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Quality of Life Research

, Volume 25, Issue 9, pp 2179–2191

First Online: 26 March 2016Accepted: 04 March 2016DOI: 10.1007-s11136-016-1266-x

Cite this article as: Augestad, L.A., Stavem, K., Kristiansen, I.S. et al. Qual Life Res 2016 25: 2179. doi:10.1007-s11136-016-1266-x


PurposeThe de facto standard method for valuing EQ-5D health states is the time trade-off TTO, an iterative choice procedure. The TTO requires a starting point SP, an initial offer of time in full health which is compared to a fixed offer of time in impaired health. From the SP, the time in full health is manipulated until preferential indifference. The SP is arbitrary, but may influence respondents, an effect known as anchoring bias. The aim of the study was to explore the potential anchoring effect and its magnitude in TTO experiments.

MethodsA total of 1249 respondents valued 8 EQ-5D health states in a Web study. We used the lead time TTO LT-TTO which allows eliciting negative and positive values with a uniform method. Respondents were randomized to 11 different SPs. Anchoring bias was assessed using OLS regression with SP as the independent variable. In a secondary experiment, we compared two different SPs in the UK EQ-5D valuation study TTO protocol.

ResultsA 1-year increase in the SP, corresponding to an increase in TTO value of 0.1, resulted in 0.02 higher recorded LT-TTO value. SP had little impact on the relative distance and ordering of the eight health states. Results were similar to the secondary experiment.

ConclusionThe anchoring effect may bias TTO values. In this Web-based valuation study, the observed anchoring effect was substantial. Further studies are needed to determine whether the effect is present in face-to-face experiments.

KeywordsTime trade-off Health state valuation Starting point Anchoring bias EQ-5D  Download fulltext PDF

Autor: Liv Ariane Augestad - Knut Stavem - Ivar Sønbø Kristiansen - Carl Haakon Samuelsen - Kim Rand-Hendriksen


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