S1564 High Diagnostic Accuracy of Anti-Integrin αvβ6 IgG Serology in Differentiating Ulcerative Colitis From Acute Diarrheal Illnesses in Endemic Settings: A Prospective Diagnostic Accuracy Study

Introduction: Ulcerative colitis (UC) and acute infectious diarrhea (AD) frequently present with overlapping clinical features such as increased stool frequency, haematochezia, urgency, etc. complicating early diagnosis—particularly in regions where enteric infections are endemic and invasive diagnostics are not readily available. While anti-integrin αvβ6 IgG autoantibodies have shown high diagnostic utility in distinguishing UC from Crohn’s disease and healthy controls, their value in differentiating UC from AD—a frequent and clinically relevant challenge—remains unexplored. Methods: In this prospective, single-center diagnostic accuracy study, 112 adults were enrolled: 44 with UC, 44 with AD, and 24 healthy controls (HC). Serum anti-αvβ6 IgG levels were measured using a standardized ELISA (MBL, Japan), with antibody titres quantified against a 7-point calibration curve using 4-parameter logistic regression model. A diagnostic cut-off was defined as the mean + 3 SD of values in the HC cohort. Test performance was assessed using sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Correlations with disease activity indices and inflammatory markers were evaluated. Results: The mean age was 27.5 ± 13.4 years in UC, 34.5 ± 8.7 years in AD, and 39.4 ± 10.7 years in HC groups, with male predominance in the UC cohort (68.2%). Anti-αvβ6 seropositivity was observed in 95.4% of UC patients vs 31.8% with AD, yielding a sensitivity of 95.4% (95% CI: 84.5–99.4), specificity of 68.2% (52.4–81.4), PPV of 75.0% (65.9–82.3), NPV of 93.7% (79.2–98.3), and AUC of 0.916. Antibody titres correlated positively with CRP (r = 0.31, P = 0.043), but not significantly with SCCAI, partial Mayo, or UCEIS. The assay maintained performance across disease phenotypes and medication use. Conclusion: Anti-αvβ6 IgG demonstrates excellent sensitivity and NPV in differentiating UC from acute diarrhea, reinforcing its potential as a non-invasive diagnostic adjunct in ambiguous presentations. To our knowledge, this is the first study evaluating its performance in a cohort where acute diarrheal syndromes are prevalent. Future multicenter studies are warranted to validate these findings and assess its role in reducing diagnostic delays and unnecessary endoscopies in high-burden regions.