MISS questionnaire in French version: a good tool for children and parents to assess methotrexate intolerance

The aim of this study was to assess the relevance for children and parents to use the French-validated version of the methotrexate intolerance severity score (MISS), a measure of methotrexate intolerance for children suffering from juvenile idiopathic arthritis. The French-version MISS was developed following the “Guidelines for the process of cross-cultural adaptation of self-report measures.” The new version was tested in families of children with juvenile idiopathic arthritis who completed the questionnaire twice at a 2-week interval. Item correlations, Cronbach’s alpha, and kappa coefficients were computed to evaluate acceptability, internal consistency, and reproducibility. A culturally acceptable version to French was obtained. A total of 71 individuals were included from May 2015 to November 2015. The results show very good acceptability: good response rate (80%), few missing data (<1%) and good understanding of parents and children. The inter-item, dimension-item, and inter-dimension correlations were satisfactory (except for “vomiting” items–other items correlation). Cronbach’s alpha coefficient was well higher than the usually recommended value of 0.6. The results of validity of internal and external consistencies were satisfactory. We also found good agreement between the test-retest for every family. The empirical discriminative cut-off point of 3 showed a sensitivity of 86% and a specificity of 83%. The MISS questionnaire is quick to complete, easy to use. It can be completed by children or their parents with no significant difference. This validated French-version MISS can help study prevalence and risk factors of methotrexate intolerance, better detect this intolerance, and provide better support for patients on long-term treatment.