Active foot synovitis in patients with rheumatoid arthritis: applying clinical criteria for disease activity and remission may result in underestimation of foot joint involvement

OBJECTIVE: To determine whether application of criteria for remission in rheumatoid arthritis (RA) may result in underestimation of foot joint involvement among patients in a clinic setting. METHODS: RA patients (n _ 123) were assessed at baseline and 6 months after commencement of a response-driven combination disease-modifying antirheumatic drug (DMARD) protocol. Remission was assessed using disease activity measures (the 28-joint Disease Activity Score using the erythrocyte sedimentation rate [DAS28-ESR], Simplified Disease Activity Index [SDAI], and Clinical Disease Activity Index [CDAI]) as well as Boolean-based criteria for remission (the 1981 American College of Rheumatology [ACR] preliminary criteria and the 2011 ACR/European League Against Rheumatism [EULAR] provisional criteria). The prevalence of foot synovitis and the mean swollen/tender foot joint count in RA patients meeting any of these remission criteria were estimated by hurdle (mixed distribution) regression. RESULTS: In patients who received 6 months of combination DMARD treatment, application of the 1981 ACR criteria and the newly proposed 2011 ACR/EULAR criteria, each utilizing full joint counts (which includes assessment of the feet), classified the least number of patients as being in remission (8–10%), and evidence of foot synovitis was minimal among these patients. In contrast, ongoing foot synovitis was present in a substantial proportion of patients (>20%) meeting the 28-joint count criteria for remission, including the DAS28-ESR, SDAI, CDAI, and 2011 ACR/EULAR criteria (clinical practice setting or clinical trials). Furthermore, applying the 2011 ACR/EULAR composite remission criterion of a SDAI score