Objective: In this study, we used data from clinical trials of dalfampridine (fampridine outside the United States) to re-examine the clinical meaningfulness of Timed 25-Foot Walk (T25FW) changes.
Methods: Pooled data were analyzed from 2 phase III randomized placebo-controlled clinical trials of dalfampridine in multiple sclerosis (MS) (n = 533). Walking speed (T25FW) and patient-reported walking ability (MS Walking Scale-12 [MSWS-12]) were measured, concurrently, multiple times before and during treatment. We examined T25FW speed variability within and between visits, correlations of T25FW speed with MSWS-12 score, and changes in MSWS-12 (mean scores, effect sizes) associated with percent T25FW changes.
Results: T25FW speed variability was small (within- and between-visit averages = 7.2%-8.7% and 14.4%-16.3%). Correlations between T25FW and MSWS-12 values were low (-0.20 to -0.30), but relatively stronger between their change values (-0.33 to -0.41). Speed improvements of >20%, and possibly 15%, were associated with clinically meaningful changes in self-reported walking ability using MSWS-12 change score and effect size criteria.
Conclusions: This study builds on existing research and provides direct evidence that improvements in T25FW speed of ≥ 20% are meaningful to people with MS. The dalfampridine data enabled examinations previously not possible, including spontaneous and induced speed changes, speed change anchored to change in self-reported walking ability, and a profile of speed changes. Results support the T25FW as a clinically meaningful outcome measure for MS clinical trials.