ASSESSMENT OF DISABILITY WITH THE WHODAS II IN PATIENTS WITH ANKYLOSING SPONDYLITIS

Background: The World Health Organization (WHO) has recently revised the International Classification of Impairments, Disabilities and Handicaps (ICIDH) from a medical model towards a more bio-psycho-social model: the International Classification of Functioning and Disability (ICF). To measure functioning and disability, the WHO has developed a measure that is conceptually compatible with the ICF: the WHO Disability Assessment Schedule II (WHODAS II). The WHODAS II is a generic instrument designed to compare across different interventions and different disease entities.Objectives: To investigate whether the WHODAS II is an appropriate instrument for measuring disability in ankylosing spondylitis (AS), to define its sensitivity to change, and to identify factors that are associated with short-term and long-term changes of scores on the WHODAS II.Methods: Altogether 214 patients with AS from a randomized controlled trial assessing the efficacy of spa therapy (n=117, short-term assessment) and from a longitudinal observational study (n=97, long-term (5 years) assessment) participated. The patients completed several self-administered questionnaires, including the WHODAS II, and underwent physical examination. Thirty-one patients from the spa therapy trial completed a second questionnaire after a 3-week course of spa therapy. Correlation coefficients were calculated to determine the relationship between the WHODAS II and questionnaires as well as measures of physical examination. Responsiveness was calculated by effect size (ES) and standardized response mean (SRM). Linear regression analysis was performed to investigate which factors are associated with a short-term change on the WHODAS II and to investigate which factors predict the WHODAS II score 5 years later.Results: The WHODAS II was acceptable to patients and easy to complete. Mean score on the WHODAS II was 23.9 ± 15.5 (range 0.0 to 76.1). Scores on the WHODAS II were significantly correlated with questionnaires on disease activity, functioning and quality of life (all p<0.001), but not with most measures of physical examination. The WHODAS II showed a moderate short-term responsiveness score (SRM 0.41; ES 0.39), comparable with responsiveness scores for different other questionnaires. Regression analysis showed that short-term change on the WHODAS II is significantly associated with change in functioning (beta coefficient 4.252 (95% confidence interval 1.240-7.264), p=0.007). Disease activity (beta coefficient 0.35 (0.17-0.53), p<0.000) and functioning (beta coefficient 0.23 (0.09-0.38), p=0.002) appeared to significantly predict WHODAS II scores 5 years later.Conclusion: The WHODAS II is an appropriate instrument to measure disability in AS. It is sensitive to detect changes after an efficacious intervention. A short-term change on the WHODAS II is associated with a change in function. Baseline levels of disease activity and functioning can predict WHODAS II scores 5 years later.Citation: , volume , supplement , year 2002, page Session: Spondylarthropathies including psoriatic arthritis 2