Longitudinal timed function tests in Duchenne muscular dystrophy: ImagingDMD cohort natural history

Arora H, Willcocks RJ, Lott DJ, et al. Longitudinal timed function tests in Duchenne muscular dystrophy: ImagingDMD cohort natural history. Muscle & nerve  2018;58:631-638.

Arora_2018_Muscle Nerve. Nov;58(5);631-638

Functional performance tests are often used in clinical trials. In this study the natural history data of the performance of these tests was assessed as well as the prediction for functional outcomes, like the loss of ambulation. Three timed function tests (TFT; 10m walk/run, then climbing 4 stairs, then supine to stand (STS)) and the 6-minute walk test (6MWT) were investigated in at different ages, followed over time and compared to healthy boys. Already at young age impaired function was seen compared to controls, which increased over time. In patients below the age of seven no changes were observed after one year, whereas older boys showed a decline in performance. Changed in TFTs were larger than in the 6MWT. For all tests performance at the beginning of the study was a predictor of the loss of function, whereby TFTs were stronger predictors. These findings are important for the planning of clinical trials, e.g.the number of patients needed, and the test to use. For younger patients alternative tests are needed.



INTRODUCTION: Tests of ambulatory function are common clinical trial endpoints in Duchenne muscular dystrophy (DMD). Using these tests, the ImagingDMD study has generated a large data set that can describe the contemporary natural history of DMD in 5-12.9-year-olds.

METHODS: Ninety-two corticosteroid-treated boys with DMD and 45 controls participated in this longitudinal study. Participants performed the 6-minute walk test (6MWT) and timed function tests (TFT: 10-m walk/run, climbing 4 stairs, supine to stand).

RESULTS: Boys with DMD had impaired functional performance even at 5-6.9 years old. Boys older than 7 had significant declines in function over 1 year for 10-m walk/run and 6MWT. Eighty percent of participants could perform all functional tests at 9 years old. TFTs appear to be slightly more responsive and predictive of disease progression than the 6MWT in 7-12.9 year olds.

DISCUSSION: This study provides insight into the contemporary natural history of key functional endpoints in DMD. Muscle Nerve 58: 631-638, 2018.

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