title: Self-valuation and societal valuations of health state differ with disease severity in chronic and disabling conditions.
abstract: OBJECTIVE
  We sought to determine the relationship between self-reported ratings of health-related quality of life (HRQoL) by people with 3 chronic and disabling conditions and population estimates of those health states and to model factors that might explain the disagreement between these 2 ratings.
  
  
  METHODS
  A cross-sectional postal survey was sent in which each participant completed a set of questionnaires addressing HRQoL. Data from self-valuation on a visual analog scale (VAS) was compared with a population-based VAS-equivalent valuation, using the EQ-5D instrument. Different ways of scaling the 2 VAS scores were also explored. Data were analyzed using descriptive statistics and analysis of covariance.
  
  
  METHODS
  A community sample of 1036 people took part in the study (rheumatoid arthritis n = 142, stroke n = 585, multiple sclerosis n = 309). MEASUREMENT INSTRUMENT: The EQ-5D health state profile and accompanying visual analog scale were used.
  
  
  RESULTS
  Self-ratings were significantly different than the population-based ratings, and agreement was poor, both on the original scale of the data and by analyses of rescaled data. On the original scales the mean difference was 0.13 (95% confidence interval 0.117-0.143). Diagnosis, health state severity, and its square explained 35.3% of the variation in the differences between self and population ratings with a curvilinear relationship suggesting that the differences increased as the health state worsened, but at a decreasing rate as health state severity increased.
  
  
  CONCLUSIONS
  This study provides evidence that EQ-5D population valuation estimates of treatment benefit for people with disabling and chronic conditions may well be inaccurate representations of the degree of change actually experienced by the individual with the condition. The varying magnitude of difference between the 2 forms of valuation has important implications for interpreting shifts in health status valuation following interventions for these populations.
authors.affiliation: Division of Rehabilitation and Occupation Studies, Auckland University of Technology, Auckland, New Zealand. Kathryn.McPherson@aut.ac.nz
authors.forename: Kathryn
authors.initials: K
authors.lastname: McPherson
authors.forename: Julie
authors.initials: J
authors.lastname: Myers
authors.forename: William J
authors.initials: WJ
authors.lastname: Taylor
authors.forename: Harry K
authors.initials: HK
authors.lastname: McNaughton
authors.forename: Mark
authors.initials: M
authors.lastname: Weatherall
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000453:epidemiology / Q000503:physiopathology* / Q000523:psychology; D001294:Attitude to Health; D002908:Chronic Disease / Q000453:epidemiology / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000453:epidemiology / Q000503:physiopathology* / Q000523:psychology; D009520:New Zealand / Q000453:epidemiology; D011788:Quality of Life / Q000523:psychology*; D012649:Self Concept; D012720:Severity of Illness Index; D018434:Sickness Impact Profile; D012938:Social Perception; D012945:Social Values; D020521:Stroke / Q000453:epidemiology / Q000503:physiopathology* / Q000523:psychology