The use of conjoint analysis to elicit willingness-to-pay values. Proceed with caution?

There is a growing interest in the potential use of conjoint analysis (CA) as a tool for estimating patient preferences within the economic evaluation of healthcare technologies. It has been suggested that where cost is included as one of the attributes within the exercise, CA can be used to estimate willingness to pay (WTP) for healthcare interventions indirectly within the framework of cost-benefit analysis. While recognizing the potential advantages of CA as a technique for the assessment of benefits in health care, this paper recommends several avenues of investigation that need to be carefully explored before an informed judgment can be made as to the validity of eliciting WTP values using the CA methodology. It is argued that much can be learned from the use of qualitative research techniques in examining individuals' understanding and interpretation of CA questions where cost is included as an attribute in the exercise. Additionally, further research is required in defining techniques for establishing the most appropriate levels for the cost attribute in a CA exercise and in determining the sensitivity of WTP estimates to the levels that are chosen for the cost attribute.