STABILITY OF HEALTH-STATUS MEASUREMENT IN RHEUMATOID-ARTHRITIS

Health status measures in rheumatoid arthritis that have been extensiv ely validated for use in clinical trials are generally used also in co rrelative studies, e.g. to predict future health status. This applicat ion requires stability (repeatability of measurements). The purpose of our study was to determine the stability of commonly used health stat us measures. Two measurements at an interval of 6 months were taken in 99 patients. High stability (alpha = 0.78 to 0.94) was observed for f ive biomedical measures (grip strength, walking time, platelet count, haemoglobin and erythrocyte sedimentation rate) and five self-report m easures (mobility, self care, impact daily activities, anxiety and che erful mood). Moderate stability (alpha = 0.65 to 0.72) was observed fo r joint scores, pain, C-reactive protein and depressive mood. The high ly stable measures most adequately reflect individual differences, may be applied most reliably in correlative studies and appear to have th e largest clinical utility with regard to long-term prediction of heal th status.