Willingness to pay per quality-adjusted life year: is one threshold enough for decision-making?: results from a study in patients with chronic prostatitis.

OBJECTIVE To estimate the willingness to pay (WTP) per quality-adjusted life year (QALY) ratio with the stated preference data and compare the results obtained between chronic prostatitis (CP) patients and general population (GP). METHODS WTP per QALY was calculated with the subjects' own health-related utility and the WTP value. Two widely used preference-based health-related quality of life instruments, EuroQol (EQ-5D) and Short Form 6D (SF-6D), were used to elicit utility for participants' own health. The monthly WTP values for moving from participants' current health to a perfect health were elicited using closed-ended iterative bidding contingent valuation method. RESULTS A total of 268 CP patients and 364 participants from GP completed the questionnaire. We obtained 4 WTP/QALY ratios ranging from $4700 to $7400, which is close to the lower bound of local gross domestic product per capita, a threshold proposed by World Health Organization. Nevertheless, these values were lower than other proposed thresholds and published empirical researches on diseases with mortality risk. Furthermore, the WTP/QALY ratios from the GP were significantly lower than those from the CP patients, and different determinants were associated with the within group variation identified by multiple linear regression. CONCLUSIONS Preference elicitation methods are acceptable and feasible in the socio-cultural context of an Asian environment and the calculation of WTP/QALY ratio produced meaningful answers. The necessity of considering the QALY type or disease-specific QALY in estimating WTP/QALY ratio was highlighted and 1 to 3 times of gross domestic product/capita recommended by World Health Organization could potentially serve as a benchmark for threshold in this Asian context.