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

## TL;DR

This study evaluates the drug-induced lymphocyte stimulation test (DLST) to predict successful treatment rotation in patients with ulcerative colitis experiencing adverse reactions to mesalazine.

## Contribution

The study provides the largest cohort analysis of DLST for predicting mesalazine hypersensitivity and treatment rotation outcomes.

## Key findings

- Mesalazine formulations showed a 22.0% DLST positivity rate, with 45.1% of patients positive for at least one 5-ASA formulation.
- Cross-reactivity between mesalazine and SASP was low at 12.2%, likely due to structural differences.
- DLST-negative patients had an 8/12 success rate in tolerating rotation to SASP, while failures were linked to positive DLST results.

## Abstract

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).

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.

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.

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.

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.