DUCHENNE MUSCULAR DYSTROPHY - PHYSIOTHERAPY: P.317Clinically meaningful change on the 100 meter timed test in neuromuscular diseases

Abstract

The 100 meter timed test (100m) is a fixed distance ambulatory assessment used to quantify maximal ambulatory ability in children and adults. The purpose of our study was to establish the minimal clinically important difference (MCID) of the 100m in muscular dystrophies to better interpret results over time and evaluate its utility to predict loss of ambulation (LOA). We collected longitudinal 100m times in cohorts with Duchenne muscular dystrophy (DMD) and limb girdle muscular dystrophies (LGMD) 2E and 2A. The DMD cohort included 149 boys (mean age: 7.7 +/- 2.7 years, range 3.5 to 14.7 years) and LGMD cohort included 45 subjects (mean age: 25.0 +/- 13.6 years, range 2.9 to 55.2 years). All subjects completed the 100m as quickly as possible at one study visit. The time to complete the 100 ranged from 28-217 seconds. A subset (n=90 DMD; n= 28 LGMD) completed the 100m at subsequent visits between 6 months and 2 years after baseline. The MCID for the 100m was calculated as 1/3 the standard deviation of baseline values as well as the standard error of measurement (SEM) approach. The MCID generated for DMD was 8.5 seconds using the most conservative method. Using the MCID 60% of our longitudinal cohort demonstrated a significant decline in ambulation over 12 months. Subgroup analysis of the effect of disease phases, such as young children, ambulatory and transitional ambulatory groups, on MCID will be presented. A 100m time of 100 seconds emerged as a critical value for predicting loss of ambulation in DMD as 75% of the cohort lost ambulation within 1 year when their time to complete 100m increased to over 100 seconds. One hundred percent of the DMD cohort lost walking ability within 1 year (average of 9 months) once their walking time increased over 117 seconds. Differences in the LGMD cohort will be discussed. In conclusion, the 100 meter timed test can be implemented in both pediatric and adult populations and can measure meaningful changes over time.