Comparative Evaluation of COVID-19 Antibody Assays

Six different assays were utilized in this study: one PRNT, three sVNT assays, and two binding assays. The three sVNT assays used in this study were the cPass SARS-CoV-2 neutralization antibody detection kit (hereafter, GS), the AFIAS COVID-19 nAb kit (Boditech Med, Chuncheon, Gangwon-do, South Korea) (hereafter, BM), and the standard F SARS-CoV-2 nAb fluorescent immunoassay (FIA) (SD Biosensor, Suwon, Gyeonggi-do, South Korea) (hereafter, SD). The two semiquantitative binding assays utilized in this study were the Elecsys anti-SARS-CoV-2 S kit (Roche Diagnostics, Rotkreuz, Switzerland) (hereafter, Roche) and the AdviseDx SARS-CoV-2 IgG II Quant kit (Abbott Laboratories, Abbott Park, IL, USA) (hereafter, Abbott). The PRNT using wild-type SARS-CoV-2 was carried out by the Korea Disease Control and Prevention Agency, and the detailed procedure for the PRNT is described in our previous publication (8 (link), 11 (link)). The PRNT was considered positive for a 50% neutralizing dose (ND₅₀) of ≥20. Other commercial sVNT and binding assays were conducted following the manufacturer’s instructions at Samsung Medical Center, Seoul, South Korea. The cutoffs of the GS, BM, SD, Roche, and Abbott assays suggested by the manufacturers were ≥30%, ≥30%, ≥20%, 0.82 BAU/mL, and 7.1 BAU/mL, respectively.