An Empirical Study of Two Alternative Comparators for Use in Time Trade-Off Studies.

BACKGROUND: Studies to produce value sets for preference-based measures of health require definition of a full health upper anchor if the values are to be used to calculate quality-adjusted life years. Recent value sets derived for the EQ-5D-5L instrument have described the upper anchor as "full health," whereas older valuation studies for the EQ-5D used "best health state" in the descriptive system (11111). It is unclear whether this change could have led to differences in the values obtained. The objective of this study was to assess differences in time trade-off (TTO) valuations using two different comparators (full health and 11111).

METHODS: Preferences for EQ-5D-5L health states were elicited from a broadly representative sample of the UK general public. TTO data were collected by using computer-assisted personal interviews. Respondents were randomly allocated to one of two arms, each using a different comparator health state. Respondents completed 10 or 11 TTO valuations and a series of follow-up questions examining their interpretations of the term "full health."

RESULTS: Interviews with 443 respondents were completed in 2014. The differences in mean values across arms are mostly small and nonsignificant. The two arms produced data of similar quality. There is evidence of interviewer effects. Health state 11111 was given a value of 1 by 98.2% of the respondents who valued it.

CONCLUSIONS: EQ-5D-5L values elicited by using the composite TTO approach are not greatly affected by the use of full health or 11111 as the comparator health state.