B-065 Comparative Analysis of 14-3-3η Autoantibody Assays on Luminex Platform for Diagnosing Axial Spondyloarthritis

Abstract

Abstract Background The pathophysiological significance of extracellular 14-3-3η antigen and its autoantibodies (AAbs) is well-documented in autoimmune rheumatologic disorders. Use of 14-3-3η protein blood tests is common in diagnosing and managing rheumatoid arthritis (RA). Prior studies have established the diagnostic and prognostic value of 14-3-3η AAbs in RA and axial spondyloarthritis (AS), particularly in differentiating AS patients from healthy individuals and in relation to disease severity and progression. This study explores the performance of a novel assay platform in the context of AS diagnosis, especially in younger patients who are most responsive to early treatment interventions.This research aims to evaluate the discriminative accuracy of the 14-3-3η AAb assay on the Luminex® platform, a widely recognized clinical tool, in distinguishing AS patients from healthy subjects, and to compare its performance with that of the Meso Scale Discovery® (MSD) research-use only (RUO) platform. Methods Sera from 49 AS patients and 25 healthy controls (HC), previously assessed using the MSD platform, were reanalyzed using a new Luminex 14-3-3η AAb assay. These samples were sourced from the Follow Up Research Cohort in Axial Spondyloarthritis (FORCAST) Prognostic Cohort. Spearman correlations were employed for variable analysis, and the Mann-Whitney U-test was used to compare AAb levels between groups. Receiver Operating Characteristic (ROC) Area Under Curve (AUC) analyses were conducted for both assay platforms, with a specific focus on patients aged 45 and under. Results The AS patient group had a mean age (SD) of 44 (13) years, with 67% male representation. The median (IQR) disease duration was 19 (10-24) years, and median (IQR) C-reactive protein (CRP) levels were 9.6 (4.3 - 24.8) mg/L. Median (IQR) 14-3-3η AAb levels were significantly higher in AS patients at 136 U/μl (48 - 408) compared to HCs at 54 (28 - 161) U/μl, p=0.02. ROC AUC analysis for the MSD RUO platform showed an AUC of 0.67 (95% CI, 0.55 - 0.79), and for the Luminex platform, an AUC of 0.66 (95% CI, 0.53 - 0.80), indicating comparable performance across platforms. In the subgroup of AS patients aged ≤45 years, the Luminex assay demonstrated an AUC of 0.74 (95% CI, 0.61-0.88), p=0.003. Combination of 14-3-3η AAbs and CRP was able to identify 90% of AS patients. No correlation between the two markers was observed (r= -0.14, p=0.38). Conclusions The Luminex-based 14-3-3η AAb assay exhibits equivalent discriminative capability to the MSD RUO assay in differentiating AS patients from healthy individuals. The combined use of 14-3-3η AAbs and CRP, identifying 90% of AS patients, highlights the potential of these biomarkers as complementary diagnostic and prognostic tools in AS, meriting further research.