title: 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.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  Thresholds for disease activity statuses and response to treatment for PDAS1 and PDAS2 have been established. They have comparable agreement to assessor-based criteria.
authors.affiliation: Department of Rheumatology, Queen Elizabeth Hospital, Kowloon, Hong Kong.
authors.forename: Alexander M H
authors.initials: AM
authors.lastname: Leung
authors.affiliation: Institute of Primary Care & Public Health, Cardiff University School of Medicine, Cardiff, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Farewell
authors.affiliation: LKS Faculty of Medicine and Queen Mary Hospital, The University of Hong Kong, Hong Kong.
authors.forename: Chak Sing
authors.initials: CS
authors.lastname: Lau
authors.affiliation: Section of Rheumatology, Institute of Infection and Immunity, Cardiff University School of Medicine, Cardiff, UK ChoyEH@cardiff.ac.uk.
authors.forename: Ernest H S
authors.initials: EH
authors.lastname: Choy
mesh_terms: D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000071066:Patient Reported Outcome Measures; D012372:ROC Curve; D012074:Remission Induction; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D016896:Treatment Outcome
chemical_list: D018501:Antirheumatic Agents
keywords: DAS; PDAS; disease activity; patient reported outcome measure (PROM); rheumatoid arthritis