Validity and responsiveness of the World Health Organization Disability Assessment Schedule II to assess disability in rheumatoid arthritis patients.

OBJECTIVE: To investigate the validity and responsiveness of the World Health Organization Disability Schedule II (WHODAS II) in patients with established RA.
METHODS: In 85 RA patients admitted for rehabilitation, the WHODAS II (0-100) was applied at admission and 6 weeks after discharge. Additional assessments included measures of physical and psychological functioning, disease activity and quality of life. The internal consistency of the WHODAS II was determined with Cronbach's-alpha. Associations between the WHODAS II and other outcome measures were determined by Pearson's rank correlation coefficients. Responsiveness measures included the standardized response mean (SRM), effect size (ES) and responsiveness ratio (RR).
RESULTS: Cronbach's-alpha of the WHODAS II total score was 0.91. The baseline WHODAS II total score correlated significantly with all other outcome measures, except for the 50-feet walk test, the timed-stands test and the Escola Paulista de Medicina Range of Motion scale. The mean WHODAS II total score improved from 40.5 (s.d. 14.9) at baseline to 4.6 at 6 weeks after discharge (95% CI -8.1, -1.2). The WHODAS II responsiveness scores were -0.35 (SRM), -0.34 (ES) and -0.58 (RR) at 6 weeks after discharge. CONCLUSION; The WHODAS II appeared to be internally consistent, valid and responsive to assess disability in patients with established RA admitted for multidisciplinary team care in terms of International Classification of Functioning, Disability and Health. The WHODAS II showed significant floor effects regarding the subscales--'understanding communicating' and 'getting along with people'. In a multidisciplinary setting, the additional use of measures to evaluate personal and environmental factors seems warranted.