The Myotonic Dystrophy Health Index: Italian validation of a disease-specific outcome measure.

The Myotonic Dystrophy Health Index (MDHI) is a disease-specific, self-reported outcome measure that assesses total disease burden and 17 areas of Myotonic Dystrophy type 1 (DM1) specific health. This study translated the MDHI into Italian and validated the instrument using a cohort of Italian DM1 patients. Italian DM1 patients were interviewed regarding the form and content of the instrument. Thirty-eight DM1 patients were subsequently recruited to test the reliability and concurrent validity of the instrument by serially completing the MDHI and a battery of clinical tests. Lastly, we determined the internal consistency of the Italian MDHI and each of its subscales. The internal consistency was excellent in the total Italian MDHI score and acceptable in all of its subscales; the test-retest reliability was high (intraclass correlation coefficient = 0.95); Italian MDHI total scores and subscales were associated with neuromuscular function, cognitive and social health, respiratory function, and quality of life. Overall, the Italian MDHI is valid and well suited to measure the multi-dimensional aspects of disease burden in Myotonic Dystrophy clinical trials.