Defining criteria for rheumatoid arthritis patient-derived disease activity score that correspond to Disease Activity Score 28 and Clinical Disease Activity Index based disease states and response criteria.

Objective: Two versions of a patient-based DAS (PDAS) 1 and 2 (with and without ESR) have been developed and validated in RA. The objective of this study was to define PDAS1- and PDAS2-based criteria for remission, low, moderate and high disease activity and responses to treatment.

Method: Using receiver operating characteristic curves, the optimal thresholds for PDAS1 and PDAS2 that correspond to validated assessor-based DAS (DAS28) and Clinical Disease Activity Index (CDAI) disease statuses were determined. Data from RA patients initiated on disease-modifying drugs were used to determine optimal thresholds for PDAS1 and PDAS2 that corresponded to EULAR good and moderate responses. Agreement with DAS28, CDAI and EULAR response criteria was assessed by Cohen's κ statistic.

Results: Threshold for PDAS1 and PDAS2 demonstrated fair to moderate agreement with DAS28 [κ = 0.44 (95% CI: 0.40, 0.50) and 0.31 (95% CI: 0.25, 0.38)] and CDAI [κ = 0.27 (95% CI: 0.22, 0.33) and 0.42 (95% CI: 0.35, 0.49)] disease statuses, respectively, which was similar to agreement between DAS28 and CDAI [κ = 0.54 (95% CI: 0.46, 0.61)] within this group. Agreement of EULAR good and moderate response with PDAS1 and PDAS2 was κ = 0.46 (95% CI: 0.27, 0.64) and 0.38 (95% CI: 0.20, 0.56), respectively.

Conclusion: Thresholds for disease activity statuses and response to treatment for PDAS1 and PDAS2 have been established. They have comparable agreement to assessor-based criteria.