Brief report: rheumatoid arthritis response criteria and patient-reported improvement in arthritis activity: is an American College of Rheumatology twenty percent response meaningful to patients?

Objective: To examine the association of the American College of Rheumatology (ACR) response criteria (20% improvement [ACR20], ACR50, and ACR70) and the European League Against Rheumatism (EULAR) response criteria with patient-reported improvement in rheumatoid arthritis (RA) activity.

Methods: Two hundred fifty patients with active RA were studied prospectively, before and after escalation of antirheumatic treatment. Patients were asked to report if they subjectively judged that they had experienced important improvement with treatment, and the proportion of patients who reported improvement was compared with the proportion who met the ACR20, ACR50, ACR70, and EULAR response criteria.

Results: Improvement in overall arthritis status was reported by 167 patients (66.8%), while 107 patients (42.8%) had an ACR20 response, 52 (20.8%) had an ACR50 response, 24 (9.6%) had an ACR70 response, and 136 (54.4%) had a EULAR moderate/good response. ACR20 response had a sensitivity of 0.57 and a specificity of 0.85 for clinically important improvement as judged by patients. Sensitivities of the ACR50, ACR70, and EULAR moderate/good responses were 0.30, 0.14, and 0.68, respectively, while their specificities were 0.97, 0.99, and 0.73, respectively. The ACR hybrid score with the highest sensitivity and specificity for important improvement was 19.99.

Conclusion: Among patients with active RA, ACR20 responses are highly specific measures of improvement as judged by patients, but exclude a substantial proportion of patients who consider themselves improved. Response criteria are associated with, but not equivalent to, patient-perceived improvement.