SARS-CoV-2 spread requires seroprevalence studies based on local tests with robust validation against already available antibody tests and neutralization assays. This report summarizes the evaluation of antibody tests used in the representative population-based serological study of SARS-CoV-2 in Saint Petersburg, Russia. Methods: We used three different antibody tests throughout the study: chemiluminescent microparticle immunoassay (CMIA) Abbott Architect SARS-CoV-2 IgG, Enzyme-linked immunosorbent assay (ELISA) CoronaPass total antibodies test, and ELISA SARS-CoV-2-IgG-EIA-BEST. Clinical sensitivity was estimated with the SARS-CoV-2 PCR test as the gold standard and specificity in pre-pandemic sera samples using the cut-off recommended by manufacturers. Paired and unpaired serum sets were used. Measures of concordance were also calculated in the seroprevalence study sample against the microneutralization test (MNA). Findings: Sensitivity was equal to 91.1% (95% CI: 78.8-97.5) and 90% (95% CI: 76.4-96.4) for ELISA Coronapass and ELISA Vector-Best respectively. It was equal to 63.1% (95% CI (50.2-74.7) for CMIA Abbott. Specificity was equal to 100% for all the tests. Comparison of ROCs for three tests has shown lower AUC for CMIA Abbott, but not for ELISA Coronapass and CMIA Abbott. The cutoff SC/O ratio of 0.28 for CMIA-Abbott resulted in a sensitivity of 80% at the same full level of specificity. In less than one-third of the population-based study participants with positive antibody test results, we detected neutralizing antibodies in titers 1:80 and above. There was a moderate correlation between antibody assays results and MNA. Interpretation: Our validation study encourages the use of local antibody tests for population-based SARS-CoV-2 surveillance and sets the reference for the seroprevalence correction. Available tests are sensitive enough to detect antibodies in most individuals with previous positive PCR tests with a follow-up of more than 5 months. The Abbott Architect SARS-CoV-2 IgG s sensitivity can be significantly improved by incorporating a new cut-off. Relying on manufacturers test characteristics for correction of reported prevalence estimates may introduce bias to the study results.