[A new approach to assessing rheumatoid arthritis (RA) disease activity using the American College of Rheumatology core set of disease activity measures for RA trials--a multi-center study].

To characterize the American College of Rheumatology core set of disease activity measures for rheumatoid arthritis (RA) clinical trials (ACR core set measures) and the ACR definition of improvement of RA (ACR improvement definition), we studied 42 Japanese patients with active RA who were treated with DMARDs including mizoribine. Each patient's disease activity was assessed at the time of enrollment to the study and after 24 weeks using the ACR core set measures as well as the physical global assessment through the conventional measures. Twenty-five (60%) patients were discerned as showing improved by physicians through the conventional measures. This decision appeared to be based on improvement in Lansbury activity index (LAI) and C-reactive protein (CRP) value. Twelve of the 25 "improved" patients satisfied the ACR improvement definition. The 12 patients showed significant improvement in "outcome" measures including patients assessments of pain, disease activity, and physical function, compared to the 30 patients not satisfying the ACR definition. However, no significant differences were observed between these two groups in "process" measures including LAI, tender joint count, swallen joint count, or CRP value. In conclusion, the ACR core set measures including both process and outcome measures have potential to reflect clinical important changes on "real life" of patients with RA.