Objectives To test the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) and disease activity score in 44 and 28 joints (DAS, DAS28) definitions of remission in early rheumatoid arthritis (RA), against disability and ultrasound-detectable synovitis.

Methods In an observational study of early RA patients, remission rates were determined and compared in 166 patients. The remission definitions included the simplified disease activity index (SDAI≤3.3), ACR/EULAR (categorical), DAS28 (<2.6) and DAS (<1.6). The health assessment questionnaire (HAQ) was completed at baseline and 12 months, power Doppler-positive synovitis (PDPS) was assessed at baseline, 6 and 12 months. Cross-sectionally, the outcomes were low functional disability (HAQ≤0.5) or absent PDPS in all joints, while longitudinally the outcomes were stable low functional disability and persistent absent PDPS in all joints.

Results At baseline, 33.7% of patients achieved DAS28 remission, 43.37% DAS remission, 16.8% SDAI remission, 13.8% ACR/EULAR remission. DAS28, SDAI and ACR/EULAR remission was cross-sectionally associated with low functional disability and absent PDPS. All definitions were longitudinally associated with low functional disability: positive likelihood ratios (LR+) of 3.24 for DAS28, 2.14 for DAS, 4.86 for SDAI, 5.67 for ACR/EULAR criteria, and with absent PDPS for DAS28 (LR+ 1.66), SDAI (LR+ 6.46), ACR/EULAR (LR+ 5.07).

Conclusions The new remission definitions confirmed their validity in an observational setting and identify patients with better disease control.