M.P.3.04 Assessment of StepWatch™ activity monitoring in phase 2b study of ataluren (PTC124™) in nmDMD/BMD

Measuring Habitual Physical Activity in Neuromuscular Disorders: A Systematic Review

BACKGROUND

Free-living or habitual physical activity (HPA) refers to someone's performance in his or her free-living environment. Neuromuscular disorders (NMD) manifest through HPA, and the observation of HPA can be used to identify clinical risks and to quantify outcomes in research. This review summarizes and analyses previous studies reporting the assessment of HPA in NMD, and may serve as the basis for evidence-based decision-making when considering assessing HPA in this population.

METHODS

A systematic review was performed to identify all studies related to HPA in NMD, followed by a critical appraisal of the assessment methodology and a final review of the identified HPA tools.

RESULTS

A total of 22 studies were selected, reporting on eight different direct tools (or activity monitors) and ten structured patient-reported outcomes. Overall, HPA patterns in NMD differ from healthy control populations. There was a noticeable lack of validation studies for these tools and outcome measures in NMD. Very little information regarding feasibility and barriers for the application of these tools in this population have been published.

CONCLUSIONS

The variety and heterogeneity of tools and methods in the published literature makes the comparison across different studies difficult, and methodological guidelines are warranted. We propose a checklist of considerations for the assessment and reporting of HPA in NMD.

Functional level assessment of individuals with transtibial limb loss: Evaluation in the clinical setting versus objective community ambulatory activity

The functional level (K level) of prosthetic users is used to choose appropriate prosthetic components, but ratings may highly subjective. A more objective and robust method to determine K level may be appealing. The aim of this study was to determine the relationship between K level determined in the clinic to K level based on real world ambulatory activity data collected by StepWatch. Twelve individuals with transtibial limb loss gave informed consent to participate. K level assessments performed in the clinic by a single treating prosthetist were compared with a calculated estimate based on seven days of real world ambulatory activity patterns using linear regression. There was good agreement between the two methods of determining K level with R²= 0.775 (p < 0.001). The calculated estimate of K level based on actual ambulatory activity in real world settings appears to be similar to the treating prosthetist’s assessment of K level based on gait observation and patient responses in the clinic. Clinic-based ambulatory capacity in transtibial prosthetic users appears to correlate with real world ambulatory behavior in this small cohort. Determining functional level based on real world ambulatory activity may supplement clinic-based tests of functional capacity.

Strong correlation between the 6-minute walk test and accelerometry functional outcomes in boys with Duchenne muscular dystrophy

Accelerometry provides information on habitual physical capability that may be of value in the assessment of function in Duchenne muscular dystrophy. This preliminary investigation describes the relationship between community ambulation measured by the StepWatch activity monitor and the current standard of functional assessment, the 6-minute walk test, in ambulatory boys with Duchenne muscular dystrophy (n = 16) and healthy controls (n = 13). All participants completed a 6-minute walk test and wore the StepWatch™ monitor for 5 consecutive days. Both the 6-minute walk test and StepWatch accelerometry identified a decreased capacity for ambulation in boys with Duchenne compared to healthy controls. There were strong, significant correlations between 6-minute walk distance and all StepWatch parameters in affected boys only (r = 0.701-0.804). These data proffer intriguing observations that warrant further exploration. Specifically, accelerometry outcomes may compliment the 6-minute walk test in assessment of therapeutic interventions for Duchenne muscular dystrophy.