Mesalazine is an effective drug for treating ulcerative colitis (UC), but causes allergic symptoms in a few cases. Therefore, the objective of this study was to evaluate the usefulness of the drug-induced lymphocyte stimulation test (DLST) for the diagnosis of mesalazine allergy.

Patients with UC treated with mesalazine with or without a history of associated adverse events (AEs) were enrolled at Kyorin University Hospital from July 2016 to April 2017.

The DLST was performed in 104 patients with UC, of which 24 had a history of AEs due to mesalazine treatment. The control value of DLST was 337.4±296.3 counts per minute (cpm) in the AE⁺ group and 408.0±371.9 cpm in the AE⁻ group. The measured value of DLST was 578.8±424.7 cpm in the AE⁺ group and 476.5±471.8 cpm in the AE⁻ group. The stimulation index (SI) was 243.9%±291.1% in the AE⁺ group and 119.8%±53.0% in the AE⁻ group. The SI value and DLST positivity were significantly higher in the AE⁺ group than in the AE⁻ group ( P =0.030 and P =0.029, respectively). The test sensitivity and specificity were 0.240 and 0.805, respectively, and the false-positive and false-negative rate was 0.195 and 0.760, respectively.

The DLST for mesalazine showed low sensitivity and high specificity, suggesting that it may be useful for the definitive diagnosis of allergy to mesalazine.