Ubel Peter A, Richardson Jeff, Baron Jonathan
Health Services Research & Development, Veterans Affairs Medical Center, University of Michigan Health Care System, 300 North Ingalls, Room 7C27, Ann Arbor, MI 48109-0429, USA.
Health Policy. 2002 Aug;61(2):189-99. doi: 10.1016/s0168-8510(01)00238-x.
The person trade-off (PTO) has been advocated by some as an alternative measure for the purposes of cost-effectiveness analyses. However, the measurement properties of PTO elicitations are still being defined.
We presented subjects with two PTO scenarios. In the pre-existing paraplegia scenario, they were asked how many paraplegics' lives would have to be saved to be just as important as saving 100 'normal' people's lives. In the paraplegia onset scenario, they were asked how many patients who would experience the onset of paraplegia need to be saved to equal the benefit of saving 100 'normal' lives. We varied the order of the two scenarios across subjects to test whether PTO elicitations are susceptible to order effects. In addition, we varied whether subjects were required to provide a numerical response to the first elicitation.
Subjects' PTO indifference points for the two scenarios varied dramatically depending on the order with which they received the scenarios, and according to whether the first elicitation required a numerical response. For those subjects providing numerical responses to both elicitations, median PTO responses varied by a factor of close to two in the pre-existing paraplegia scenario and by a factor of eight in the paraplegia onset scenario. However, the magnitude of the order effect was significantly reduced when subjects were not asked to provide a numerical response to the first PTO elicitation.
PTO elicitations are susceptible to order effects. These order effects are partly due to numerical anchoring. However, other cognitive factors contribute to the order effect. Further research should clarify whether these order effects can be reduced.
一些人主张将个人权衡法（PTO）作为成本效益分析的一种替代方法。然而，PTO诱导的测量属性仍在界定之中。
我们向受试者呈现了两种PTO情景。在已有截瘫情景中，询问他们需要挽救多少截瘫患者的生命才与挽救100名“正常”人的生命同样重要。在截瘫发病情景中，询问他们需要挽救多少将会经历截瘫发病的患者才能等同于挽救100名“正常”人的生命所带来的益处。我们对不同受试者改变了两种情景的顺序，以测试PTO诱导是否易受顺序效应的影响。此外，我们还改变了是否要求受试者对首次诱导提供数值回答。
受试者对两种情景的PTO无差异点根据他们接收情景的顺序以及首次诱导是否要求提供数值回答而有显著差异。对于那些对两次诱导都提供数值回答的受试者，在已有截瘫情景中，PTO回答的中位数相差近两倍，在截瘫发病情景中相差八倍。然而，当不要求受试者对首次PTO诱导提供数值回答时，顺序效应的幅度显著降低。
PTO诱导易受顺序效应的影响。这些顺序效应部分归因于数值锚定。然而，其他认知因素也对顺序效应有影响。进一步的研究应阐明这些顺序效应是否能够降低。
