Background: Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disorder with symptoms presenting within the first year of life. In recent years, several treatments aimed at slowing disease progression have become commercially available and numerous clinical trials evaluating next generation treatments are underway. Functional assessments designed and validated to assess ambulatory and upper extremity function in boys and men with DMD are typically useful in a portion of the full cohort. The Neuromuscular Gross Motor Outcome (GRO) was designed to assess motor function across wide-ranging functional abilities. Items are scored on a 3-point Likert scale from 0 (or unable) to 2-points (fully achieved) up to a maximum score of 100.
Objective: We sought to evaluate the utility of the GRO in quantifying function in boys and men from birth through adulthood.
Results: A total of 100 patients (mean age: 10.4 years, range: 6 months to 29.5 years) diagnosed with DMD and not participating in an ongoing investigational clinical trial were enrolled. Patients completed a battery of testing at 1 study visit which included the GRO and other traditional functional assessments feasible for their age and functional level. A majority of the cohort was ambulatory (57%); with 3% pre-ambulatory, 12% being transitional, and 27% non-ambulatory. All patients obtained a valid GRO score at the study visit (mean score: 62 points, range: 7-94 points), while only a portion could complete other common assessments: 75% North Star Ambulatory Assessment, 63% Performance of Upper Limb, 16% Bayley gross motor scale. GRO was highly and significantly correlated with all cohort-specific assessments (r>0.8, P<0.001) and patient- and/or parent-reported outcomes (r>0.7, P<0.001). The impact of corticosteroids and other approved treatments on function will be presented.
Conclusions: GRO quantifies motor ability across the age span in DMD in our cross-sectional sample. Test-retest and longitudinal data collection is ongoing.