title: The effects of lead time and visual aids in TTO valuation: a study of the EQ-VT framework.
abstract: BACKGROUND
  The effect of lead time in time trade-off (TTO) valuation is not well understood. The purpose of this study was to investigate the effects on health-state valuation of the length of lead time and the way the lead-time TTO task is displayed visually.
  
  
  METHODS
  Using two general population samples, we compared three lead-time TTO variants: 10 years of lead time in full health preceding 5 years of unhealthy time (standard); 5 years of lead time preceding 5 years of unhealthy time (experimental); and 10 years of lead time and 5 years of unhealthy time, presented with a visual aid to highlight the point where the lead time ends (experimental). Participants were randomized to receive one of the lead-time variants, as administered by a computer software program.
  
  
  RESULTS
  Health-state values generated by TTO valuation tasks using a longer lead time were slightly lower than those generated by tasks using a shorter lead time. When lead time and unhealthy time were presented with visual aids highlighting the difference between the lead time and unhealthy time, respondents spent more time considering health states with a value close to 0.
  
  
  CONCLUSIONS
  Different lead-time time trade-off variants should be carefully studied in order to achieve the best measurement of health-state values using this new method.
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, 16 Medical Drive, Block MD3, Singapore 117597, Singapore. nan_luo@nuhs.edu.sg
authors.forename: Nan
authors.initials: N
authors.lastname: Luo
authors.forename: Minghui
authors.initials: M
authors.lastname: Li
authors.forename: Elly A
authors.initials: EA
authors.lastname: Stolk
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Devlin
mesh_terms: D000328:Adult; D001296:Audiovisual Aids; D002681:China; D004522:Educational Status; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D010865:Pilot Projects; D011788:Quality of Life / Q000523:psychology*; D012846:Singapore; D011795:Surveys and Questionnaires; D013997:Time Factors; D026712:Value of Life
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