P4.A011: Six-minute peak activity, a novel metric in individuals with Duchenne muscular dystrophy

Background: Duchenne Muscular Dystrophy (DMD) is a progressive disorder leading to muscle wasting, cardiopulmonary failure, and premature death. The six-minute walk test (6MWT) and quantitative muscle testing (QMT) have been previously utilized as outcome metrics, however 6MWT cannot be used in non-ambulatory patients and QMT is effort-dependent. A metric able to measure skeletal muscle progression remotely and independent of patient effort would be significantly advantageous for clinical management and use in clinical trials. Our goal was to evaluate whether six-minute peak activity (6MPA), a novel metric measured using accelerometry, distinguished between ambulatory and non-ambulatory patients and correlated with QMT.

Methods: The median age of the cohort was 12.7 years [10.6, 15.9]; 69 (53%) were ambulatory at baseline; 120 (93%) were taking, or had previously taken, corticosteroids. A total of 139 wears from 83 participants were analyzed. VM percentiles were significantly different across all percentiles for participants classified as ambulatory versus those classified as non-ambulatory at time of wear (Table 1). Median 6MPA declined significantly overall from baseline to final measurement for the 50th, 75th, and 95th percentiles. Ten participants during the study became non-ambulatory, and 6MPA 75th percentile significantly declined after loss of ambulation for this group (Table 1). Significant, moderately strong, associations were observed between 6MPA percentiles and indexed QMT, with the strongest at the 95th percentile (Table 2).

Results: The median age of the cohort was 12.7 years [10.6, 15.9]; 69 (53%) were ambulatory at baseline; 120 (93%) were taking, or had previously taken, corticosteroids. A total of 139 wears from 83 participants were analyzed. VM percentiles were significantly different across all percentiles for participants classified as ambulatory versus those classified as non-ambulatory at time of wear (Table 1). Median 6MPA declined significantly overall from baseline to final measurement for the 50th, 75th, and 95th percentiles. Ten participants during the study became non-ambulatory, and 6MPA 75th percentile significantly declined after loss of ambulation for this group (Table 1). Significant, moderately strong, associations were observed between 6MPA percentiles and indexed QMT, with the strongest at the 95th percentile (Table 2).

Conclusion: 6MPA differentiated ambulatory and non-ambulatory patients with DMD and declined over time, modeling progression of skeletal myopathy. 6MPA also correlated with indexed QMT, particularly at the 95th percentile. 6MPA has potential for future use as an effort-independent clinical outcome of skeletal muscle progression that can be assessed in both ambulatory and non-ambulatory individuals.