A uniform time trade off method for states better and worse than dead: feasibility study of the ‘lead time’ approach

Abstract

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.

Preparatory study for the revaluation of the EQ-5D tariff: methodology report

“…Traditionally, this has been regarded as unacceptable and arbitrary transformations have been applied. 3,[14][15][16] Under the established convention, H is calculated as −X/10.…”

“…[16][17][18] The following problems were identified with this procedure: (1) The method is not the same as the method for states better than dead; (2) time spent in health state H has become the decision variable, with the result that respondents are not valuing a specified time in the state (as is the case for states better than dead); and (3) the raw result is non-linear for the time spent in state H, such that as H approaches zero the index approaches negative infinity ( Figure 1) and, as is pointed out above, transformations used are arbitrary, and render the values incommensurable with those for states better than dead. The lead time -time trade-off (LT-TTO) was devised to overcome these problems.…”

“…Note first that the value of living in H for 1 year is given by X/10, regardless of whether H is better or worse than dead, and, second, the calculation assumes that the size of T is unaffected by the addition of the lead time. 16 As can be seen, a lead time of 15 years against a duration of 10 years will allow LT-TTO to elicit values in the range [−1.5 to 1]. If the value of H is < −1.5 then a respondent will strongly prefer immediate death over the prospect of 15 years of lead time plus 10 years in state H. This is called 'exhausting' the lead time, and if the objective is to identify a point of indifference for all states for all respondents, it calls for a longer lead time (or a shorter duration).…”

An exploration of the non‐iterative time trade‐off method to value health states

“…DCE TTO does not require a separate protocol or transformation but has its challenges (see above). The addition of lead time has been suggested as an alternative way of valuing both kinds of states using a uniform protocol (Devlin, Tsuchiya, Buckingham, & Tilling, 2011). This, in effect, allows the shorter duration in full health to take negative values and requires no arbitrary transformation of data.…”

“…This, in effect, allows the shorter duration in full health to take negative values and requires no arbitrary transformation of data. However, respondents may “exhaust” lead time (Devlin et al, 2011; Devlin et al, 2013), where a given lead time is not long enough to accommodate their preference for a state worse than dead. For example, if a respondent prefers to die immediately rather than to live in full health for 10 years (lead time) followed by 10 years in a severe state, then lead time TTO cannot determine an indifference point, only that the health state value is strictly lower than −1.…”