Measuring balance confidence after spinal cord injury: the reliability and validity of the Activities-specific Balance Confidence Scale.

CONTEXT/OBJECTIVE: The study objectives were to evaluate the test-retest reliability, convergent validity, and discriminative validity of the Activities-specific Balance Confidence (ABC) scale in individuals with incomplete spinal cord injury (iSCI).

DESIGN: Prospective, cross-sectional study.

SETTING: Laboratory.

PARTICIPANTS: Twenty-six community-dwelling individuals with chronic iSCI (20 males, 59.7 + 18.9 years old) and 26 age- and sex-matched able-bodied (AB) individuals participated.

INTERVENTIONS: None.

OUTCOME MEASURES: Measures of balance and gait were collected over two days. Clinical measures included the ABC scale, Mini-Balance Evaluation System's Test, 10-meter Walk Test, SCI Functional Ambulation Profile, manual muscle testing of lower extremity muscles, and measures of lower extremity proprioception and cutaneous pressure sensitivity. Biomechanical measures included the velocity and sway area of centre of pressure (COP) movement during quiet standing.

RESULTS: The ABC scale demonstrated high test-retest reliability (intraclass correlation coefficient = 0.93) among participants with iSCI. The minimal detectable change was 14.87%. ABC scale scores correlated with performance on all clinical measures (ρ=0.60-0.80, P<0.01), with the exception of proprioception and cutaneous pressure sensitivity (P=0.20-0.70), demonstrating convergent validity. ABC scale scores also correlated with overall COP velocity (ρ=-0.69, P<0.001) and COP velocity in the anterior-posterior direction (ρ=-0.71, P<0.001). Participants with iSCI scored significantly lower on the ABC scale than the AB participants (P<0.001), and the area under the receiver operating characteristic curve was 0.95, demonstrating discriminative validity.

CONCLUSION: The ABC scale is a reliable and valid measure of balance confidence in community-dwelling, ambulatory individuals with chronic iSCI.