Development of an Automated Chemiluminescence Assay System for Quantitative Measurement of Multiple Anti-SARS-CoV-2 Antibodies

Objectives: Serological tests for COVID-19 have been instrumental in studying the epidemiology of the disease However, the performance of the currently available tests is plagued by the problem of variability We have developed a high-throughput serological test capable of simultaneously detecting total immunoglobulins (Ig) and immunoglobulin G (IgG) against nucleocapsid protein (NP) and spike protein (SP) and report its performance in detecting COVID-19 in clinical samples Methods: We designed and prepared reagents for measuring NP-IgG, NP-Total Ig, SP-IgG, and SP-Total Ig (using N-terminally truncated NP (DELTAN-NP) or receptor-binding domain (RBD) antigen) dedicated automated chemiluminescent enzyme immunoassay analyzer AIA-CL1200 After determining the basal thresholds based on 17 sera obtained from confirmed COVID-19 patients and 600 negative sera, the clinical validity of the assay was evaluated using independent 202 positive samples and 1,000 negative samples from healthy donors Results: All of the four test parameters showed 100% specificity individually (1,000/1,000;95%CI, 99 63-100) The sensitivity of the assay increased proportionally to the elapsed time from symptoms onset, and all the tests achieved 100% sensitivity (153/153;95%CI, 97 63-100) after 13 days from symptoms onset NP-Total Ig was the earliest to attain maximal sensitivity among the other antibodies tested Conclusion: Our newly developed serological testing exhibited 100% sensitivity and specificity after 13 days from symptoms onset Hence, it could be used as a reliable method for accurate detection of COVID-19 patients and to evaluate seroprevalence and possibly for surrogate assessment of herd immunity