title: Individual differences in the use of the response scale determine valuations of hypothetical health states: an empirical study.
abstract: BACKGROUND
  The effects of socio-demographic characteristics of the respondent, including age, on valuation scores of hypothetical health states remain inconclusive. Therefore, we analyzed data from a study designed to discriminate between the effects of respondents' age and time preference on valuations of health states to gain insight in the contribution of individual response patterns to the variance in valuation scores.
  
  
  METHODS
  A total of 212 respondents from three age groups valued the same six hypothetical health states using three different methods: a Visual Analogue Scale (VAS) and two variants of the Time trade-off (TTO). Analyses included a generalizability study, principal components analysis, and cluster analysis.
  
  
  RESULTS
  Valuation scores differed significantly, but not systematically, between valuation methods. A total of 36.8% of variance was explained by health states, 1.6% by the elicitation method, and 0.2% by age group. Individual differences in the use of the response scales (e.g. a tendency to give either high or low TTO scores, or a high or low scoring tendency on the VAS) were the main source of remaining variance. These response patterns were not related to age or other identifiable respondent characteristics.
  
  
  CONCLUSIONS
  Individual response patterns in this study were more important determinants of TTO or VAS valuations of health states than age or other respondent characteristics measured. Further valuation research should focus on explaining individual response patterns as a possible key to understanding the determinants of health state valuations.
authors.affiliation: Department of Public Health, Erasmus MC/University Medical Center Rotterdam, Rotterdam, The Netherlands. m.essink-bot@erasmusmc.nl
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: Essink-Bot
authors.forename: Marja C
authors.initials: MC
authors.lastname: Stuifbergen
authors.forename: Willem-Jan
authors.initials: WJ
authors.lastname: Meerding
authors.forename: Caspar W N
authors.initials: CW
authors.lastname: Looman
authors.forename: Gouke J
authors.initials: GJ
authors.lastname: Bonsel
mesh_terms: D000328:Adult; D000367:Age Factors; D001294:Attitude to Health; D005260:Female; D006304:Health Status; D006801:Humans; D008017:Life Expectancy; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D011788:Quality of Life; D019057:Quality-Adjusted Life Years; D018570:Risk Assessment; D012945:Social Values; D011795:Surveys and Questionnaires; D013997:Time Factors; D026712:Value of Life