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.