The responsiveness of health status measures in patients with rheumatoid arthritis: Comparison of disease-specific and generic instruments

Objective. To compare the responsiveness of 2 disease-specific questionnair es, the Modified Health Assessment Questionnaire (MHAQ) and the Arthritis i mpact Measurement Scale (AIMS') with corresponding dimensions (physical fun ction, mental health, pain, and fatigue) in a generic health status measure [the MOS Short Form-36 (SF-36)] in patients with rheumatoid arthritis (RA) . Methods. Within the framework of an observational study, a prospective coho rt of 595 patients with RA from a community based patient register responde d to a questionnaire at baseline and after 2 years' followup. Changes in pa tient global disease activity assessed on a categorical verbal rating scale (range 1-5) were used as external indicator of improvement or deterioratio n. Responsiveness was evaluated with standardized response means (SRM), cal culated as mean change score divided by the standard deviation of the mean change score. Results. Changes in patient global disease activity were classified as much better (n = 33), slightly better (n = 108), no change (n = 291), slightly worse (n = 108), and much worse (n = 20). There were no significant differe nces in responsiveness between SF-36 and the disease-specific measures with in the same dimensions of health. The SRM of the tools within the dimension of pain (AIMS2 and SF-36) were moderate (0.5-0.8) to large (> 0.8) consist ently in both directions (improvement and deterioration). The physical func tion subscales detected the same pattern, but the magnitude of the gradient s was smaller. The fatigue and mental health subscales did not show any cle ar and consistent pattern of change. Conclusion. In patients with RA, there was no difference in responsiveness of subscales from SF-36 and disease-specific instruments when using changes in patient assessed global disease activity as an external indicator of ch ange in health status. The dimension of pain was most sensitive to changes in patient assessed global disease activity followed by physical function, fatigue, and mental health.