Background: Methotrexate (MTX) is the most used drug for the treatment of children and adults suffering from arthritis although its intake is burdened by well-known side effects. The Methotrexate Intolerance Severity Score (MISS) was originally developed in English [1] to identify patients intolerant to MTX.

Objectives: Methotrexate (MTX) is the most used drug to treat children and adults with arthritis and its use is burdened by adverse effects. The MTX intolerance severity score (MISS) was developed in English to identify patients who are intolerant to MTX. The aim of this study was to translate and validate the MISS in Italian.

Methods: The Italian version of the MISS was developed following the “guidelines for process of cross-cultural adaptation of self-reported measures”. The Italian version of the MISS was validated in 125 patients with juvenile idiopathic arthritis (JIA) followed at the Rheumatology Unit of Bambino Gesù Children Hospital. We assessed the construct validity and calculated the internal consistency of the Italian MISS. We performed ROC analysis to assess the overall performance of the Italian MISS.

Results: Of the study cohort (83% female), 71 patients had oligoarthritis, 43 had RF-negative polyarthritis, 4 had enthesitis-related arthritis (ERA), and 3 had psoriatic arthritis. The mean age (±IQR) at diagnosis was approximately 4 years, with a “disease duration” on the MISS questionnaire of 6 years (IQR 3.3-10.5). The mean (± SD) VAS and c-JADAS scores were 0.7 and 2.4 respectively, with 65% of patients having inactive disease. The majority (98%) of patients received MTX subcutaneously and the average duration of use of the drug was approximately 5 years. We translated and adapted the MISS to the Italian language. The Italian MISS showed a very good internal consistency as shown by a Cronbach a of 0.87 (95% CI, 0.84-0.90) and a composite reliability of 0.89 (95% CI, 0.83-0.91). A threshold of 6 to define intolerant patients, showed a sensitivity of 98.3% and specificity of 81.2%.

Conclusion: We developed the Italian version of the MISS and showed its validity and reliability to identify patients intolerant to MTX in clinical practice and in a research setting.

REFERENCES: [1] M. Bulatović et al., “High prevalence of methotrexate intolerance in juvenile idiopathic arthritis: development and validation of a methotrexate intolerance severity score.” Arthritis Rheum 63, 2007-2013 (2011).

[2] D. Wild et al., “Principles of Good Practice for the Translation and Cultural Adaptation Process for Patient-Reported Outcomes (PRO) Measures: report of the ISPOR Task Force for Translation and Cultural Adaptation.” Value Health 8, 94-104 (2005).

Acknowledgements: NIL.

Disclosure of Interests: None declared.