Comparison of six COVID-19 serology assays for detection of antibodies from patients infected with ancestral and a spectrum of SARS-CoV-2 variants.

Serology assays against spike, receptor binding domain (RBD) and nucleocapsid proteins of the severe acute respiratory syndrome coronavirus 2 are essential for serosurveillance. We performed a comparison of four medium-to-high throughput commercial assays [Abbott Laboratories, Ortho Clinical Diagnostics, Meso Scale Diagnostics (MSD)], one point-of-care test (ZEKMED) and a laboratory-developed plaque reduction neutralization test using a reference panel and clinical specimens. Overall, the assays showed a high positive percent agreement of ≥85% and negative percent agreement of ≥90%, with the MSD anti-spike IgG assay having the best performance (100% in both). Notably, Abbott anti-nucleocapsid IgG, MSD anti-spike IgG and ZEKMED anti-spike RBD IgM/IgG combined assays were able to detect antibodies from individuals infected with all different variants tested - Alpha, Beta, Gamma, Delta and Omicron. The limit of detection (LOD) of the assays ranged from 9.9 to 62.0 BAU ml^-1, with the Abbott anti-spike RBD having the lowest LOD. The COVID-19 serology assays will continue to be useful in determining seroprevalence from infection and vaccination.