B-064 Analytical and Diagnostic Performances of Anti-Integrin Antibody System in Inflammatory Bowel Disease

Abstract Background Anti-integrin αvβ6 autoantibodies may have value in the diagnosis of Inflammatory Bowel Disease (IBD) and more specifically Ulcerative Colitis (UC). Our objective was to establish the analytical and diagnostic performance of this novel autoantibody system in distinguishing IBD from a group of Normal Healthy Volunteers (NHV) and UC from Crohn’s Disease (CD). Methods All testing was performed using a Tecan Evo200 equipped with 8-channel and 96-channel arms, plate washer, and plate reader. The ELISA assay used calibration controls and diluted serum samples added to ELISA plates coated with Integrin αvβ6 antigen. Anti-human IgG horseradish peroxidase complexed with Anti-integrin αvβ6 antibodies was detected using colorimetry. The analytical performance was evaluated by using repeatability and reproducibility with coefficient of variation (CV) calculated. The diagnostic performances were evaluated by testing specimens collected from consented subjects available from a biobank in autoimmune gastrointestinal diseases. This consisted of 60 NHV, and 187 IBD (91 CD and 96 UC). Sensitivity, specificity, diagnostic odds ratio (OR), positive and negative predictive values (PPV and NPV) were estimated. Results Intra-assay CVs ranged from 1.5% to 5.2% over dynamic range. Inter-assay CVs were below 10%. Median titers were below 5 U/mL for NHV and CD, and 26 U/mL for UC (Fig. 1). Cutoff of 5 U/mL was 100% specific for UC and CD. Sensitivity for UC and CD was 80% (77/96), and 15% (14/91), respectively. Diagnostic Odds Ratio yielded 22.3-fold (95% CI: 10.5–47.5) higher likelihood of UC than CD in the presence of Anti-integrin αvβ6 titers above cutoff, with PPV and NPV values of 84% (76%-90%) and 81% (74%–87%), respectively (50% pre-test). Conclusion We have established the analytical performance of an Anti-integrin αvβ6 autoantibody ELISA assay. These preliminary data suggests that the Anti-Integrin αvβ6 autoantibody system is highly specific for UC with high sensitivity and specificity.