OBJECTIVES: To evaluate composite measures of response without acute-phase reactants in RA patients. Specifically, Clinical Disease Activity Index (CDAI)-derived response criteria were compared with the European League Against Rheumatism (EULAR) response criteria, and the modified ACR (mACR) response criteria were compared to the ACR response criteria.

METHODS: Data from 10 108 RA patients enrolled in the Consortium of Rheumatology Researchers of North America registry were examined, including 649 patients initiating DMARD therapy. CDAI cut-off points for disease activity levels and responses were derived using receiver operating characteristic curves with the DAS28 and EULAR response criteria as gold standards. The kappa-statistics were applied to assess agreement between CDAI-derived and EULAR-defined responses, as well as ACR20 and ACR50 with mACR20- and mACR50-defined responses, respectively.

RESULTS: For the components of the EULAR response, the derived CDAI cut-off points for DAS28 levels of 3.2 and 5.1 were 7.6 and 19.6, respectively. The derived CDAI cut-off points were 4.3 and 10.0 for DAS28 changes of 0.6 and 1.2, respectively. There were moderate to substantial agreements between CDAI-derived and EULAR responses (kappa = 0.57-0.71). Agreement of ACR20 and ACR50 with mACR20 and mACR50 responses, respectively, was excellent (kappa = 0.88-0.95).

CONCLUSIONS: Agreement between composite measures of response without acute-phase reactants and standard measures ranged from moderate to excellent. The mACR20 and mACR50 criteria as well as CDAI-derived response criteria, can serve as composite measures of response in clinical practice and research settings without access to acute-phase reactants.