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There is a link between the presence of the HLA DQA1-05 allele and the development of anti-TNF antibodies. Testing for the HLA DQA1-05 variant makes it possible to isolate patients with a high immunogenic risk under anti-TNF therapy, but its sensitivity and specificity are insufficient to propose precise algorithms based on the results. This test, therefore, remains a decision-support tool. Elevated IFX clearance identifies the patients at greatest risk of requiring a colectomy to treat severe acute colitis.