iBMG/iMTA, Erasmus University, PO Box 1738, 3000, DR, Rotterdam, The Netherlands.
Eur J Health Econ. 2012 Aug;13(4):491-500. doi: 10.1007/s10198-011-0318-y. Epub 2011 May 15.
The time tradeoff (TTO) method is often used to derive Quality-Adjusted Life Year health state valuations. An important problem with this method is that results have been found to be responsive to the procedure used to elicit preferences. In particular, fixing the duration in the health state to be valued and inferring the duration in full health that renders an individual indifferent, causes valuations to be higher than when the duration in full health is fixed and the duration in the health state to be valued is elicited. This paper presents a new test of procedural invariance for a broad range of time horizons, while using a choice-based design and adjusting for discounting. As one of the known problems with the conventional procedure is the violation of constant proportional tradeoffs (CPTO), we also investigate CPTO for the alternative TTO procedure. Our findings concerning procedural invariance are rather supportive for the TTO procedure. We find no violations of procedural invariance except for the shortest gauge duration. The results for CPTO are more troublesome: TTO scores depend on gauge duration, reinforcing the evidence reported when using the conventional procedure.
时间权衡（TTO）方法常用于推导出质量调整生命年健康状态的估值。这种方法的一个重要问题是，结果被发现对偏好 elicitation 所使用的程序敏感。具体来说，固定待评估健康状态的持续时间，推断使个体无差异的完全健康状态的持续时间，会导致估值高于当完全健康状态的持续时间固定且待评估健康状态的持续时间被 elicitation 时的情况。本文提出了一种新的测试，用于广泛的时间范围的程序不变性，同时使用基于选择的设计并调整折现率。由于传统程序的一个已知问题是违反恒定比例权衡（CPTO），我们还为替代 TTO 程序研究了 CPTO。我们关于程序不变性的发现对 TTO 程序相当支持。我们除了最短的测量时间外，没有发现违反程序不变性的情况。CPTO 的结果则更为麻烦：TTO 得分取决于测量时间，这强化了使用传统程序时报告的证据。
