Objectives. For contingent valuation to provide valid values for policy making, it is important that respondents be well informed about the goods they are asked to value. Few studies, however, have tested the impact of providing this information This study assessed the impact of risk information on patients' willingness to pay for autologous blood donation and derived the willingness to pay in a sample of informed patients.
Methods. Patients were randomized either to receive information about the risks of complications from allogeneic (volunteer) blood transfusions or to base their willingness to pay responses on their own prior knowledge. Four hundred twelve autologous blood donors were recruited from three study sites. Self-administered questionnaires collected information on willingness to pay, risk perceptions, and socioeconomic information.
Results. As predicted by our theoretical model, providing risk information reduced the variance in the willingness to pay for autologous blood donation. A tendency for information to reduce the willingness to pay was also found, suggesting that uninformed patients, on average, overestimate the risks of allogeneic blood transfusions. The median willingness to pay in the informed sample was approximately $750 to $1,100, depending on the estimation method, compared with $800 to $1,900 in the uninformed group. Willingness to pay was significantly related to perceived transfusion risk, personal income, and dread of transfusions.
Conclusions. Our results are consistent with an economic model where individuals update their prior risk perceptions with new information. The willingness to pay in the informed sample was far higher than the costs of autologous blood donation, suggesting that total benefits outweigh the costs of the procedure.