Validation of rheumatoid arthritis improvement criteria that include simplified joint counts.

To study the validity of response criteria for rheumatoid arthritis (RA) that included 28-joint counts instead of more comprehensive joint counts. In a double-blind, placebo-controlled trial of 105 patients treated with methotrexate, sulfasalazine, or both, response was evaluated at week 52. Both European League Against Rheumatism and American College of Rheumatology definitions of response, with comprehensive as well as simplified joint counts, were calculated. We studied the differences between the criteria with and without simplified joint counts, the discriminating capacity between treatment groups, and the association with change in functional capacity and joint damage. Response criteria that included 28-joint counts classified patients' responses more conservatively. No differences between treatment groups were found with either set of response criteria. The association with change in functional capacity was significant in all cases. All response criteria were significantly associated with radiographic progression of RA. Improvement criteria that include 28-joint counts are as valid as the original improvement criteria that included more comprehensive joint counts.