Timed Rise from Floor as a Predictor of Disease Progression in Duchenne Muscular Dystrophy: An Observational Study

Abstract

Background: The role of timed items, and more specifically, of the time to rise from the floor, has been reported as an early prognostic factor for disease progression and loss of ambulation. The aim of our study was to investigate the possible effect of the time to rise from the floor test on the changes observed on the 6MWT over 12 months in a cohort of ambulant Duchenne boys.

Subjects and methods: A total of 487 12-month data points were collected from 215 ambulant Duchenne boys. The age ranged between 5.0 and 20.0 years (mean 8.48 ±2.48 DS).

Results: The results of the time to rise from the floor at baseline ranged from 1.2 to 29.4 seconds in the boys who could perform the test. 49 patients were unable to perform the test at baseline and 87 at 12 month The 6MWT values ranged from 82 to 567 meters at baseline. 3 patients lost the ability to perform the 6mwt at 12 months. The correlation between time to rise from the floor and 6MWT at baseline was high (r = 0.6, p<0.01).

Conclusions: Both time to rise from the floor and baseline 6MWT were relevant for predicting 6MWT changes in the group above the age of 7 years, with no interaction between the two measures, as the impact of time to rise from the floor on 6MWT change was similar in the patients below and above 350 m. Our results suggest that, time to rise from the floor can be considered an additional important prognostic factor of 12 month changes on the 6MWT and, more generally, of disease progression.

Fig 1. Individual details of TRF scores (in seconds) and 6MWT results (in meters).

Fig 2. Percentage of patients losing ambulation in subgroups subdivided according to TRF performance.

Fig 3. Average 6MWD change over 12 months according to baseline age (<7 years vs > = 7 years) in those with baseline 6MWD< 350 m and in those with baseline 6MWD> = 350 m.

The significant age by 6MWD interaction (p<0.001) indicates that the baseline value of 6MWD has an impact on the 6MWD change only in children older than 7 years.

Fig 4. Average 6MWD change over 12 months according to baseline age (<7 years vs > = 7 years) in those with baseline TRF < 7 sec and in those with baseline TRF> = 7 sec.

The borderline significant age by TRF interaction (p = 0.06) indicates that the baseline value of TRF has an impact on the 6MWD change only in children older than 7 years.

Fig 5. Average 6MWT change over 12 months according to baseline values of 6MWD (<350 vs > = 350) in those with baseline TRF < 7 sec and in those with baseline TRF > = 7sec.

There is no 6MWD by TRF interaction, indicating that that the baseline value of 6MWD has the same impact on the 6MWD change according to different baseline TRF values.