title: A systematic review of studies eliciting willingness-to-pay per quality-adjusted life year: does it justify CE threshold?
abstract: BACKGROUND
  A number of studies have been conducted to estimate willingness to pay (WTP) per quality-adjusted life years (QALY) in patients or general population for various diseases. However, there has not been any systematic review summarizing the relationship between WTP per QALY and cost-effectiveness (CE) threshold based on World Health Organization (WHO) recommendation.
  
  
  OBJECTIVE
  To systematically review willingness-to-pay per quality-adjusted-life-year (WTP per QALY) literature, to compare WTP per QALY with Cost-effectiveness (CE) threshold recommended by WHO, and to determine potential influencing factors.
  
  
  METHODS
  We searched MEDLINE, EMBASE, Psyinfo, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Center of Research Dissemination (CRD), and EconLit from inception through 15 July 2014. To be included, studies have to estimate WTP per QALY in health-related issues using stated preference method. Two investigators independently reviewed each abstract, completed full-text reviews, and extracted information for included studies. We compared WTP per QALY to GDP per capita, analyzed, and summarized potential influencing factors.
  
  
  RESULTS
  Out of 3,914 articles founded, 14 studies were included. Most studies (92.85%) used contingent valuation method, while only one study used discrete choice experiments. Sample size varied from 104 to 21,896 persons. The ratio between WTP per QALY and GDP per capita varied widely from 0.05 to 5.40, depending on scenario outcomes (e.g., whether it extended/saved life or improved quality of life), severity of hypothetical scenarios, duration of scenario, and source of funding. The average ratio of WTP per QALY and GDP per capita for extending life or saving life (2.03) was significantly higher than the average for improving quality of life (0.59) with the mean difference of 1.43 (95% CI, 1.81 to 1.06).
  
  
  CONCLUSIONS
  This systematic review provides an overview summary of all studies estimating WTP per QALY studies. The variation of ratio of WTP per QALY and GDP per capita depended on several factors may prompt discussions on the CE threshold policy. Our research work provides a foundation for defining future direction of decision criteria for an evidence-informed decision making system.
authors: Faculty of Pharmaceutical Sciences, Prince Songkla University, Hatyai, Thailand.
authors: Khachapon
authors: K
authors: Nimdet
authors: School of Pharmacy, Monash University Malaysia, Selangor, Malaysia; Center of Pharmaceutical Outcomes Research (CPOR), Department of Pharmacy Practice, Faculty of Pharmaceutical Sciences, Naresuan University, Phitsanulok, Thailand; School of Pharmacy, University of Wisconsin, Madison, United States of America; School of Population Health, University of Queensland, Brisbane, Australia.
authors: Nathorn
authors: N
authors: Chaiyakunapruk
authors: Faculty of Pharmaceutical Sciences, Prince Songkla University, Hatyai, Thailand.
authors: Kittaya
authors: K
authors: Vichansavakul
authors: Faculty of Pharmaceutical Sciences, Prince Songkla University, Hatyai, Thailand.
authors: Surachat
authors: S
authors: Ngorsuraches
mesh_terms: D000328:Adult; D000368:Aged; D003362:Cost-Benefit Analysis; D003657:Decision Making; D005260:Female; D005102:Health Expenditures; D006801:Humans; D008297:Male; D008875:Middle Aged; D018803:Models, Economic; D011788:Quality of Life / Q000523:psychology*; D019057:Quality-Adjusted Life Years