A Proposal to Standardize Low Disease Activity Criteria in Rheumatoid Arthritis Based on the Outcome Measures in Rheumatology Minimal Disease Activity Definition

OBJECTIVE: We aimed to standardize the definition of low disease activity in rheumatoid arthritis (RA) using the Outcome Measures in Rheumatology (OMERACT) group's proposed definition of minimal disease activity. METHOD: Based on a nationwide RA database, we proposed new Boolean low disease activity criteria using OMERACT's core set definition of minimal disease activity that requires the fulfillment of at least five of the following seven core set measures: a pain score of 2 or less, a swollen joint count (SJC28) of 1 or fewer, a tender joint count of 1 or fewer, a Health Assessment Questionnaire score of 0.5 or less, a Physician's Global Assessment score of 1.5 or less, a Patient's Global Assessment score of 2 or less, and an erythrocyte sedimentation rate (ESR) of 20 mm/h or less. Using receiver operating characteristic analysis, we determined the cutoffs for the Simplified Disease Activity Index (SDAI), Clinical Disease Activity Index (CDAI), Routine Assessment of Patient Index Data 3 (RAPID3), and the Disease Activity Score in 28 joints (DAS28)–ESR. RESULTS: Of 8298 patients, 56.2% met the proposed Boolean low disease activity criteria. We determined an SDAI score of 5.5 or less and a CDAI score of 5 or less to be the new cutoffs, and we chose a DAS28 of 2.85 or less (the original cutoff for DAS‐based minimal disease activity) and a RAPID3 score of 6 or less (the original cutoff for RAPID3‐based low disease activity) with or without a swollen joint count (SJC) (SJC of 2 or fewer) as the cutoffs for DAS28 and RAPID3. The agreement between the new cutoffs for DAS28 of 2.85 or less vs. CDAI score of 5 or less, CDAI score of 5 or less vs. RAPID3 score of 6 or less (with SJC of 2 or fewer), and DAS28 of 2.85 or less vs. RAPID3 score of 6 or less (with SJC of 2 or fewer), was 0.619, 0.612 (0.702), and 0.474 (0.531), respectively. CONCLUSION: OMERACT's minimal disease activity definition may be used to standardize the criteria for low disease activity.