In a recent study titled “Long Term Natural History Data in Ambulant Boys with Duchenne Muscular Dystrophy: 36-Month Changes,” a research team from the Department of Pediatric Neurology at the Catholic University in Rome, Italy examined the changes at 3 years follow-up in a 6-minute walk test in patients Duchenne muscular dystrophy, the most used primary outcome measure in international multi center clinical trials for patients with the disease. The study is published in the journal PLOS One.
There has been an increasing interest to develop effective therapeutical approaches for patients affected by Duchenne muscular dystrophy (DMD). Much attention has been devoted to natural history studies and to the identification of possible trajectories of progression of the disease. The 6-minute walk test (6MWT) is currently being used as the primary outcome measure in most of the ongoing studies as it provides a global assessment of functional mobility, endurance, and ability to walk. The North Star Ambulatory Assessment (NSAA) a motor functional scale specifically developed for DMD, is also often used as a secondary measure, providing additional information on several functional aspects that reflect everyday life activities.
In order to assess the spectrum of changes at 3 years in the individual measures, their correlation with steroid treatment, age and 6-minute walk test values at baseline, in their study Eugenio Mercuri and his colleagues evaluated 96 patients with Duchenne muscular dystrophy at baseline and 12, 24 and 36 months.
Results revealed that 3% of the patients lost their capacity to perform the test after 12 months, 14% lost the capacity between 12 and 24 months and 12% lost the ability to execute the test between 24 and 36 months. There was an overall decline in the capacity to perform the 6 minute walk test of −15.8 meters at 12 months, of −58.9 meters at 24 months and of −104.22 meters at 36 months. These longitudinal changes were statistically different between the two baseline age groups and also according to the baseline 6-minute walk test values below 350 meters and above 350 meters. The results also revealed that the changes on the capacity were statistically different when the researchers controlled for steroid treatment.
In the study, the researchers mention that this was the first study to assess longitudinal changes in the 6-minute walk test at 36 months and also to use North Star Ambulatory Assessment in Duchenne muscular dystrophy. According to the team, the results can help clinicians to understand the progression of the disease. The data from this study can also be used to establish comparisons with data of long term extension studies that are becoming available.