title: Comparison of contemporaneous EQ-5D and SF-6D responses using scoring algorithms derived from similar valuation exercises.
abstract: OBJECTIVE
  Poor agreement between preference-based health-related quality-of-life instruments has been widely reported across patient and community-based samples. This study compares index scores generated from contemporaneous EQ-5D (3-level version) and SF-6D (SF-36 version) responses using scoring algorithms derived from independently-conducted Australian population-representative discrete choice experiments (DCEs), providing the first comparative analysis of health state valuations using the same method of valuation across the full value sets.
  
  
  METHODS
  EQ-5D and SF-6D responses from seven patient data sets were transformed into health state valuations using published DCE-derived scoring algorithms. The empirical comparative evaluation consisted of graphical illustration of the location and spread of index scores, reporting of basic descriptive statistics, exploration of between-measure differences in mean index scores, and analysis of agreement.
  
  
  RESULTS
  Compared with previously published findings regarding the comparability of "conventional" EQ-5D and SF-6D index scores, health state valuations from the DCE-derived scoring procedures showed that agreement between scores remained "fair" (intraclass correlation coefficient values across the seven data sets ranged from 0.375 to 0.615). Mean SF-6D scores were significantly lower than the respective mean EQ-5D score across all patient groups (mean difference for the whole sample = 0.253).
  
  
  CONCLUSIONS
  The magnitude of disagreement previously reported between EQ-5D and SF-6D index scores is not ameliorated through the application of DCE-derived value sets; sizeable discrepancies remain. These findings suggest that differences between EQ-5D and SF-6D index scores persist because of their respective descriptive systems. Further research is required to explore the implications of variations in the descriptive systems of preference-based instruments.
authors.affiliation: Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada; Centre for Clinical Epidemiology and Evaluation, Vancouver Coastal Health Research Institute, Vancouver, BC, Canada. Electronic address: david_whitehurst@sfu.ca.
authors.forename: David G T
authors.initials: DG
authors.lastname: Whitehurst
authors.affiliation: Centre for Health Economics Research and Evaluation, University of Technology Sydney, Sydney, Australia.
authors.forename: Richard
authors.initials: R
authors.lastname: Norman
authors.affiliation: Health Economics and Decision Science, School of Health and Related Research, University of Sheffield, Sheffield, UK.
authors.forename: John E
authors.initials: JE
authors.lastname: Brazier
authors.affiliation: Centre for Health Economics Research and Evaluation, University of Technology Sydney, Sydney, Australia.
authors.forename: Rosalie
authors.initials: R
authors.lastname: Viney
mesh_terms: D000465:Algorithms; D001315:Australia; D002755:Choice Behavior; D006304:Health Status; D006801:Humans; D057240:Patient Preference; D011788:Quality of Life; D019057:Quality-Adjusted Life Years; D011795:Surveys and Questionnaires
keywords: EQ-5D; SF-6D; comparative analysis; discrete choice experiment; standard gamble; time trade-off