The Clinical Disease Activity Index and the Routine Assessment of Patient Index Data 3 for Achievement of Treatment Strategies

Objective: To compare the Clinical Disease Activity Index (CDAI) with the Routine Assessment of Patient Index Data 3 (RAPID3) from 2 large United States registries.

Methods: Using a cross section of clinic visits within 2 registries, we determined whether the outcome of each metric would place the patient in remission (REM), low (LDA), moderate (MDA), or high disease activity (HDA) using the CDAI, with the assumption that a patient in MDA or HDA would be a candidate for acceleration of treatment.

Results: We identified significant disparities between the 2 indices in final disease categorization using each index system. For patients identified in LDA by CDAI, RAPID3 identified 20.4% and 28.3% as LDA in Corrona and the Brigham and Women's Rheumatoid Arthritis Sequential Study (BRASS), respectively. For patients identified as MDA by CDAI, RAPID3 identified 36.2% and 31.1% as MDA in Corrona and BRASS, respectively, with the greatest disparities within each system identified for LDA and MDA activity by the CDAI (20.4% and 36.2% agreement of RAPID3 with CDAI, respectively, in Corrona and 28.3% and 31.1% agreement in BRASS). Overall comparison between CDAI and RAPID3 in the 4 disease categories resulted in estimated κ = 0.285 in both. The RAPID3 scores indicated the potential for treat-to-target acceleration in 34.4% of patients in REM or LDA based on CDAI in Corrona and 27.7% in BRASS, respectively.

Conclusion: The RAPID3, based on patient-reported outcomes, shows differences with CDAI categories of disease activity. The components of CDAI are not highly correlated with RAPID3, except for patient global assessment. These differences could significantly affect the decision to advance treatment when using a treat-to-target regimen.