Validity and reliability of the Portuguese version of the modified Migraine Disability Assessment

Background Migraine Disability Assessment Scale (MIDAS) is a useful tool to measure headache-related disability. Modified MIDAS with 4-week recall period reduces recall bias and improves accuracy of the results. This study aimed at validating mMIDAS in Portuguese. Methods Studied population consisted of adult migraine patients attending a headache outpatient clinic. Reliability was assessed by internal consistency and reproducibility in a 3-week test-retest. Content validity was evaluated by two expert panels. Construct validity was tested by comparing mMIDAS-P index in socioeconomic and clinical patient groups and scale unidimensionality was evidenced by factor analysis. Criterion validity was tested using EQ-5D-5L and HADS. Results Ninety-two patients, 88% female, mean age of 44 years, participated. They had, in average, 9.7 headache days in previous month, pain averaging 7.5/10. About 69.9% were on a migraine prophylactic treatment, and 42.4% had severe disability; 29.4 and 13.0% showed, respectively, moderate/severe anxiety and depression. Content validity showed that mMIDAS-P is simple and clinically useful. It did not show to be determined by patient's sociodemographic characteristics and it was correlated with depression scale and EQ-5D-5L. Test-retest demonstrated high reproductive reliability and good internal consistency. Conclusion mMIDAS-P is valid and reliable. We strongly recommend it for clinical and research use.