Background. Many aspects of valuation study designs are poorly understood, and the size and composition of health states used in valuation studies vary widely. Our aims were to investigate the impact of the selection of a subset of EQ-5D health states in generating a set of visual analog scale (VAS)–based values. Our aims were to investigate the optimal number of health states, the sample size required per health state, and which combinations of health states are required to establish a EQ-5D VAS value set. Methods. Data were drawn from a United Kingdom (UK) general population postal survey in which all health states defined by EQ-5D were evaluated using VAS. We used a simulation approach to address each question, and the performance of each estimation model was assessed by the average value of the mean absolute errors. Results. Despite the constraint of the small sample size in the study dataset, the results suggest that the optimal number of states for a valuation study is 32, 100 observations per health state were sufficient, and multiple subsets of health states were feasible. Conclusions. Selecting health states not included in the “Measurement and Valuation of Health” dataset in valuation studies is quite specifically encouraged. However, it remains prudent to ensure that the selection of health states covers as wide a range of severity as possible. Setting the number of observations per health state to 150 might allow for correction of any errors in data collection or processing. The extent to which the results of this study based on VAS valuation data can be safely generalized to the design of time tradeoff valuation studies remains an open question.
KaplanRBushJBerryC. Health status: types of validity and the index of well-being. Health Serv Res. 1976;11:478–507.
2.
KaplanRAndersonJ. A general health policy model: update and application. Health Serv Res. 1988;23:203–35.
3.
BrazierJUsherwoodTHarperRThomasK. Deriving a preference-based single index from the UK SF-36 Health Survey. J Clin Epidemiol. 1998;51(11):1115–28.
4.
BrazierJRobertsJDeverillM. The estimation of a preference-based measure of health from the SF-36. J Health Econ. 2002;21(2):271–92.
5.
BrookR. EuroQol: the current state of play. Health Policy. 1996;37:53–72.
6.
RabinRde CharroF. EQ-5D: a measure of health status from the EuroQol Group. Ann Med. 2001;33:337–43.
7.
DolanP. Modeling valuations for EuroQol health states. Med Care. 1997;35(11):1095–108.
8.
BrazierJRatcliffeJSalomonJATsuchiyaA. Measuring and Valuing Health Benefits for Economics Evaluation. Oxford: Oxford University Press; 2007.
9.
BadiaXRosetMHerdmanMKindP. A comparison of UK and Spanish general population time trade off values for EQ-5D health states. Med Decis Making. 2001;21:7–16.
10.
Wittup-JensenULauridsenTGudexCBrooksRPedersonM. Estimating Danish EQ-5D tariffs using TTO and VAS. In: NorinderAPedersenKRoosP, eds. Proceedings of the 18th Plenary Meeting of the EuroQol Group. Lund, Sweden: The Swedish Institute for Health Economics; 2002; pp 257–266.
11.
TsuchiyaAIkedaSIkegamiN. Estimating an EQ-5D population value set: the case of Japan. Health Econ. 2002;11:341–53.
12.
ShawJWJohnsonJACoonsSJ. US valuation of the EQ-5D health states: development and testing of the D1 valuation model. Med Care. 2005;43(3):203–20.
13.
CleasCGreinerWUberASchulenburgJ-M. An interview-based comparison of the TTO and VAS values given to EuroQol states of health by the general German population. In: GreinerWSchulenburgJ-MPiercyJ, eds. Proceedings of the 15th Plenary Meeting of EuroQol Group. Uni-Verlag Witte, Germany: Centre for Health Economics and Health Systems Research, University of Hannover; 1998; pp 3–38.
14.
MacranSKindP. Valuing EQ-5D health states using a modified MVH protocol: preliminary results. In: BadiaXHerdmanMRosetM, eds. Proceedings of the 16th Plenary Meeting of the EuroQol Group. Sitges, Spain: Institut de Salut Publica de Catalunya; 1999; pp 205–239.
15.
LamersLMcDinnellJStalmeierPKrabbePBusschbachJ. The Dutch tariff: results and arguments for an effective design for national EQ-5D valuation studies. Health Econ. 2006;15:1121–32.
16.
KindPMacranSHennessyS. Measuring social preferences for EQ-5D health states: results from a saturation study. In: Prevolnik RupelV, ed. Proceedings of the 20th Plenary Meeting of the EuroQol Group. Bled, Slovenia: Institute of Public Health of the Republic of Slovenia; 2003; pp 153–162.
17.
ChuangLHKindP. The distribution of values for health. Presented at: 25th Plenary Meeting of the EuroQol Group; 11–13 September 2008; Baveno, Italy.
18.
The MVH Group. The Measurement and Valuation of Health: First Report on the Main Survey. York: Centre for Health Economics, University of York; 1994.
19.
BusschbachJMcDinnellJEssink-BotMvan HoutB. Estimating parametric relationships between health description and health valuation with an application to the EuroQol EQ-5D. J Health Econ. 1999;18:551–71.
20.
KrabbePStalmeierPLamersLBusschbachJ. Testing the interval-level measurement property of multi-item visual analogues scales. Qual Life Res. 2006;15:1651–61.
21.
WeijnenTNieuwenhuizenMOhinmaaAde CharroF. Construction of the EQ-net VAS and TTO databases. In: BrookRRabinRDe CharroF, eds. The Measurement and Valuation of Health Status Using EQ-5D: A European Perspective. Dordrecht, the Netherlands: Kluwer Academic Publishers; 2003; pp 55–80.
