Japanese translation and validation of the 12-item Multiple Sclerosis Walking Scale version 2

Disability in ambulation has a critical impact on activities of daily living in patients with multiple sclerosis (MS). The 12-item Multiple Sclerosis Walking Scale (MSWS-12) is a self-reported instrument developed to assess the impact of MS on walking. The scale's 12 items assess various aspects of walking-related tasks during the past 2 weeks. MSWS-12 has been used in multiple clinical studies and translated into several languages. In the present study, we translated the MSWS-12 into Japanese and evaluated its psychometric properties in a cross-sectional study.

The original English MSWS-12 version 2 (v2) was translated into Japanese through a standard procedure. Sixty consecutive Japanese MS patients completed the newly prepared Japanese MSWS-12v2 questionnaire and repeated the test 14 days later. Physical disability was assessed by the Expanded Disability Status Scale (EDSS), Timed 25-foot Walk (T25FW), and 9-hole Peg Test (9HPT). Cognitive performance was evaluated using the Processing Speed Test (PST). Fatigue and health-related quality of life were assessed using the Japanese versions of the Fatigue Severity Scale (FSS) and the Functional Assessment of MS (FAMS).

The mean age of the patients was 42.5 years, with median disease duration of 10 years, and median EDSS of 2.0 (range 0, 6.5). Forty-seven patients (78.3 %) had relapsing-remitting, 9 (15.0 %) had secondary-progressive, and 4 (6.7 %) had primary-progressive phenotypes. The median score of the MSWS-12v2 was 5.95 (interquartile range 0, 50.6). Twenty-seven patients (45 %) scored the lowest possible score (0 points), while one (1.7 %) scored the highest possible score (100 points). Cronbach's alpha was 0.98 (95 % confidence interval [CI] 0.97, 0.98), and the test-retest intraclass correlation was 0.95 (95%CI 0.94, 0.96). MSWS-12v2 score was strongly correlated with EDSS (Spearman's ρ = 0.73 [95%CI 0.58, 0.83]), T25FW (ρ = 0.70 [95%CI 0.55, 0.81]), and total FAMS score (ρ = -0.80 [95%CI -0.88, -0.69]), and moderately correlated with 9HPT (ρ = 0.65 [95%CI 0.47, 0.77] for the dominant hand; ρ = 0.62 [95%CI 0.43, 0.75] for the non-dominant hand), PST (ρ = -0.65 [95%CI -0.78, -0.47]), and FSS (ρ = 0.68 [95%CI 0.52, 0.80]). Among the subcomponents of FAMS, the mobility subcomponent showed the most robust correlation with MSWS-12v2 score (ρ = -0.91 [95%CI -0.94, -0.81]). In patients with minimal or no objective disability (EDSS < 3.0, n = 40), only the mobility subcomponent of FAMS was strongly correlated with MSWS-12v2 score (ρ = -0.76 [95% CI -0.87, -0.58]). In contrast, correlations of MSWS-12v2 score with EDSS and T25FW were weak in this subgroup (ρ = 0.28 [95%CI -0.03, 0.55] for EDSS; ρ = 0.25 [95%CI -0.06, 0.52] for T25FW). Response patterns for the single items showed that 32.5 % of the patients with EDSS below 3.0 reported having problems with balance, followed by climbing stairs and standing while doing things (both 25 %).

The Japanese version of the MSWS-12v2 developed in this study is reliable, valid, and helpful for screening walking disability in Japanese MS patients, including those with minimal objective disability.