The reliability of willingness to pay for changes in health status.

One of the most common means to test for the temporal reliability of willingness-to-pay (WTP) values is the 'test-retest' method. However, few such tests have been conducted in healthcare, and the few that are focus on specific patient or professional groups, limiting their generalisability. In this article, a test-retest analysis of WTP for changes in health status from a general population sample found good reliability overall, with the level of reliability increasing with the overall amount of WTP and/or level of WTP as a proportion of income. The possible implications for the design and use of WTP studies in healthcare are outlined.