title: Protocols for time tradeoff valuations of health states worse than dead: a literature review.
abstract: BACKGROUND
  The time tradeoff (TTO) method of preference elicitation allows respondents to value a state as worse than dead, generally either through the Torrance protocol or the Measurement and Valuation of Health (MVH) protocol. Both of these protocols have significant weaknesses: Valuations for states worse than dead (SWD) are elicited through procedures different from those for states better than dead (SBD), and negative values can be extremely negative.
  
  
  OBJECTIVE
  To provide an account of the different TTO designs for SWD, to identify any alternatives to the MVH and Torrance approaches, and to consider the merits of the approaches identified.
  
  
  METHODS
  Medline was searched to identify all health state valuation studies employing TTO. The ways in which SWD were handled were recorded. Furthermore, to ensure that there are no unpublished but feasible TTO variants, the authors developed a theoretical framework for identifying all potential variants.
  
  
  RESULTS
  The search produced 593 hits, of which 218 were excluded. Of the remaining 375 articles, only 29 included protocols for SWD. Of these, 23 used the MVH protocol and 4 used the Torrance protocol. The other 2 used 1 protocol for SBD and SWD, one making use of lead time and the other using a 2-stage procedure with chaining. The systematic framework did not identify any alternatives to the Torrance and MVH protocols that were superior to the lead time approach.
  
  
  CONCLUSIONS
  Few studies elicit values for SWD. The lead time approach is a potential alternative to the Torrance and MVH protocols. Key words: QALY; states worse than dead; health state valuation; preference elicitation.
authors.affiliation: School of Health and Related Research, University of Sheffield, UK. c.tilling@sheffield.ac.uk
authors.forename: Carl
authors.initials: C
authors.lastname: Tilling
authors.forename: Nancy
authors.initials: N
authors.lastname: Devlin
authors.forename: Aki
authors.initials: A
authors.lastname: Tsuchiya
authors.forename: Ken
authors.initials: K
authors.lastname: Buckingham
mesh_terms: D001294:Attitude to Health; D006304:Health Status; D006801:Humans; D057240:Patient Preference / Q000523:psychology*; D011788:Quality of Life; D013997:Time Factors