Gait disorder is one of the most frequent dysfunction reported by patients with multiple sclerosis (PwMS). Studies have shown that fampridine can improve gait velocity in 11.2 to 34.8% of them. The minimal important clinical difference (MICD) on a timed 25-foot test (T25FT) measured by anchor-based methods is around 20%. Considering a more conservative method based on reproducibility and minimal detectable change (MDC), the T25FT cut-off is comprised between 23 and 66%. The aim of this study was to evaluate whether fampridine can overpass PwMS's gait velocity cut-offs determined by a reproducibility approach.

Sixty-eight patients were included (EDSS 4.0 to 6.5) from FAMPISEP (NCT02849782). Each patient was evaluated 3 times (Fig. 1). Gait was evaluated with a GaitRite system and the variables considered were gait velocity on the T25FT under different conditions (comfortable speed, fast speed, dual task with calculation of dual task cost), the timed up and go test and the 6minutes walk test (6MWT). The cut-offs for each variable were determined from the results of the first 2 visits and based on a reproducibility method using the MDC. The percentage of patients under treatment overpassing those cut-offs was calculated.

Table 1 shows the cut-offs of the aforementioned tests and the percentage of patients that overpass those cut-offs. Considering a composite analysis, the percentage of patient that overpass at least one of the cut-offs was 32.4%.

Regarding previous studies, the cut-offs based on MDC are higher than those found with MICD and appear difficult to achieve. This study confirms previous results showing that a small percentage of patients overpass at least 1 cut-off. A recent study has suggested using a composite criterion (using different gait tests). In this case, the percentages of improvement based on MDC are near to those found with the MICD.