title: Do English and Chinese EQ-5D versions demonstrate measurement equivalence? An exploratory study.
abstract: BACKGROUND
  Although multiple language versions of health-related quality of life instruments are often used interchangeably in clinical research, the measurement equivalence of these versions (especially using alphabet vs pictogram-based languages) has rarely been assessed. We therefore investigated the measurement equivalence of English and Chinese versions of the EQ-5D, a widely used utility-based outcome instrument.
  
  
  METHODS
  In a cross-sectional study, either EQ-5D version was administered to consecutive outpatients with rheumatic diseases. Measurement equivalence of EQ-5D item responses and utility and visual analog scale (EQ-VAS) scores between these versions was assessed using multiple regression models (with and without adjusting for potential confounding variables), by comparing the 95% confidence interval (95%CI) of score differences between these versions with pre-defined equivalence margins. An equivalence margin defined a magnitude of score differences (10% and 5% of entire score ranges for item responses and utility/EQ-VAS scores, respectively) which was felt to be clinically unimportant.
  
  
  RESULTS
  Sixty-six subjects completed the English and 48 subjects the Chinese EQ-5D. The 95%CI of the score differences between these versions overlapped with but did not fall completely within pre-defined equivalence margins for 4 EQ-5D items, utility and EQ-VAS scores. For example, the 95%CI of the adjusted score difference between these EQ-5D versions was -0.14 to +0.03 points for utility scores and -11.6 to +3.3 points for EQ-VAS scores (equivalence margins of -0.05 to +0.05 and -5.0 to +5.0 respectively).
  
  
  CONCLUSIONS
  These data provide promising evidence for the measurement equivalence of English and Chinese EQ-5D versions.
authors.affiliation: Department of Medicine, National University of Singapore, Singapore. scip9152@nus.edu.sg
authors.forename: Nan
authors.initials: N
authors.lastname: Luo
authors.forename: Ling-Huo
authors.initials: LH
authors.lastname: Chew
authors.forename: Kok-Yong
authors.initials: KY
authors.lastname: Fong
authors.forename: Dow-Rhoon
authors.initials: DR
authors.lastname: Koh
authors.forename: Swee-Cheng
authors.initials: SC
authors.lastname: Ng
authors.forename: Kam-Hon
authors.initials: KH
authors.lastname: Yoon
authors.forename: Sheila
authors.initials: S
authors.lastname: Vasoo
authors.forename: Shu-Chuen
authors.initials: SC
authors.lastname: Li
authors.forename: Julian
authors.initials: J
authors.lastname: Thumboo
mesh_terms: D000328:Adult; D002681:China; D003430:Cross-Sectional Studies; D005260:Female; D006304:Health Status; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D011594:Psychometrics / Q000295:instrumentation*; D011788:Quality of Life; D012044:Regression Analysis; D012216:Rheumatic Diseases / Q000523:psychology*; D012923:Social Class; D011795:Surveys and Questionnaires / Q000592:standards; D014177:Translations