Myotonic Dystrophy Health Index: Initial evaluation of a disease‐specific outcome measure

Abstract

Introduction In preparation for clinical trials we examine the validity, reliability, and patient understanding of the Myotonic Dystrophy Health Index (MDHI). Methods Initially we partnered with 278 myotonic dystrophy type-1 (DM1) patients and identified the most relevant questions for the MDHI. Next, we used factor analysis, patient interviews, and test-retest reliability assessments to refine and evaluate the instrument. Lastly, we determined the capability of the MDHI to differentiate between known groups of DM1 participants. Results Questions in the final MDHI represent 17 areas of DM1 health. The internal consistency was acceptable in all subscales. The MDHI had a high test-retest reliability (ICC=0.95) and differentiated between DM1 patient groups with different disease severities. Conclusion Initial evaluation of the MDHI provides evidence that it is valid and reliable as an outcome measure for assessing patient-reported health. These results suggest that important aspects of DM1 health may be effectively measured using the MDHI.

The Impact of Pregnancy on Myotonic Dystrophy: A Registry-Based Study

“…Questions from the MDHI-SF were included to assess disease burden and symptom severity in the six months prior to the first pregnancy, during the first pregnancy, and in the six months following the first pregnancy. The MDHI-SF is a short form of the Myotonic Dystrophy Health Index (MDHI) [9]. The MDHI is a validated patient-reported outcome measure designed to measure the most relevant symptomatic issues in myotonic dystrophy.…”

“…Both DM1 and DM2 cause muscle weakness, delayed muscle relaxation (myotonia), and early onset cataracts [7, 8]. In addition, both disorders may affect the heart, cognition, and other body systems [9]. Genetic anticipation can lead to expansion in the CTG repeat in DM1.…”

“…In addition, this study utilizes the Myotonic Dystrophy Health Index-Short Form (MDHI-SF) to retrospectively estimate the impact pregnancy has on disease burden in DM [9]. Approval for this study was obtained through the local institutional review board and an ethical approval process through both registries.…”

Report of the second Outcome Measures in Myotonic Dystrophy type 1 (OMMYD-2) international workshop San Sebastian, Spain, October 16, 2013

“…This disease-specific patient reported outcome measure was created using input from over 300 DM1 patients [8,9]. The MDHI is designed to satisfy FDA patient-reported outcome measure guidelines for use in support of drug labeling claims [10].…”

“…It has an acceptable test-retest reliability (ICC = 0.95) and can differentiated between cohorts of DM1 patients suspected to have a higher burden of disease [8]. Standard values based on gender, age, duration of disease, and CTG repeat length are available.…”