Diagnostic performance between in-house and commercial SARS-CoV-2 serological immunoassays including binding-specific antibody and surrogate virus neutralization test (sVNT)
Poramed Winichakoon, Jiraprapa Wipasa, Kriangkrai Chawansuntati, Parichat Salee, Tavitiya Sudjaritruk, Saowaluck Yasri, Chantana Khamwan, Rungnapa Peerakam, Dararat Dankai, Romanee Chaiwarith
Abstract
This study aimed to evaluate the correlation between in-house and commercial binding-specific IgG antibodies and between in-house and commercial SARS-CoV-2 surrogate virus neutralization tests (sVNT). Samples from healthcare workers who received vaccines against SARS-CoV-2 were tested for RBD-specific antibody, S-specific antibody, and in-house ELISA, commercial sVNT, and in-house sVNT, against wild-type SARS-CoV-2. Three hundred and five samples were included in the analysis. The correlation between S-specific binding antibodies and in-house ELISA was 0.96 (95% CI 0.96-0.97) and between RBD-specific antibodies and in-house ELISA was 0.96 (95% CI 0.95-0.97). The Cohen's kappa between in-house sVNT and the commercial test was 0.90 (95% CI 0.80, 1.00). If using 90% inhibition of sVNT as the reference standard, the optimal cut-off value of RBD-specific antibodies was 442.7 BAU/mL, the kappa, sensitivity, and specificity being 0.99, 99%, and 100%, respectively. The optimal cut-off value of S-specific antibodies was 1155.9 BAU/mL, the kappa, sensitivity, and specificity being 0.99, 100%, and 99%, respectively. This study demonstrated a very strong correlation between in-house ELISA and 2 commercial assays. There was also a very strong correlation between in-house and commercial SARS-CoV-2 sVNT, a finding of particular interest which will inform future research.