An interim analysis from the PRIMA-102 study evaluated the concordance between two widely used clinical response measures in rheumatoid arthritis (RA)—Clinical Disease Activity Index (CDAI) minimum clinically important difference (MCID) and Disease Activity Score (DAS) 28-CRP–based EULAR response criteria—in a real-world, multimechanism treatment cohort.

The analysis included 636 participants initiating a new biologic or targeted synthetic DMARD, with assessments at baseline and 12 weeks. Of these, 64% achieved a CDAI MCID response, and 68% met moderate or good EULAR response criteria. Agreement between the two measures was substantial across drug classes, with an overall kappa coefficient (κ) of 0.69 (95% CI, 0.63–0.75), consistent across TNFi, JAKi, anti-T-cell, anti-IL-6R, and anti-B-cell therapies.

However, discordant responses occurred in 14% of patients, with 5.3% meeting only CDAI MCID criteria and 8.6% meeting only EULAR criteria. Baseline factors associated with discordance included serostatus, prior treatment lines, joint counts, and global assessments. Change scores associated with discordance showed large effect sizes in swollen joint count, C-reactive protein (CRP), patient visual analogue scale, and provider global assessment.

“There was generally good agreement between CDAI MCID and EULAR Response criteria,” the authors reported, “suggesting that either method could support development of a precision medicine test to predict treatment response.” The results were presented at ACR Convergence.

However, they cautioned that “the higher percentage of positive responses unique to the DAS28-CRP EULAR criteria suggests that EULAR response based on DAS28-CRP may introduce bias when assigning response status for drug classes (e.g., IL-6R) that directly modulate CRP levels.”

For rheumatologists, these findings support the use of both CDAI and EULAR criteria, while highlighting the need for contextual interpretation, especially in therapies that affect inflammatory biomarkers.

Reference
Taylor P, Carlson J, Vu S, Fransen S, Abdueva D, Curtis J. Agreement between two rheumatoid arthritis response measures across b/ts DMARD treatment classes in a large, prospective observational study supporting the development and clinical validation of a novel blood-based precision medicine test [abstract]. Arthritis Rheumatol. 2025; 77 (suppl 9). https://acrabstracts.org/abstract/agreement-between-two-rheumatoid-arthritis-response-measures-across-b-ts-dmard-treatment-classes-in-a-large-prospective-observational-study-supporting-the-development-and-clinical-validation-of-a-nov/