title: Rationale and strategies for reevaluating the ACR20.
abstract: OBJECTIVE
  To assess whether the American College of Rheumatology response criteria ACR20 should be replaced by another definition of response with enhanced discriminant validity.
  
  
  METHODS
  We worked with statisticians to define over 100 different ways of defining response, including dichotomous definitions (e.g., ACR20; ACR50; ACR70; low disease activity), ordinal definitions (EULAR response; ACR20, ACR50, ACR70), disease activity indexes [Disease Activity Score (DAS); Disease Activity Index, SDAI], continuous definitions (mean percentage improvement in all core set measures; nACR, ACRn), and hybrid definitions (ACR20, ACR50, ACR70 defined for a patient as 0, 1, 2, 3 scale with continuous measures between intervals) along with variations on each of these approaches (e.g., percentage vs absolute change in DAS; e.g., measures requiring vs not requiring joint count improvement). To test clinical validity, we administered a survey using patients from a trial who had various levels of improvement and asked rheumatologists whether and by how much these patients improved. For Sn-to-Chge, we are collecting data from large disease modifying antirheumatic drug multicenter trials in rheumatoid arthritis and ranking candidate definitions of response on their average p values in distinguishing active treatment from placebo or combination compared to single comparator.
  
  
  RESULTS
  We surveyed 52 rheumatologists about which trial patients had improved and by how much. Trial data were obtained and tested for sensitivity to change.
  
  
  CONCLUSIONS
  A rigorous data-driven consensus process was used to reassess the ACR20.
authors.affiliation: Boston University School of Medicine, Boston, Massachusetts 02118, USA. dfelson@bu.edu
authors.forename: David T
authors.initials: DT
authors.lastname: Felson
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Furst
authors.forename: Maarten
authors.initials: M
authors.lastname: Boers
mesh_terms: D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy*; D002986:Clinical Trials as Topic / Q000379:methods* / Q000592:standards / Q000706:statistics & numerical data; D032921:Consensus; D023381:Endpoint Determination / Q000379:methods* / Q000706:statistics & numerical data; D006304:Health Status; D006801:Humans; D017063:Outcome Assessment, Health Care / Q000379:methods* / Q000706:statistics & numerical data; D012720:Severity of Illness Index; D012955:Societies, Medical / Q000592:standards; D016896:Treatment Outcome