Reliability and validity of step test scores in subjects with chronic stroke

Objectives: To establish (1) the intrarater and interrater reliabilities of step test (ST) scores in subjects with chronic stroke, (2) the ST's known-groups validity and cutoff scores for distinguishing subjects with chronic stroke from healthy adults older than 50 years, and (3) the convergent validity of ST scores with lower-limb muscle strength, coordination, balance performance, and walking speed. Design: Cross-sectional study. Setting: University-based rehabilitation center. Participants: Convenience sample of subjects (N=30): community-dwelling subjects with chronic stroke (n=15) and healthy adults older than 50 years (n=15). Interventions: Not applicable. Main Outcome Measures: ST scores; handheld dynamometer measurements of bilateral lower-limb muscle strength; lower-extremity motor coordination test (LEMOCOT) scores; Berg Balance Scale scores; walking speed as measured by a 5-meter walk test. Results: ST scores showed excellent intrarater reliability, with intraclass correlation coefficients ranging from.981 to.995 and interrater reliability ranging from.996 to.999. A cutoff score of 13 on the paretic side was found to distinguish the healthy adults older than 50 years from subjects with stroke at a sensitivity of 87% and a specificity of 87%. A cutoff score of 11 on the nonparetic side was found to distinguish the healthy adults from subjects with stroke at a sensitivity of 100% and a specificity of 67%. ST scores of the paretic limb demonstrated a significant correlation with muscle strength, the LEMOCOT scores of the paretic leg, and walking speed. ST scores of the nonparetic limb demonstrated a significant correlation with muscle strength and the LEMOCOT scores of the paretic leg. Conclusions: The ST is a reliable measurement tool when the number of steps is counted by either experienced or inexperienced examiners by viewing videotapes. ST scores with both the paretic limb and the nonparetic limb are sensitive in distinguishing subjects with chronic stroke from healthy adults older than 50 years.