24 month longitudinal data in ambulant boys with Duchenne muscular dystrophy

Abstract

Objectives: The aim of the study was i) to assess the spectrum of changes over 24 months in ambulant boys affected by Duchenne muscular dystrophy, ii) to establish the difference between the first and the second year results and iii) to identify possible early markers of loss of ambulation.

Methods: One hundred and thirteen patients (age range 4.1-17, mean 8.2) fulfilled the inclusion criteria, 67 of the 113 were on daily and 40 on intermittent steroids, while 6 were not on steroids. All were assessed using the 6 Minute Walk Test (6MWT), the North Star Ambulatory Assessment (NSAA) and timed test.

Results: On the 6MWT there was an average overall decline of -22.7 (SD 81.0) in the first year and of -64.7 (SD 123.1) in the second year. On the NSAA the average overall decline was of -1.86 (SD 4.21) in the first year and of -2.98 (SD 5.19) in the second year. Fourteen children lost ambulation, one in the first year and the other 13 in the second year of the study. A distance of at least 330 meters on the 6MWT, or a NSAA score of 18 at baseline reduced significantly the risk of losing ambulation within 2 years.

Conclusions: These results can be of help at the time of using inclusion criteria for a study in ambulant patients in order to minimize the risk of patients who may lose ambulation within the time of the trial.

Figure 1. Mean changes in 6MWT and in NSAA scores in patients below the age of 7 years at baseline (grey line) and above (black line).

Figure 2. Risk of losing ambulation within 2 years in relation to different cut-off points of 6MWD and NSAA scores at baseline.