New Definition for Low Disease Activity in RA May Standardize Criteria Among Disease Activity Scores

New 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) erythrocyte sedimentation rate have been proposed to standardize the definition of low disease activity in patients with rheumatoid arthritis (RA). The new cutoffs were calculated based on the results of a cross-sectional study published in ACR Open Rheumatology.

The study included data from the Japanese multicenter observational NinJa database of patients with RA in the year 2015 (N=8298). In this study, the Boolean low disease activity criteria for RA was defined as achievement of ≥5 of the 7 core set measures, including a pain score of ≤2, a swollen joint count of ≤1, a tender joint count of ≤1, a Health Assessment Questionnaire (HAQ) score of ≤0.5, a physician global assessment score of ≤1.5, a patient global assessment score of ≤2, and an erythrocyte sedimentation rate of ≤20 mm/h.

Current cutoffs for DAS28-based minimal disease activity and low disease activity for DAS28, SDAI, CDAI, and RAPID3 were evaluated. A receiver operating characteristic curve analysis was performed for investigator-deemed inappropriate cutoffs to identify cutoffs for the proposed Boolean low disease activity criteria.

Approximately 56.2% of the NinJa patients in this study met the proposed criteria for Boolean low disease activity. New cutoffs for low disease activity scores included an SDAI score of ≤5.5 and a CDAI score of ≤5. A DAS28 of ≤2.85 and a RAPID3 score of ≤6 with or without a swollen joint count of ≤2 were also chosen as cutoff values.

Compared with the current cutoffs, the new cutoffs based on the Boolean low disease activity criteria showed better agreement among themselves. The agreement between the new cutoffs for a DAS28 of ≤2.85 vs a CDAI score of ≤5 was 0.619. Likewise, the agreement between a CDAI score of ≤5 vs a RAPID3 score of ≤6 with swollen joint count of ≤2 was 0.616, and the agreement between a DAS28 of ≤2.85 vs a RAPID3 score of ≤6 with swollen joint count of ≤2 was 0.474.

The investigators suggested these proposed cutoffs “…may be used for the cutoffs of low disease activity in routine clinical practice.”

However, the researchers noted that the patients included from the NinJa cohort had better-controlled disease than populations in other previous research, which may limit the results.

Reference

Yokogawa N, Shimada K, Sugii S, et al. A proposal to standardize low disease activity criteria in rheumatoid arthritis based on the outcome measures in rheumatology minimal disease activity definition [published online May 3, 2020]. ACR Open Rheumatol. doi:10.1002/acr2.11142