Construct validity of the walk ratio as a measure of gait control in people with multiple sclerosis without mobility aids

Abstract

Ambulatory limitations are a key component of disability in people with multiple sclerosis (PwMS). Various tools are employed to assess walking performance in PwMS; however, no ideal measure has as yet been attained. In this situation, a walk ratio might be more advantageous compared with other gait measures. The walk ratio, a simple index for describing temporal and spatial co-ordination, denotes the relationship between step length and cadence during walking. Hence, the primary objective of this study was to determine the relationship between the walk ratio and measures of other theoretically related constructs. The walk ratio was studied using the GAITRite™ system (CIR Systems, Inc. Havertown, USA). The study group included 229 PwMS (143 women) and a mean disease duration of 5.8 (SD=7.1) years. The walk ratio score of the total sample was 5.3 (SD=0.8). Significant differences based on the expanded disability status scale (EDSS) scores (F=11.616, P<0.001) were observed between the neurological disability subgroups. Scores of the very mild (EDSS 0-2.0), mild (EDSS 2.5-4.0) and moderate (EDSS 4.5-5.5) groups were 5.5 (SD=0.7), 5.2 (SD=0.7), 4.9 (SD=0.9), respectively. In terms of fall status, the MS fallers demonstrated a significant lower walk ratio compared to the MS non-fallers; 5.1 (SD=0.8) vs. 5.5 (SD=0.7); P<0.001. Modest significant correlation scores were found between walk ratio and ambulation tests. Scores were slightly higher in the short walking tests, timed 25-foot walk and timed up and go tests (Pearson's rho=0.369, 0.364) compared to the 6 and 2-min walk time tests (Pearson's rho=0.344, 0.308). Collectively, the current study supports the construct validity of the walk ratio index in PwMS without mobility aids.

Keywords: Balance; Construct validity; Gait; Multiple sclerosis; Walk ratio.