Rasch Analysis of the Activities-Specific Balance Confidence Scale in Individuals Poststroke

Abstract

Objective: To examine the psychometric properties of the Activities-specific Balance Confidence (ABC) scale using Rasch analysis for individuals poststroke. Design: Retrospective cohort. Setting: Data was extracted from the Locomotor Experience Applied Post-Stroke phase 3, multisite, randomized controlled clinical trial. Participants: Community-dwelling, ambulatory, older adults (N=406) (mean age ± SD, 61.97±12.76y; 45.07% female) approximately 2 months poststroke. Intervention: None. Main Outcome Measures: We examined unidimensionality, local dependence, rating-scale structure, item and person fit, person-item match, and separation index of the ABC scale. Results: Confirmatory and exploratory factor analysis showed the ABC scale was adequately unidimensional and 3-item pairs had local dependence. A collapsed 5-category rating scale was superior to the 101-category scale. The hardest item was “walking outside on an icy sidewalk,” the easiest item was “getting into or out of a car,” and no items misfit. The ABC scale had high person reliability (0.93), despite 10.5% of individuals misfitting the expected response pattern. Mean ability level of the sample was slightly lower (−0.56 logits) than the mean item difficulty indicating that the ABC scale adequately matched our sample’s balance confidence. The ABC scale did not have a floor or ceiling effect and separated individuals into 5 statistically distinct strata (separation index=3.71). Conclusions: The Rasch model supports the use of the ABC scale to measure balance confidence in individuals poststroke. The consistency of our results with previous Rasch analyses on the ABC scale demonstrates the instrument responds similarly across multiple populations; community-dwelling older-adults, outpatient orthopedic physical therapy, stroke, Parkinson disease, and lower-limb amputation. Recommendations include collapsing the rating scale and developing a computerized-adaptive test version of the scale to enhance clinical utility. Keywords: Postural balance, Psychometrics, Rehabilitation, Stroke