title: The disease activity score is not suitable as the sole criterion for initiation and evaluation of anti-tumor necrosis factor therapy in the clinic: discordance between assessment measures and limitations in questionnaire use for regulatory purposes.
abstract: OBJECTIVE
  The Disease Activity Score (DAS) is widely used in clinical trials. A DAS of 5.1 defines the level of severe rheumatoid arthritis (RA) and is the criterion for the initiation of anti-tumor necrosis factor therapy in the UK and The Netherlands. In North America, similar rules are sometimes imposed. However, it is not known how accurately the DAS characterizes RA activity. The present study was undertaken to determine the concordance between DAS scores and physicians' assessments of RA activity, to investigate factors relating to discrepancies, and to assess the suitability of using the DAS in individual patients.
  
  
  METHODS
  Six hundred sixty-nine RA patients were assessed using the DAS and other clinical measures. A physician's global estimate of RA activity was performed using an 11-point predefined scale and a standard definition of disease activity.
  
  
  RESULTS
  The DAS and physician global assessment had substantially different distributions of values. The level of agreement (Kendall's tau-a) between DAS scores and physician global assessments was 49% (95% confidence interval 45-53%), Lin's coefficient of concordance was 0.62, and the Bland-Altman 95% limits of agreement were -3.17 and 3.99. These results suggest poor-to-moderate concordance between the 2 measures of disease activity.
  
  
  CONCLUSIONS
  The DAS and the physician's assessment of RA activity do not approach, value, and weight RA variables to the same extent, suggesting that RA activity is not evaluated similarly by North American physicians and with the DAS. The scales do not have acceptable levels of concordance. There is too much inherent variability in the DAS and other RA scales (e.g., the Health Assessment Questionnaire) to recommend them as sole determinants of RA activity for clinical or regulatory purposes.
authors.affiliation: National Data Bank for Rheumatic Diseases, Wichita, Kansas 67214, USA. fwolfe@arthritis-research.org
authors.forename: Frederick
authors.initials: F
authors.lastname: Wolfe
authors.forename: Kaleb
authors.initials: K
authors.lastname: Michaud
authors.forename: Theodore
authors.initials: T
authors.lastname: Pincus
authors.forename: Daniel
authors.initials: D
authors.lastname: Furst
authors.forename: Edward
authors.initials: E
authors.lastname: Keystone
mesh_terms: D000328:Adult; D000368:Aged; D000554:Ambulatory Care Facilities; D018501:Antirheumatic Agents / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy* / Q000276:immunology / Q000503:physiopathology*; D002170:Canada; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012219:Rheumatology / Q000379:methods* / Q000592:standards; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors*; D014481:United States
chemical_list: D018501:Antirheumatic Agents; D014409:Tumor Necrosis Factor-alpha