Identification of disease activity and health status cut-off points for the symptom state acceptable to patients with rheumatoid arthritis

Abstract

Background: Established thresholds for low levels of disease activity need to be examined from a patients' perspective.

Objective: To identify new cut-off points for patients' perception of satisfactory condition (patient acceptable symptom state (PASS)) in composite indices and patient-reported outcomes, and to examine the agreement between the new PASS cut-off points for composite indices and existing thresholds for remission, low and moderate disease activity.

Methods: Patients with rheumatoid arthritis from a treatment register (n = 1496, 72.1% women, mean (SD) age 53.9 (13.5) years, disease duration 7.6 (9.1) years, 28-joint Disease Activity Score (DAS28) 4.98 (1.36)) responded during follow-up (12, 24 and 52 weeks) to a global dichotomised question on satisfactory condition (PASS). New PASS cut-off points were identified with the 75th centile estimation and receiver operating characteristic analyses for a variety of outcome measures, and cut-off points for composite indices were examined for agreement with the low disease activity threshold (1.625) of the Patient Activity Scale (PAS) and thresholds for remission, low and moderate disease activity in DAS28, Simplified Disease Activity Index (SDAI) and Clinical Disease Activity Index (CDAI).

Results: New PASS cut-off points for DAS28, SDAI and CDAI were in the moderate range of disease activity, and the cut-off point was 3.56 for PAS. Agreement between thresholds for disease activity levels and the PASS cut-off points was best for low disease activity (accuracy 64.5-74.6), and better for moderate disease activity (accuracy 61.3-67.2) than for remission (accuracy 30.7-45.8).

Conclusion: The current PASS concept seems to be in the range of moderate disease activity.