Prevalence of methotrexate intolerance among patients with rheumatoid arthritis using the Arabic version of the methotrexate intolerance severity score.

Aim: Methotrexate (MTX) is the anchor drug for the treatment of rheumatoid arthritis (RA). MTX is associated with adverse events that limit its use. The MTX intolerance severity score (MISS) was developed to identify symptoms related to MTX use in juvenile idiopathic arthritis and RA patients. The aim of this study is to translate and validate the MISS in the Arabic language.

Methods: Forward and backward translation of the MISS were performed by two fluent Arabic translators and reviewed by three rheumatologists. Consecutive patients with RA who used MTX for ≥3 months were recruited from two tertiary care centers in Riyadh, Saudi Arabia. A test was considered positive if the patient scored ≥6 points. The internal consistency and stability of the items were evaluated using Cronbach's alpha and the test-retest method.

Results: A total of 185 patients were recruited. Of those patients, 158 (85.4%) were female. The mean (±SD) age and disease duration were 49.7 (±12.67) and 8.67 (±7.1) years, respectively. The mean Disease Activity Score of 28 joints was 3.2 (±1.3). Fifty-five (30%) patients were illiterate. Seventy-three (39.5%) patients had a positive MISS. Of those patients, 55 (75.3%) and 18 (24.7%) were using the oral and subcutaneous forms of MTX, respectively. The Arabic MISS had good internal consistency (Cronbach's alpha = 0.792) and a factorable study size for test-retest and factor analysis (Kaiser-Meyer-Olkin = 0.745).

Conclusion: The Arabic MISS showed validity and good reliability in detecting MTX intolerance in RA patients. MTX intolerance is prevalent among RA patients. Larger studies are needed to confirm these findings.