Psychometric properties of the activities-specific balance confidence scale among individuals with a lower-limb amputation

Objective: To evaluate the internal consistency, test-retest reliability, and construct validity of the Activities-specific Balance Confidence (ABC) Scale among people who have a lower-limb amputation. Design: Retest design. Setting: A university-affiliated outpatient amputee clinic in Ontario. Participants: Two samples of individuals who have unilateral transtibial and transfemoral amputation. Sample 1 (n=54) was a consecutive and sample 2 (n=329) a convenience sample of all members of the clinic population. Interventions: Not applicable. Main Outcome Measures: Repeated application of the ABC Scale, a 16-item questionnaire that assesses confidence in performing various mobility-related tasks. Correlation to test hypothesized relationships between the ABC Scale and the 2-minute walk (2MWT) and the timed up-and-go (TUG) tests; and assessment of the ability of the ABC Scale to discriminate among groups based on amputation cause, amputation level, mobility device use, automatic stepping ability, wearing time, stair climbing ability, and walking distance. Results: Test-retest reliability (intraclass correlation coefficient) of the ABC Scale was 91 (95% confidence interval [CI], .84-.95) with individual item test-retest coefficients ranging from .53 to .87. Internal consistency, measured by Cronbach alpha, was .95. Hypothesized associations with the 2MWT and TUG test were observed with correlations of .72 (95% Cl,.56-.84) and -.70 (95% CI, -.82 to -.53), respectively. The ABC Scale discriminated between all groups except those based on amputation level. Conclusions: Balance confidence, as measured by the ABC Scale, is a construct that provides unique information potentially useful to clinicians who provide amputee rehabilitation. The ABC Scale is reliable, with strong support for validity. Study of the scale's responsiveness is recommended.