The Myotonic Dystrophy Health Index (MDHI) is a disease-specific, patient reported outcome measure for myotonic dystrophy type-1 (DM1). Each question in the MDHI was selected based on its relevance to a large DM1 population, its ability to be consistently understood by patients, its reliability during test-retest evaluation, its content validity, its face validity, its construct validity, and its responsiveness in detecting therapeutic change. FDA guidelines were implemented during instrument development in order to allow the MDHI to be utilized to support drug labeling claims. The instrument is capable of measuring the total health of a myotonic dystrophy patient as well as seventeen additional areas of relevant DM1 subhealth. Subscales of the MDHI measure a patient’s perception of their health as it relates to: 1) Mobility; 2) Upper Extremity Function; 3) Ability to do Activities; 4) Fatigue; 5) Pain; 6) Gastrointestinal Issues; 7) Vision; 8) Communication; 9) Sleep; 10) Emotional Issues; 11) Cognitive Impairment; 12) Social Satisfaction; 13) Social Performance; 14) Myotonia; 15) Breathing; 16) Swallowing; and 17) Hearing. Overall, the MDHI is optimally suited to detect small but clinically relevant changes in several key areas of myotonic dystrophy health over the course of a treatment trial.
ApplicationsThis MDHI is designed for use as a primary or secondary outcome measure during myotonic dystrophy clinical trials. Alternatively, the MDHI may be used as a marker of disease severity for patients with myotonic dystrophy.
AdvantagesThis MDHI is a validated instrument capable of measuring clinically meaningful changes in patient health during clinical trials. As a disease-specific instrument, this outcome measure focuses on the symptoms that are most important to myotonic dystrophy patients while excluding questions that are less relevant. The content validity, face validity, construct validity, convergent validity, test retest reliability, and responsiveness of this instrument has been previously evaluated in preparation for the MDHI’s use in drug labeling applications.