Validity and reliability comparison of 4 mobility measures in patients presenting with neurologic impairment

Objective: To establish the reliability and validity of 4 mobility measures in neurologically impaired adults undergoing rehabilitation. Design: Repeated assessment of same patients. Setting: Two specialized neurologic centers in England. Patients: Forty-six patients with neurologic disabilities selected from inpatient and outpatient rehabilitation centers who were able to stand and walk at least 10 meters, with some aid if needed. Interventions: Patients were assessed twice, at an interval of 7 days, by the same person at the same location. Validity and reliability of each measure were compared by means of scatterplots, Bland-Altman method, and correlation coefficients. Validity was also established by comparing groups of patients expected to differ in mobility. Main Outcome Measures: The Rivermead Mobility Index (RMI) standard version and a version with 4 levels of answer, the 10-meter timed walk, and the 2-minute walk test. Results: The measures showed significant intercorrelation, suggesting that all were valid mobility measures. Each was reasonably reliable, with no evidence of systematic bias. The revised RMI was less sensitive to differences. The distance covered in the 2-minute walk test was significantly decreased for patients using aids (p <.0005) and those with impaired leg sensation (p =.02). Conclusions: All 4 measures tested (2 RMI versions, 1-meter timed walk, 2-minute walk test) showed similar validity and reliability, and the 4-level RMI version failed to show an increased ability to detect differences. All measures showed more disability in patients using aids and those with sensory impairment.