Immune changes detectable up to a decade before inflammatory bowel disease diagnosis could eventually support earlier risk assessment, according to findings presented at UEG Week 2026. The conditions studied, Crohn's disease and ulcerative colitis, involve abnormal immune responses that cause persistent inflammation and intestinal damage. Researchers analysed 2,000 blood serum samples from 500 participants: 200 who subsequently developed each condition and 100 healthy controls. Samples spanned diagnosis and approximately two, four and 10 years beforehand.
Across reactions to roughly 357,000 antigens—substances recognised by the immune system—the team identified 123,980 distinct antibodies. Future patients displayed reduced antibody diversity, with disease-specific signatures already apparent 10 years before diagnosis. Crohn's disease was associated with elevated responses to herpesviruses and bacterial flagellin, a protein in structures bacteria use for movement. These responses were particularly marked among participants who later developed complicated disease or disease affecting the final section of the small intestine. Ulcerative colitis showed increased responses to herpesviruses and the body's own tissue components. Responses to organisms with protective outer coatings declined in both groups.
Machine-learning models distinguished future Crohn's cases from healthy controls with an area under the curve, or AUC, of 0.90; the corresponding value for ulcerative colitis was 0.84. AUC measures discrimination, with 0.5 equivalent to chance and 1.0 indicating perfect separation. Predicting complicated Crohn's disease approximately 10 years before diagnosis yielded an AUC of 0.85. Although these profiles might help identify patients needing more intensive treatment, routine screening remains premature. Independent, more diverse populations must be studied, and researchers must establish added value beyond existing assessments, develop an affordable, reproducible test and demonstrate improved patient outcomes.
