title: Comparison of EuroQol-5D and short form-6D utility scores in multiethnic Asian patients with psoriatic arthritis: a cross-sectional study.
abstract: OBJECTIVE
  To compare EuroQol-5D (EQ-5D) and Short Form-6D (SF-6D) utility scores in multiethnic Asian patients with psoriatic arthritis (PsA).
  
  
  METHODS
  Consecutive patients fulfilling the Classification Criteria for Psoriatic Arthritis attending a rheumatology outpatient clinic were recruited and completed the EQ-5D and SF-6D questionnaires. Comparisons were performed by score distribution, mean, median, and the Outcome Measures in Rheumatology filter: i.e., truth, discrimination, and feasibility.
  
  
  RESULTS
  Eighty-six patients were enrolled (69 English-speaking and 17 Chinese-speaking; male:female ratio 0.91). The score distribution of SF-6D was normal, while that of EQ-5D was bimodal. A ceiling effect was observed in 20% of patients for EQ-5D and none for SF-6D. There were moderate correlations (Spearman's rho = 0.59, p < 0.0001) between the 2 scores, but poor agreements on scatterplot, intraclass correlation (ICC 0.43 and standardized ICC 0.21), and Bland-Altman plots. EQ-5D generated lower utility scores than SF-6D in the poorer health subgroup. SF-6D had stronger correlation with the general health status and other external measures of health; and it distinguished better between good and poor general health status, with better effect size and relative efficiency statistics. EQ-5D demonstrated higher patient acceptability.
  
  
  CONCLUSIONS
  EQ-5D and SF-6D instruments generated different utility scores in PsA. SF-6D may be superior because of normal scaling distribution and the absence of ceiling and floor effects. SF-6D also had better construct validity and better discrimination of poor health status. More studies are required for cost-utility analysis in PsA.
authors.affiliation: Department of Rheumatology and Immunology, Singapore General Hospital, Singapore. katyccc@hotmail.com
authors.forename: Ying-Ying
authors.initials: YY
authors.lastname: Leung
authors.forename: May-Ee
authors.initials: ME
authors.lastname: Png
authors.forename: Hwee-Lin
authors.initials: HL
authors.lastname: Wee
authors.forename: Julian
authors.initials: J
authors.lastname: Thumboo
mesh_terms: D000328:Adult; D000368:Aged; D015535:Arthritis, Psoriatic / Q000175:diagnosis* / Q000191:economics; D044466:Asian People; D003362:Cost-Benefit Analysis; D003430:Cross-Sectional Studies; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D010808:Physical Examination / Q000191:economics / Q000379:methods*; D011594:Psychometrics; D011788:Quality of Life; D019057:Quality-Adjusted Life Years; D011795:Surveys and Questionnaires
keywords: COMPARATIVE STUDY; COST BENEFIT; PSORIATIC ARTHRITIS; QUALITY-ADJUSTED LIFE-YEAR