BACKGROUND: DMD is a rare neurodegenerative disease dramatically affecting HRQoL. Utility scores (dead=0 and full health=1) reflect preferences for the HRQoL implications of specific health states. While published HUI utility values for ambulatory boys range from 0.65-0.75, utilities for non-ambulatory boys are 0.18-0.21. Existing utility data derive from cross-sectional surveys and longitudinal estimates from clinically well-characterized samples are unavailable.
METHODS: Family members serving as proxy respondents for placebo-treated ambulatory boys with DMD, recruited under NCT01254019 (provided by BioMarin Pharmaceuticals Inc), completed the HUI3; resultant utility scores were computed. Mean (standard deviation [SD]) utility values were estimated at baseline and 48 weeks, by ambulatory status and age. Among patients with loss of ambulation (LOA), mean (SD) utility values were calculated across patient-visits post-LOA; and drivers of changes in utility explored by comparing mean attribute scores at baseline vs. after LOA.
RESULTS: At baseline, the mean (range) age was 8.0 (5-16) years. Mean (SD) utility was 0.82 (0.20) among boys aged 5 to <8 years (n=28), and 0.82 (0.19) among boys 8 to 16 years (n=32). At 48 weeks mean (SD) utility was 0.80 (0.19) among those 5 to <8, and 0.71 (0.23) among those aged 8 to 16, years. The mean (SD) utility after LOA (n=6; 9.8%) was 0.35 (0.15), based on a mean decline in utility of 0.25. Change in ambulation levels explained 88% of the drop in utility after LOA, while change in emotional status explained 11%.
CONCLUSIONS: Estimated utility scores for boys with DMD in both ambulatory and non-ambulatory health states were higher than published HUI3 estimates, despite considerable variability. While the utility of younger boys remained relatively stable, older boys and those losing ambulation experienced important declines over follow-up.