Reliability, validity, and agreement of the short-form Activities-specific Balance Confidence Scale in people with lower extremity amputations

Background: Clinicians use the Activities-specific Balance Confidence Scale to understand balance confidence. A short-form Activities-specific Balance Confidence scale, was developed using the six most difficult tasks from the original Activities-specific Balance Confidence scale; however, short-form the short-form scale psychometrics and agreement with the original scale have yet to be explored in people with lower extremity amputations.

Objective: To determine the relative and absolute reliability, construct validity, and agreement of the short-form Activities-specific Balance Confidence scale.

Study design: Test-retest with a 2-week interval.

Methods: Analysis for relative reliability and internal consistency was intraclass correlation coefficient and Cronbach's α, respectively. Absolute reliability was measured using standard error of measurement and minimal detectable change. Bland-Altman plots measured agreement between scales. Construct validity was evaluated against the L Test using a Pearson-product moment correlation.

Results: The short-form Activities-specific Balance Confidence (intraclass correlation coefficient = 0.92) and Activities-specific Balance Confidence (intraclass correlation coefficient = 0.91) scales had excellent relative reliability. Both scales demonstrated good internal consistency. Worse absolute reliability was observed in the short-form Activities-specific Balance Confidence scale. Construct validity against the L Test was confirmed. Bland-Altman plots indicated poor agreement between scales.

Conclusion: Both scales exhibit excellent relative reliability and good internal consistency and construct validity. Poor agreement between short-form Activities-specific Balance Confidence and Activities-specific Balance Confidence indicates the scales should not be used interchangeably. Inadequate absolute reliability of the short-form Activities-specific Balance Confidence scale suggests the Activities-specific Balance Confidence should be the balance confidence scale of choice.

Clinical relevance: Balance confidence is an important metric for our understanding of rehabilitation and community re-integration in people with lower extremity amputations. Due to inferior absolute reliability and a lack of appropriate items composing the short-form Activities-specific Balance Confidence scale, the full-scale Activities-specific Balance Confidence is recommended for the assessment of balance confidence in this population.