Brief clinical evaluation of six high-throughput SARS-CoV-2 IgG antibody assays

Abstract

Serological SARS-CoV-2 assays are urgently needed for diagnosis, contact tracing and for epidemiological studies. So far, there is limited data on how recently commercially available, high-throughput immunoassays, using different recombinant SARS-CoV-2 antigens, perform with clinical samples. Focusing on IgG and total antibodies, we demonstrate the performance of four automated immunoassays (Abbott Architect™ i2000 (N protein-based)), Roche cobas™ e 411 analyzer (N protein-based, not differentiating between IgA, IgM or IgG antibodies), LIAISON®XL platform (S1 and S2 protein-based), VIRCLIA® automation system (S1 and N protein-based) in comparison to two ELISA assays (Euroimmun SARS-CoV-2 IgG (S1 protein-based) and Virotech SARS-CoV-2 IgG ELISA (N protein-based)) and an in-house developed plaque reduction neutralization test (PRNT). We tested follow up serum/plasma samples of individuals PCR-diagnosed with COVID-19. When calculating the overall sensitivity, in a time frame of 49 days after first PCR-positivity, the PRNT as gold standard, showed the highest sensitivity with 93.3% followed by the dual-target assay for the VIRCLIA® automation system with 89%. The overall sensitivity in the group of N protein-based assays ranged from 66.7 to 77.8% and in the S protein-based-assays from 71.1 to 75.6%. Five follow-up samples of three individuals were only detected in either an S and/or N protein-based assay, indicating an individual different immune response to SARS-CoV-2 and the influence of the used assay in the detection of IgG antibodies. This should be further analysed. The specificity of the examined assays was ≥ 97%. However, because of the low or unknown prevalence of SARS-CoV-2, the examined assays in this study are currently primarily eligible for epidemiological investigations, as they have limited information in individual testing.

Keywords: Antibody; Assay; Evaluation; IgG; PRNT; SARS-CoV-2.

Fig. 1

Titers for the examined assays: (a) SARS-CoV-2-IgG (Abbott); (b) Elecsys Anti-SARS-CoV-2; (c) Virotech SARS-CoV-2 ELISA IgG; (d) Anti-SARS-CoV-2-ELISA (IgG) (Euroimmun); (e) Liaison® SARS-CoV-2 S1/S2 IgG; (f) COVID-19 VIRCLIA® IgG MONOTEST; (g) PRNT Titer for tested samples; 1 = samples from one individual, 2 + 3 = samples from two different individuals; bold horizontal lines show assay specific cut-off.