Test-Retest Reliability and Agreement of the Work Ability Index–Single Item in Persons With Physical Disabilities

Abstract

Objective: To assess the test-retest reliability and agreement of the work ability index–single item (WAS) in persons with a physical disability. Design: Test-retest study, with a 2-4 week interval. Test-retest reliability was computed using the intraclass correlation coefficient (ICC). The agreement was analyzed using Bland-Altman plots. Setting: Vocational rehabilitation department of a rehabilitation center. Participants: Patients with a physical disability (spinal cord injury, acquired brain injury, neuromuscular disease, or other). Interventions: Not applicable. Main Outcome Measures: The WAS consists of 1 question on self-reported current work ability compared with their highest work ability ever, rated on a 0-10 scale. Results: Data from 44 patients were available and 22 patients reported no changes in work or medical situation between the 2 measurements. After excluding 1 outlier in this subgroup (n=21), the ICC was 0.89 (95% confidence interval, 0.76-0.96), the mean test-retest difference was −0.05 points and the limits of agreement were ±2.4 points. Conclusions: The WAS is reliable for measuring work ability in persons with a physical disability. Using the WAS could be valuable as a routine outcome measure in vocational rehabilitation for persons with a physical disability.