Development and Validation of a Novel, Disease-Specific, Caregiver-Reported Outcome Measure: The Duchenne Muscular Dystrophy Caregiver Reported-Health Index (DMDCR-HI).

AIM: Regulatory-grade outcome measures are essential for supporting future therapeutic trials. The goal of our study was to develop and validate a multifactorial, disease-specific, caregiver-reported outcome (CRO) measure for Duchenne muscular dystrophy (DMD).

METHODS

We conducted qualitative interviews and a cross-sectional study with caregivers of individuals with DMD to determine the most prevalent and impactful symptoms to individuals with DMD. Symptom items were selected for the Duchenne Muscular Dystrophy Caregiver Reported-Health Index (DMDCR-HI) based on their prevalence and impact to a national sample cohort of caregivers, along with their potential ability to respond to therapeutics. Subsequently, we conducted cognitive beta interviews, test-retest reliability assessments, and internal consistency analyses to evaluate and optimize the DMDCR-HI. Using known group analysis, we assessed the ability of the DMDCR-HI to differentiate between patients with differing levels of disease burden.

RESULTS

The DMDCR-HI is a regulatory-grade CRO that comprehensively measures 16 subscales in DMD. The instrument has a high internal consistency, strong test-retest reliability (intraclass correlation coefficient (ICC) = 0.96), and was identified by caregivers as easy to use, relevant, and comprehensive. Through known group analysis, DMDCR-HI scores demonstrated an ability to differentiate between subgroups with varying levels of symptomatic burden.

DISCUSSION: The DMDCR-HI is a valid and reliable CRO designed to sensitively and reliably capture how individuals with DMD feel and function from the perspective of the caregiver. The DMDCR-HI offers a robust mechanism to longitudinally track changes in disease burden in individuals with DMD, regardless of age, cognitive ability, or ambulation status.