Gastroenterology · Medical Literature
[Articles] HLA-DRB1*01:03 in patients with inflammatory bowel disease: a genotype–phenotype association study
Abstract
HLA-DRB1*01:03 emerges as a genetic determinant of severe disease in both patients with Crohn's disease and patients with ulcerative colitis. Although further validation is needed, assessing HLA-DRB1*01:03 carriage might help identify patients who could benefit from more intensive monitoring or earlier use of advanced therapies, aiming to modify the disease course to which they are genetically predisposed.
Clinical relevance
Does carriage of the HLA-DRB1*01:03 allele serve as a genetic determinant of severe disease outcomes — including surgical intervention, perianal complications, and advanced therapy use or failure — across the full spectrum of IBD phenotypes (Crohn's disease, ulcerative colitis, and IBD unclassified)? __SNAPSHOT__ {"studyDesign":"Genotype–phenotype association study (retrospective analysis of prospectively recruited cohort data)","setting":"More than 100 UK hospitals; participants recruited into the NIHR IBD BioResource and UK IBD Genetics Consortium cohorts between 2005 and 2025","sampleSize":"n = 43,762 patients with IBD; HLA-DRB1*01:03 carriers: n = 2,009 (4.6%)","population":"Patients with IBD (Crohn's disease, ulcerative colitis, or IBD unclassified) of inferred European ancestry recruited across the UK","intervention":"Carriage of the HLA-DRB1*01:03 allele (identified via genotyping/imputation from the NIHR IBD BioResource and UK IBD Genetics Consortium datasets)","comparator":"Non-carriers of HLA-DRB1*01:03 within the same IBD cohorts","primaryOutcome":"Association of HLA-DRB1*01:03 carriage with IBD subphenotypes and disease-related adverse outcomes across the full spectrum of IBD (including colonic resection, colectomy, perianal disease, advanced therapy use, advanced therapy failure, and hospitalization), assessed in adjusted models","followUp":"Not reported as a fixed follow-up duration; time-to-event (survival) analyses incorporated longitudinal data spanning the full recruitment window (2005–2025)","fundingSource":"Non-profit/government: Wellcome Trust, NIHR, Medical Research Council, Open Targets, Crohn's & Colitis UK, Helmsley Charitable Trust, Crohn's in Childhood Research Association; partial industry involvement: AstraZeneca's Centre for Genomics Research"}
Key findings
Of 43,762 patients with IBD, 4.6% (n = 2,009) carried HLA-DRB1*01:03. In adjusted models, allele carriage was associated with multiple severe disease outcomes across IBD phenotypes. In Crohn's disease (CD): colonic resection (OR 1.35, 95% CI 1.07–1.69), perianal disease (OR 1.65, 95% CI 1.42–1.92), and advanced therapy use (OR 1.33, 95% CI 1.12–1.58). In ulcerative colitis or IBD unclassified (UC/IBDU): colectomy (OR 1.99, 95% CI 1.63–2.43), perianal disease (OR 1.70, 95% CI 1.27–2.28), advanced therapy use (OR 2.17, 95% CI 1.86–2.52), and hospitalization (OR 1.96, 95% CI 1.67–2.30). Time-to-event analyses demonstrated that HLA-DRB1*01:03 carriers developed perianal CD earlier (HR 1.61, 95% CI 1.24–2.07), required colonic surgery sooner in CD (HR 1.43, 95% CI 1.13–1.82), and underwent colectomy earlier in UC/IBDU (HR 1.69, 95% CI 1.33–2.14). Carriers also initiated their first advanced therapy earlier in both CD (HR 1.37, 95% CI 1.18–1.59) and UC/IBDU (HR 1.82, 95% CI 1.53–2.16), and had increased risk of advanced therapy failure across all IBD phenotypes (HR 1.23, 95% CI 1.02–1.50). P-values and NNT/NNH were not reported. The allele was also associated with younger age of onset in UC/IBDU and older age of onset in CD. No significant association with extraintestinal manifestations was identified in this larger dataset, contrasting with smaller prior studies. The association of HLA-DRB1*01:03 with perianal disease is reported as a previously unreported finding.
Practice implications
This is the largest genotype–phenotype study in IBD to date and comprehensively extends the previously recognized association of HLA-DRB1*01:03 with severe UC to encompass CD and multiple adverse outcomes. The study establishes consistent, statistically significant associations between this allele and surgical intervention, perianal complications, advanced therapy use, and advanced therapy failure. What the study does NOT establish: (1) causality or a specific biological mechanism linking HLA-DRB1*01:03 to these outcomes; (2) the incremental predictive value of HLA-DRB1*01:03 beyond existing clinical risk stratification tools; (3) whether genotype-guided management alters outcomes (no interventional data are presented); (4) cost-effectiveness or feasibility of routine pharmacogenetic testing. Critically, the cohort was restricted to patients of inferred European ancestry, substantially limiting generalizability to South Asian, East Asian, Black/African, and other non-European IBD populations, in whom HLA-DRB1*01:03 frequency and associated risk may differ. The association with perianal disease is novel and hypothesis-generating. Authors themselves call for further validation before clinical implementation. Only an abstract was available at the time of initial analysis; the full publication (Lancet Gastroenterol Hepatol, 2026;11:660–671) is now accessible, and findings cited here are sourced from the full article as reported across multiple secondary sources. Practice should not change yet — this is compelling but requires prospective validation of clinical utility before routine HLA typing can be recommended. __LIMITATIONS__ Restricted to patients of inferred European ancestry; findings may not be generalizable to non-European IBD populations, where HLA-DRB1*01:03 frequency differs,Retrospective genotype–phenotype design is susceptible to selection and ascertainment bias; causality cannot be inferred,HLA-DRB1*01:03 carrier frequency is low (~4.6%), limiting statistical power for some subgroup analyses and raising concerns about generalizability at a population level,Primary outcomes (surgical intervention, advanced therapy use) are composite clinical markers that reflect both disease biology and evolving treatment paradigms over the 20-year recruitment window; unmeasured confounding by treatment era is possible,No prospective or interventional component — the study cannot demonstrate that genotype-guided management improves outcomes,Incremental predictive performance of HLA-DRB1*01:03 over established clinical risk factors was not formally quantified (e.g., no C-statistic or net reclassification improvement reported),Advanced therapy failure definition and ascertainment methods not detailed in available secondary sources,Partial industry involvement (AstraZeneca) and multiple authors with pharmaceutical industry conflicts of interest; risk of framing bias cannot be excluded,NNT, NNH, and absolute risk differences were not reported, making direct assessment of clinical importance difficult,The novel association with perianal disease requires independent replication before clinical acceptance __BOTTOM_LINE_CATEGORY__ potentially_practice_informing __BOTTOM_LINE__ In this large UK genotype–phenotype study of 43,762 IBD patients, carriage of HLA-DRB1*01:03 — present in approximately 1 in 22 patients — was consistently associated with earlier and more severe disease outcomes across both Crohn's disease and ulcerative colitis, including higher odds of colectomy, colonic resection, perianal disease, advanced therapy need, and advanced therapy failure. These findings are biologically plausible and clinically compelling, but prospective validation of the allele's incremental predictive value, cost-effectiveness analyses, and interventional trials are required before routine HLA-DRB1*01:03 testing can be recommended in IBD clinical practice.