The L test of functional mobility: measurement properties of a modified version of the timed "up & go" test designed for people with lower-limb amputations

BACKGROUND AND PURPOSE: Walk tests provide essential outcome information when assessing ambulation of individuals with lower-limb amputation and a prosthetic device. Existing tests have limitations such as ceiling effects or insufficient challenge. The objective of this study was to assess the reliability and validity of data for a clinical measure of basic mobility, the L Test of Functional Mobility (L Test). SUBJECTS: For this methodological study, 93 people with unilateral amputations (74% transtibial, 26% transfemoral; 78% male, 22% female; mean age=55.9 years) were consecutively recruited from an outpatient clinic. Twenty-seven subjects returned for retesting. METHODS: To assess concurrent validity, subjects completed the L Test, Timed "Up & Go" Test (TUG), 10-Meter Walk Test, and 2-Minute Walk Test, followed by the Activities-specific Balance Confidence scale, Frenchay Activities Index (FAI), and mobility subscale of the Prosthetic Evaluation Questionnaire (PEQ-MS). Amputation cause and level, walking aid use, automatic stepping, and age variables were used to assess discriminant validity. RESULTS: Intraclass correlation coefficients were .96 for interrater reliability and .97 for intrarater reliability, and minimal bias existed upon retesting. The magnitude of concurrent validity correlations (r) was very high between the L Test data and data for other walk tests and fair to moderate between the L Test data and data for self-report measures. The L Test discriminated between all groups as hypothesized. DISCUSSION AND CONCLUSION: The L Test is a 20-m test of basic mobility skills that includes 2 transfers and 4 turns. It demonstrated excellent measurement properties in this study.