The 3-m backward walk test: reliability and validity in ambulant people with multiple sclerosis

To investigate: (a) the interrater and test–retest reliability of the 3-m backward walk test (3MBW) in ambulant people with multiple sclerosis (PwMS); (b) minimal detectable change (MDC); (c) concurrent and known-groups validity; and (d) the cutoff time to best discriminate fallers from nonfallers with multiple sclerosis (MS). Forty-nine PwMS and 36 healthy people were included in this cross-sectional study. The 3MBW was administered with the timed up and go test, Berg Balance Scale, four square step test, Falls Efficacy Scale-International, and Expanded Disability Status Scale. The 3MBW was simultaneously performed by two independent raters to examine the interrater reliability while was repeated after 7–10 days to examine the test–retest reliability. The 3MBW showed good interrater reliability [intraclass correlation coefficient (ICC) = 0.987–0.989] and excellent test–retest reliability (ICC = 0.854–0.889). The MDC was found to be 1.69 s. The 3MBW had moderate-to-strong correlations with the other measures. For the 3MBW, PwMS had worse performance than healthy people ( P < 0.001), whereas fallers with MS had worse performance than nonfallers with MS ( P < 0.001). The 3MBW time of 7.86 s was determined to best discriminate fallers from nonfallers with MS. The 3MBW is a reliable, simple, and easy-to-administer tool for assessing backward walking among ambulant PwMS.