Evaluation of the performance of SARS‐­CoV­‐2 antibody assays for a longitudinal population­based study of COVID‐­19 spread in St. Petersburg, Russia

Abstract

Geographical variation in severe acute respiratory syndrome coronavirus 2 (SARS­‐CoV­‐2) spread requires seroprevalence studies based on local tests, but robust validation is needed. We summarize an evaluation of antibody tests used in a serological study of SARS‐­CoV­‐2 in Saint Petersburg, Russia. We validated three different antibody assays: chemiluminescent microparticle immunoassay (CMIA) Abbott Architect SARS‐­CoV­‐2 immunoglobulin G (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 polymerase chain reaction (PCR) test as the gold standard using manufacturer recommended cutoff. Specificity was estimated using pre­pandemic sera samples. The median time between positive PCR test results and antibody tests was 21 weeks. Measures of concordance were calculated against the microneutralization test (MNA).Sensitivity was equal to 91.1% (95% confidence intervbal [CI]: 78.8–97.5), 90% (95% CI: 76.4–96.4), and 63.1% (95% CI [50.2–74.7]) for ELISA Coronapass, ELISA Vector­Best, and CMIA Abbott, respectively. Specificity was equal to 100% for all the tests. Comparison of receiver operating characteristics has shown lower AUC for CMIA Abbott. The cut­off SC/O ratio of 0.28 for CMIA Abbott resulted in a sensitivity of 80% at the same level of specificity. Less than 33% of the participants with positive antibody test results had neutralizing antibodies in titers 1:80 and above. Antibody assays results and MNA correlated moderately. This study encourages the use of local antibody tests and sets the reference for seroprevalence correction. Available tests' sensitivity allows detecting antibodies within the majority of PCR­ positive individuals. The Abbott assay sensitivity can be improved by incorporating a new cut­off. Manufacturers' test characteristics may introduce bias into the study results.

Decline of Anti-SARS-CoV-2 IgG Antibody Levels 6 Months after Complete BNT162b2 Vaccination in Healthcare Workers to Levels Observed Following the First Vaccine Dose

“…One dose of vaccine received after COVID-19 is sufficient to produce peak antibody levels extremely quickly. These findings agree with the results of previous studies and go in line with the recommendation of second dose administration 6 months after recovering from COVID-19 [14][15][16][17][18][19][20][21][22][23][24][25][27][28][29][30]. Furthermore, these results can be explained by the limited humoral response to SARS-CoV-2 and the self-maintenance nature of the immune system.…”

“…Since BNT162b2 vaccine is based on the recombinant S antigen, NP-specific antibodies are of great help in the retrospective diagnosis of COVID-19. However, a common pitfall of this approach is a relatively quick decay of NP-specific antibodies after disease onset [2,3,[7][8][9][10]21,24,25,34]. Although we expect that the vast majority of participants with a history of COVID-19 were correctly identified, asymptomatic cases may have been missed.…”

“…Post-COVID-19 specific antibodies are directed toward different antigens, such as the nucleoprotein (NP) and spike (S) antigens. Considering that mRNA vaccines are based on the S1 subunit of the recombinant S antigen, post-vaccination assessment of immunity is only feasible with S1-specific serological tests [19,[21][22][23][24][25].…”

Seropositivity of SARS-CoV-2 in the Population of Kazakhstan: A Nationwide Laboratory-Based Surveillance

“…This immunoassay employs a signal/cutoff (S/CO) ratio of 1.1 for positivity, while a S/CO of less than 1.1 is reported as negative. The immunoassay detects IgG antibodies to the spike protein of SARS-CoV-2 with 90% sensitivity (95% confidence interval (CI): 76.4–96.4) and 100% specificity [ 12 ]. We obtained the results of all anti-SARS-CoV-2 ELISA IgM and IgG tests performed by the laboratory between 15 July 2020 and 10 July 2021 (12 months).…”

Seroprevalence of SARS-Cov-2 Antibodies in Adults, Arkhangelsk, Russia

“…According to the manufacturer, the assay has a sensitivity of 72% when performed 6–12 days after infection and ≈100% at 13–20 days ( 6 ). An independent assessment of the Vector Best ELISA assay found a sensitivity of 89% and a specificity of 100%, derived from comparisons of test results in prepandemic samples (negative controls) and PCR positive samples for SARS-CoV-2 ( 7 ). We estimated seroprevalence adjusted for test performance (89% sensitivity, 100% specificity) using the equation (crude prevalence + test specificity − 1)/(sensitivity + specificity − 1) ( 8 ).…”