Rapid and accurate agglutination-based testing for SARS-CoV-2 antibodies
Sally Esmail, Michael J. Knauer, Husam Abdoh, Courtney Voss, Benjamin Chin‐Yee, P.J. Stogios, Almagul Seitova, Ashley Hutchinson, Farhad Yusifov, T. Skarina, E. Evdokimova, Suzanne Ackloo, Lori E. Lowes, Benjamin D. Hedley, Vipin Bhayana, Ian Chin‐Yee, Shawn S.‐C. Li
Abstract
We have developed a rapid, accurate, and cost-effective serologic test for SARS-CoV-2 virus, which caused the COVID-19 pandemic, on the basis of antibody-dependent agglutination of antigen-coated latex particles. When validated using plasma samples that are positive or negative for SARS-CoV-2, the agglutination assay detected antibodies against the receptor-binding domain of the spike (S-RBD) or the nucleocapsid protein of SARS-CoV-2 with 100% specificity and ∼98% sensitivity. Furthermore, we found that the strength of the S-RBD antibody response measured by the agglutination assay correlated with the efficiency of the plasma in blocking RBD binding to the angiotensin-converting enzyme 2 in a surrogate neutralization assay, suggesting that the agglutination assay might be used to identify individuals with virus-neutralizing antibodies. Intriguingly, we found that >92% of patients had detectable antibodies on the day of a positive viral RNA test, suggesting that the agglutination antibody test might complement RNA testing for the diagnosis of SARS-CoV-2 infection.