The American College of Rheumatology (ACR) hybrid (a modified mean percent response to treatment) was officially recommended by the ACR as a revision to 20%, 50%, and 70% response criteria (ACR20/50/70) scores, but has not been tested in clinical trials. We performed a post hoc analysis of a phase III study of certolizumab pegol (Rheumatoid Arthritis Prevention of Structural Damage 1 [RAPID 1]) using the ACR hybrid.
Patients with active rheumatoid arthritis were randomized to certolizumab pegol (200 mg or 400 mg every other week) plus methotrexate or placebo plus methotrexate. ACR hybrid scores were compared with ACR20/50/70 outcomes.
Differences between active treatment and placebo were significant throughout the study using the ACR20 and ACR hybrid outcomes. In the certolizumab pegol 200 mg group, the median ACR hybrid score at week 52 (last observation carried forward) was 49.99. A total of 258 (65.8%) of 392 and 172 (43.9%) of 392 patients had ACR20 and ACR50 responses, respectively. An additional 55 patients (14.0%) and 59 patients (15.1%) had mean improvements in ACR core measures of ≥ 20% and ≥ 50%, respectively, and therefore had positive ACR hybrid scores, despite lacking ACR20 and ACR50 responses, respectively. In the placebo group, median ACR hybrid scores were <10 at most time points; unlike other measures, the ACR hybrid measure indicated worsening scores for many patients.
ACR hybrid analysis had greater sensitivity than traditional ACR20/50/70 criteria, demonstrating improvements in ACR20 nonresponders treated with certolizumab pegol. Negligible benefit was observed with placebo using ACR hybrid analysis.