title: The classification systems of the EQ-5D, the HUI II and the SF-6D: what do they have in common?
abstract: OBJECTIVE
  EQ-5D, HUI II and SF-6D often produce very different valuations for the same health state. This paper aims at clarifying to what extent this might be caused by differences between the multi-attribute classification systems belonging to these instruments.
  
  
  METHODS
  Subjects were 264 patients of rehabilitation clinics in Mecklenburg-Western Pomerania (44.3% female; mean age 49.1) who completed the EQ-5D, the HUI II and the SF-36 (the basis of the SF-6D). After scaling with principal component analyses for categorical data, each attribute of each classification system was regressed on the classification systems of the other two instruments, and all attributes together were subjected to ordinary principal component analysis with varimax rotation.
  
  
  RESULTS
  Adjusted multiple R(2) for regression analyses ranged from 0.01 to 0.57. The HUI II attribute 'sensation' and the SF-6D attribute 'role limitation' are virtually unrelated to the remainder. All other attributes of all three instruments can be predicted by each other. EQ-5D and HUI II focus distinctly more on physical functioning than SF-6D.
  
  
  CONCLUSIONS
  Although all three classification systems have a lot in common, they differ so much that EQ-5D, HUI II and SF-6D would produce different valuations even if these valuations were determined according to the same principle.
authors.affiliation: Trimberg Research Academy, University of Bamberg, c/o Kapuziner Strasse 16, 96047, Bamberg, Germany. uwe.konerding@uni-bamberg.de
authors.forename: Uwe
authors.initials: U
authors.lastname: Konerding
authors.forename: Jörn
authors.initials: J
authors.lastname: Moock
authors.forename: Thomas
authors.initials: T
authors.lastname: Kohlmann
mesh_terms: D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D012047:Rehabilitation Centers; D011795:Surveys and Questionnaires / Q000592:standards*