Evaluation of drug-induced lymphocyte stimulation test in mesalazine-associated allergic drug reaction.

Background: 5-Aminosalicylic acid (5-ASA) is a fundamental drug for UC management; however, adverse reactions can lead to poor clinical outcomes and increased health care costs. No objective tests currently exist to predict adverse reactions. This study thus investigated 5-ASA across 4 formulations and addressed a key issue in the treatment of mild to moderate ulcerative colitis (UC). Objective: We aimed to examine the utility of the drug-induced lymphocyte stimulation test (DLST) in predicting successful rotation from mesalazine to sulfasalazine (SASP) in patients with UC. Methods: We retrospectively analyzed the largest cohort to date of patients with UC who were suspected of 5-ASA-associated adverse reactions and underwent DLST. We evaluated the DLST positivity rate for the suspected formulation, cross-reactivity to nonsuspected formulations, and clinical outcomes after rotation from mesalazine to SASP. Results: Mesalazine formulations exhibited a DLST positivity rate of 22.0% (18/82), with 45.1% (37/82) of patients testing positive for at least one 5-ASA formulation. Cross-reactivity between mesalazine and SASP was lower at 12.2% (10/82), likely because of structural differences. Adverse reactions typically developed within 2 weeks of initiating 5-ASA and commonly included fever, diarrhea, and bloody stool. Among patients with mesalazine-associated adverse reactions with DLST-negative test result for SASP, 8 of 12 tolerated the rotation. Rotation failure was mainly associated with a positive or borderline DLST result for mesalazine. Conclusions: DLST serves as a useful diagnostic tool for guiding treatment in patients with UC and suspected 5-ASA-associated hypersensitivity reactions. Prospective multicenter studies are needed to validate its clinical utility.