LAUSR

Background: Autoantibodies (AAbs) are important biomarkers for the diagnosis of Autoimmune Diseases (ADs). The detection of AAbs performed by current methods (indirect immunofluorescence test (IIFT)/Immunoblot (dot/line)/enzyme-linked immunosorbent assay ELISA) which have limitations in terms of performing multiple assays to arrive at laboratory diagnosis. We validated a novel multiplex bead-based assay (NMBA) that could quantify five common antibodies, simultaneously, on a flow-cytometry platform. Methods: A total of five recombinant antigens (SS-A Ro60, CENP B, RNP 70, Scl 70 and Histones) were covalently coupled onto beads and tested using known positive sera (positive for AAbs) and analyzed using flow cytometer. Results: The sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) were obtained for each antigen, analyzed by both assays (NMBA and IIFT). It showed comparable or higher values for the NMBA. The Spearman's rank correlation coefficient (Rho) were ≥ 0.97, (P < .05), indicating that multiplexing of the five autoantigens did not alter the results obtained when antigens were tested individually. The mean intra-assay precision measured by coefficient of variation (CV) was7.56 ± 1.6% and the mean inter-assay CV was 10.03 ± 1.34%. The time taken from sample receipt to reporting of results was 90 minutes in NMBA as compared to 150 minutes of IIFT Conclusion: The NMBA could quantitatively measure antibodies against five autoantigens, simultaneously in patient's sera. The assay is faster, objective, reproducible, requires low sample volume, and stable. Moreover, the flow cytometer in diagnostic laboratory settings for hematological and transplant immunology tests, can also be used for testing AAbs.