Diagnostic performance of two commercially available coronavirus disease 2019 antibody kits: Elecsys Anti-SARS CoV-2 (Roche) and Anti-SARS-CoV-2 ELISA (IgG) (Euroimmun)

Although coronavirus disease 2019 (COVID-19) is no longer a pandemic, it still kills. The risk of a new wild variant means it is still important to monitor and assess the level of immunity in vulnerable populations. We aimed to investigate the diagnostic performance of two widely available commercial antibody testing kits. A total of 170 blood samples with different disease profiles were collected. Sensitivity, specificity, positive-predictive value (PPV), negative-predictive value (NPV), accuracy, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and kappa values were calculated. Receiver-operating characteristic (ROC) analyses of sensitivity and 1-specificity were performed. The area under the curve (AUC) was calculated and P less than 0.05 was considered significant. The positive likelihood ratio LR+ [sensitivity/(1 - specificity)] as a measure of the diagnostic performance of a test was calculated. Spearman's rank correlation analysis was used to compare kit results. For the Roche and Euroimmun tests, the sensitivity was 96 and 89%, the specificity was 100 and 100%, PPV was 100 and 100%, and NPV was 57 and 33%, respectively. AUC was 0.983 for Roche (P < 0.001) and 0.94 for Euroimmun (P < 0.001). A highly significant correlation between the two kits was found (r = 0.917, P < 0.001). Even though the Elecsys Roche kit had a slightly better performance, both kits could be used for the antibody screen of a population. However, combined methods, including memory T-cell and neutralizing antibody tests, can give a better idea of an individual's immune status.