The 'utility' of the visual analog scale in medical decision making and technology assessment. Is it an alternative to the time trade-off?

Methods often used for the valuation of health states are the time trade-off (TTO) and the visual analog scale (VAS). The VAS is easier than the TTO and can be self-administered; however it usually leads to lower scores. In the literature a power transformation of group mean VAS scores to TTO scores has been proposed. We were able to replicate this finding of a power function. We found coefficients that were very similar to those from the literature, for 183 cancer patients. The relationship existed independently of disease state and health status.