Analytical assessment of Beckman Coulter Access anti-SARS-CoV-2 IgG immunoassay

Ruscio, M.; D'Agnolo, E.; Belgrano, A.; Plebani, M.; Lippi, G.

Background. The approach to diagnosing, treating and monitoring severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection relies strongly on laboratory resources, with serological testing representing the mainstay for studying the onset, nature and persistence of humoral immune response. This study was aimed at evaluating the analytical performance of the novel Beckman Coulter anti-SARS-CoV-2 IgG chemiluminescent immunoassay. Methods. This analytical assessment encompassed the calculation of intra-assay, inter-assay and total imprecision, linearity, limit of blank (LOB), limit of detection (LOD), functional sensitivity, and comparison of anti-SARS-CoV-2 antibodies values obtained on paired serum samples using DiaSorin Liaison SARS-CoV-2 S1/S2 IgG and Roche Elecsys Anti-SARS-CoV-2 total antibodies. Diagnostic performance was also tested against results of molecular testing on nasopharyngeal swabs, collected over the previous 4 months. Results. Intra-assay, inter-assay and total imprecision of Beckman Coulter anti-SARS-CoV-2 IgG were between 4.3-4.8%, 2.3-3.9% and 4.9-6.2%, respectively. The linearity of the assay was excellent between 0.11-18.8 antibody titers. The LOB, LOD and functional sensitivity were 0.02, 0.02 and 0.05, respectively. The diagnostic accuracy (area under the curve; AUC) of Beckman Coulter anti-SARS-CoV-2 IgG compared to molecular testing was 0.87 (95% CI, 0.84-0.91; p<0.001) using manufacturer's cut-off, and increased to 0.90 (95% CI, 0.86-0.94; p<0.001) with antibody titers. The AUC was non-significantly different from that of Roche Elecsys Anti-SARS-CoV-2, but was always higher than that of DiaSorin Liaison SARS-CoV-2 S1/S2 IgG. The correlation of Beckman Coulter Access SARS-CoV-2 IgG was 0.80 (95% CI, 0.75-0.84; p<0.001) with Roche Elecsys Anti-SARS-CoV-2 and 0.72 (95% CI, 0.66-0.77; p<0.001) with DiaSorin Liaison SARS-CoV-2 S1/S2 IgG, respectively. Conclusions. The results of this analytical evaluation of Beckman Coulter Access anti-SARS-CoV-2 IgG suggests that this fully-automated chemiluminescent immunoassay represents a valuable resource for large and accurate seroprevalence surveys.