Translation and validation in Italian of the methotrexate intolerance severity score for children and adults with arthritis.

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: We translated and adapted the MISS to the Italian language. The Italian MISS showed a very good internal consistency as shown by a Cronbach α of 0.87 (95% CI, 0.84-0.90) and a composite reliability of 0.89 (95% CI, 0.83-0.91).The Cohen's κ was 0.81 (95% CI, 0.71-0.91), suggesting a very good construct validity. The ROC analysis showed an area under the curve (AUC) of 0.97 (95% CI, 0.93-0.99). A threshold of 6 to define intolerant patients, showed a sensitivity of 98.3% and specificity of 81.2%.

Conclusions: 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.