A uniform Time Trade Off method for states better and worse than dead: feasibility study of the 'lead time' approach SummaryThe way Time Trade Off (TTO) values are elicited for states of health considered 'worse than being dead' has important implications for the mean values used in economic evaluation. Conventional approaches to TTO, as used in the UK's 'MVH' value set, are problematic because they require fundamentally different tradeoffs tasks for the valuation of states better and worse than dead. This study aims to refine and test the feasibility of a new approach described by Robinson and Spencer (2006), and to explore the characteristics of the valuation data it generates. The approach introduces a 'lead time' into the TTO, producing a uniform procedure for generating values either >0 or <0. We used this lead time TTO to value 10 moderate to severe EQ-5D states using a sample of the general public (n=109). We conclude that the approach is feasible for use in valuation studies, and appears to overcome the discontinuity in values around 0 evident in conventional methods.

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.

Seven empirical studies were identified. Overall, it seems that not explicitly mentioning the inclusion of income will induce a minority of respondents to include these effects and this appears not to influence results. More empirical work is needed, using generic instruments, larger samples, and using the interview method of administration.

'Lead Time' TTO improves upon conventional TTO by providing a uniform method for eliciting positive and negative values. This research investigates (i) the values generated from different combinations of time in poor health and in full health; and the order in which these appear (lead vs. lag); (ii) whether values concur with participants' views about states; (iii) methods for handling extreme preferences. n = 208 participants valued five EQ-5D states, using two of four variants. Combinations of lead time and health state duration were: 10 years and 20 years; 5 years and 1 year; 5 years and 10 years; and a health state duration of 5 years with a lag time of 10 years. Longer lead times capture more preferences, but may involve a framing effect. Lag time results in less non-trading for mild states, and less time being traded for severe states. Negative values broadly agree with participants' stated opinion that the state is worse than dead. The values are sensitive to the ratio of lead time to duration of poor health, and the order in which these appear (lead vs. lag). It is feasible to handle extreme preferences though challenges remain.

Background: The estimation of Quality Adjusted Life Years gained from treatment requires length of life to be quality adjusted by the weight ('value') attached to the quality of life in each health state. These weights are anchored on a scale of 1 for full health and 0 for dead, with health states considered to be so bad that they are worse than being dead, having negative values. A widely used method for obtaining these values is the 'Time Trade Off' (TTO). The National Institute for Health and Clinical Excellence (NICE), for example, recommend the use of TTO values in evidence submitted to it on the cost effectiveness of new technologies. However, there are some important problems with TTO. These problems centre on the inability of the method adequately to handle very poor states of health, which people may consider to be worse than dead. Where that arises, the TTO has to switch to a different questioning process, with corresponding problems for the comparability and interpretation of values in the negative range. In previous research, we tested a new TTO approach, the 'Lead Time TTO', which is capable of producing weights both for states better and worse than dead in a uniform manner. Aims: The aims of this research are (i) to investigate the values generated from Lead Time TTO (LT-TTO) using different combinations of the duration of the health state and the time in full health which participants are asked to consider; as well as varying the order in which these appear (Lag Time TTO); (ii) to gauge if values generated from these methods concur with participants' views as to whether the states are better or worse than dead (iii) to explore a range of methods for handling the preferences of those whose distaste for very poor health states is such that they 'use up' all their lead time. Methods: A sample of 200 members of the general public valued five health states, using two of four variants of the LT-TTO: a lead time of 10 years with a health state duration of 20 years; a lead time of 5 years and a health state duration of 1 year; a lead time of 5 years and a duration of 10 years; and a duration of 5 years with a lag time of 10 years. Participants also responded to a range of supplementary tasks and other questions. Results: Values are influenced by the length of the lead time relative to the health state duration. Longer lead times enable somewhat more preferences to be captured, but appear to exert a framing effect on values. Lag time TTO results in less non-trading for mild states, and to participants trading off less time for severe states. Of those who valued the worst health state as negative, 70% also expressed the view that this state was worse than dead. Conclusions: LT-TTO confers an important advantage over the traditional TTO by providing a single method capable of generating positive and negative values that seem broadly in keeping with participants' stated views about those states being better or worse than dead. However, values are sensitive to the length of time in full health relative to the d...