Feasibility and validity of the RADAI, a self-administered rheumatoid arthritis disease activity index

Objective. The goal of the Rheumatoid Arthritis Disease Activity Index (RAD AI) is to provide an easy to use assessment of disease activity. It is a se lf-administered questionnaire that combines five items into a single index: current and past global disease activity, pain, morning stiffness and a jo int count. Methods. A sample of 484 rheumatoid arthritis (RA) patients was used to ass ess the internal consistency and the convergent validity of the RADAI. This was achieved by calculating Cronbach's alpha and RADAI item and total scor e correlations with core set measures and DAS28. Results. Cronbach's alpha was 0.87, supporting the summation of the items i nto a single index. The index correlated best with physicians' global asses sment (r = 0.59; P < 0.0001), the Health Assessment Questionnaire (r = 0.55 ; P < 0.0001) and the number of tender joints (r = 0.55; P < 0.0001). Corre lation with the erythrocyte sedimentation rate was low (r = 0.27; P < 0.000 1). The RADAI and the DAS28 were correlated (r = 0.53; P < 0.0001), but the re was low agreement. Conclusions. The RADAI is valid to assess disease activity in RA patients. However, the RADAI may not automatically replace other measures of disease activity, such as the DAS28.