Patient-centered rheumatoid arthritis disease activity assessment by a modified RADAI

Abstract

Objective: To evaluate the psychometric properties and validity of a modified version of the Rheumatoid Arthritis Disease Activity Index (RADAI) without joint counts in order to facilitate rapid and easy RA activity assessment in daily routine.

Methods: One hundred sixty-nine outpatients with RA completed the original RADAI and the modified RADAI-5. Simultaneously, the Disease Activity Score-28-erythrocyte sedimentation rate (DAS28-ESR) and C-reactive protein (DAS28-CRP) and the Simplified Disease Activity Index (SDAI) and Clinical DAI (CDAI) were applied. Cronbach's alpha, as a measure for internal consistency, and Spearman's rho, to evaluate the linear relationship of the different disease activity scales, were calculated. Rho was determined for the RADAI-5 and the core set measures to assess convergent validity. For agreement analysis, kappa statistics were calculated. An attempt was made to estimate the modified questionnaire's sensitivity to change.

Results: Means for the RADAI and the RADAI-5 were 2.8 (range 0.0-9.12) and 3.07 (0-10), respectively. Other means were as follows: DAS28-ESR 3.51 (0.28-6.67), DAS28-CRP 3.19 (1.12-5.83), CDAI 11.53 (0.0-44.6), and SDAI 12.36 (0.1-44.9). Cronbach's alpha was highest for the RADAI-5 (0.917) and lowest for the DAS28-CRP (0.510). The RADAI-5 was highly significantly correlated (all p < 0.0001) to all other instruments. However, kappa was < 0.65 for the relation of the RADAI-5 and all other scores except the RADAI. Changes of the RADAI-5, DAS28-ESR, and CDAI were significantly correlated (p < 0.001).

Conclusion: The RADAI-5, refraining from joint counts, was shown to be capable of measuring RA activity. Reliability and convergent validity could be proven.