Variability of objective gait measures across the expanded disability status scale in people living with multiple sclerosis: A cross-sectional retrospective analysis

Background: The Expanded Disability Status Scale (EDSS) is widely utilized in clinical trials and routine care to evaluate disease burden and progression among people with multiple sclerosis (pwMS). However, instrumental gait measures may be more suitable than EDSS to track walking disability in pwMS. In this cross-sectional study, we aimed to quantify the variability of spatiotemporal gait measures within homologous EDSS categories. Methods: A total of 205 pwMS (age=46.5[SD=10.5] years, 72.2% female, EDSS range=1.0–6.5) were studied in this retrospective analysis. Participants underwent walking assessments through the GAITRite system and the following spatiotemporal gait measures were recorded: gait speed, mean normalized velocity (MNV), base of support, stride length, step length, percentage of gait cycle spent in double support and single support, and functional ambulation profile. The EDSS was evaluated by a certified neurologist. Results: All gait measures exhibited fair to very strong correlations with scores on the EDSS (-0.81≤ρ_s≤0.25) and poor to fair correlations with disease duration (-0.32≤ρ_s≤0.17). Overall, the percent variability of gait measures increased across EDSS categories, with coefficients of variation ranging from 6.9% to 37.2% in the minimal disability group (EDSS≤2.5), 8.1% to 33.4% and 22.3% to 53.8% in the moderate (2.5<EDSS≤4.5) and severe (EDSS>4.5) disability groups, respectively. Conclusion: Spatiotemporal gait measures have great variability within homologous EDSS categories. The high percent variability of gait speed and MNV (up to more than 50%) suggests that walking ability varies substantially within and across disability levels. Therefore, in addition to the EDSS, more comprehensive (multidimensional), objective patient-centric metrics would be needed to accurately evaluate disability in pwMS.