Objective: To evaluate the reliability and validity of the PedsQL 3.0 Neuromuscular Module (NMM) in assessing health-related quality of life in the Duchenne muscular dystrophy (DMD) population for use as a secondary outcome measure in phase III clinical trials.
Background: DMD is the most common genetic form of muscular dystrophy in childhood. Clinical trials are underway to evaluate modalities of treatment. The NMM was developed based on interviews of patients with DMD and spinal muscular atrophy. To determine the PedsQL reliability and validity, we administered the NMM to patients with DMD and their caregivers.
Design/methods: Boys 8 to 18 years old with DMD were recruited from a neuromuscular disease clinic. At baseline, the child and caregiver completed the NMM and the PedsQL 4.0 Generic Core Scales (GC). The NMM was repeated 2 to 6 weeks later. Reliability was assessed using Cronbach's coefficient alpha (internal consistency) and intraclass correlation (ICC) (test-retest consistency). Construct validity was assessed by comparing baseline child and caregiver NMM total scores with the GC Total Score, forced vital capacity, cardiac ejection fraction, and ambulatory status.
Results: Forty-four children and their caregivers completed the study. Internal consistency reliability of the total scale score of the NMM was demonstrated (Child alpha = 0.85; Caregiver alpha = 0.87). Test-retest reliability of the NMM was also demonstrated (Child ICC = 0.75, P = 0.001; Caregiver ICC = 0.85, P < 0.001). Validity of the total scale score of the NMM when compared with the GC Total Scale Score was supported (Child r (41) = 0.63, P < 0.001; Caregiver r (42) = 0.64, P < 0.001). Validity of the NMM compared with forced vital capacity was also supported (Child r (38) = 0.35, P = 0.032; Caregiver r (39) = 0.41, P = 0.01). The NMM parent-proxy-report and child self-report "About My Child's Neuromuscular Disease" scale was significantly related to wheelchair use (P < 0.008 and 0.016, respectively); the GC "Child Self-Report "Physical Health" scale was also significantly related to wheelchair use (P < 0.001). We were unable to conduct any analysis with ejection fraction because of the small number of children across all categories.
Conclusions: The PedsQL NMM is a reliable measure of disease-specific health-related quality of life in the DMD population and may be used as an outcome measure in clinical trials.