For older boys with Duchenne muscular dystrophy (DMD), the time it takes to rise from the floor is associated with disease progression over 12 months, a new study reports. The findings, published in the journal PLOS ONE, indicate that the measure can be used as a prognostic factor for disease progression.
There is a need, especially in clinical trials, to identify measures that can define the progression of disease in DMD. Several studies have shown that the six-minute walk test (6MWT) can be helpful to identify different disease trajectories, and the measure is often used as a primary outcome in clinical trials. But that measure is highly variable, so complementing it with other tests could reduce the variation.
Boys younger than 7 years may often improve their performance over a year, while older boys generally show a progressive decline. Also, scientists have noted that those who can perform 350 meters or more in the 6MWT are more stable in their disease progression than boys performing less than 350 meters. Combining age and 6MWT results can better predict the disease trajectory over one, two, and three years. An additional measure might further improve the power to predict disease progression.
The study, “Timed Rise from Floor as a Predictor of Disease Progression in Duchenne Muscular Dystrophy: An Observational Study,“ recruited 215 ambulant boys with DMD, ages 5 to 20. The research team measured both 6MWT and the time it takes for a person to rise from the floor from a lying position on their back at the study’s start, and again after 12 months.
The team, from Catholic University in Rome, Italy, then analyzed how the two measures correlated and noted that there was a relatively good agreement between the measures in the low and high range of the 6MWT. In contrast, the two measures did not correlate well in the medium range of 6MWT: 250-400 meters.
When looking at the different age groups – younger or older than age 7 – they found that in the younger boys, the time it took to get up from the floor was a poor predictor of how their 6MWT performance changed over 12 months. In contrast, in the older age group, the 6MWT changes could be predicted by the first measurement of the time to rise from the floor.
The individuals who took more than seven seconds to get up from the floor had more decline in their 6MWT performance. The time it took participants to rise from the floor could, however, not predict loss of ambulation.
The team excluded that the differences could be related to treatment with corticosteroids, since the treatment was equally common in both groups.
The findings suggest that in boys older than 7, the addition of the time to rise from the floor test could improve the estimate of disease progression, a crucial measure when designing clinical trials.