Willingness to pay: a valid and reliable measure of health state preference?
The development of methods to measure willingness to pay (WTP) has renewed interest in cost-benefit analysis (CBA) for the economic evaluation of health care programs. The authors studied the construct validity and test-retest reliability of WTP as a measure of health state preferences in a survey of 102 persons (mean age 62 years; 54% male) who had chronic lung disease (forced expiratory volume < 70%). Interview measurements included self-reported symptoms, the oxygen-cost diagram for dyspnea, Short-Form 36 for general health status, rating scale and standard gamble for value and utility of current health state relative to death and healthy lung functioning, and WTP for a hypothetical intervention offering a 99% chance of healthy lung functioning and a 1% chance of death. WTP was elicited by a simple bidding game. To test for starting-point bias, the respondents were randomly assigned to one of five starting bids. All health status and preference measurements except WTP (controlling for income) showed significant (p < 0.05) difference between disease-severity groups (mild/moderate/severe). WTP was significantly (p = 0.01) associated with household income, but other health status and preference measure were not. The measure most highly correlated with WTP was standard gamble (r = -0.46). There was no association between starting bid and mean WTP adjusted for income and health status. The test-retest reliability of WTP was acceptable (r = 0.66) but lower than that for the standard gamble (r = 0.82).(ABSTRACT TRUNCATED AT 250 WORDS)
O'Brien
B
B
Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
Viramontes
J L
JL
D000368:Aged; D000704:Analysis of Variance; D001294:Attitude to Health; D003362:Cost-Benefit Analysis / Q000379:methods*; D005260:Female; D005382:Financing, Personal / Q000706:statistics & numerical data; D006304:Health Status; D006801:Humans; D007182:Income; D008173:Lung Diseases, Obstructive / Q000175:diagnosis / Q000191:economics / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009864:Ontario; D011788:Quality of Life; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D026712:Value of Life