The Methotrexate Intolerance Severity Score (MISS) questionnaire is used to identify intolerance to methotrexate (MTX), but it is not available in the Brazilian Portuguese language.
The aim of this study was to adapt and validate the MISS in Brazilian Portuguese.
The Brazilian Portuguese version of the MISS was developed following the Guidelines for the Process of Cross-cultural Adaptation of Self-report Measures. The new version was tested in 120 patients with rheumatoid arthritis. For the reliability assessment, the Cronbach α coefficient was used. The receiver operating characteristic curve was constructed with the objective of finding the best cutoff point for MTX intolerance and weighing the sensitivity and specificity. The concordance among the results was analyzed using the κ coefficient and factorial analysis with varimax rotation.
This methodological study developed and applied a culturally acceptable Brazilian Portuguese version of the MISS. The MISS questionnaire presented internal consistency classified as "very good" because Cronbach α is equal to 0.83 (95% confidence interval, 0.79-0.87). The suitability of the data for factorial analysis was demonstrated using the Kaiser-Meyer-Olkin sample adequacy test (KMO = 0.723) and Bartlett sphericity test (χ2 = 499.98, p < 0.001). It was observed that a factorial analysis with 3 factors is preferred; the receiver operating characteristic curve of the MISS score was considered the cutoff point at 6 points (sensitivity 100% and specificity 89.4%).
The Brazilian Portuguese version of the MISS is valid and reliable for the detection of MTX intolerance in clinical practice.