title: Building uncertainty into cost-effectiveness rankings: portfolio risk-return tradeoffs and implications for decision rules.
abstract: BACKGROUND
  Current principles of cost-effectiveness analysis emphasize the rank ordering of programs by expected economic return (eg, quality-adjusted life-years gained per dollar expended). This criterion ignores the variance associated with the cost-effectiveness of a program, yet variance is a common measure of risk when financial investment options are appraised. Variation in health care program return is likely to be a criterion of program selection for health care managers with fixed budgets and outcome performance targets.
  
  
  METHODS
  Characterizing health care resource allocation as a risky investment problem, we show how concepts of portfolio analysis from financial economics can be adopted as a conceptual framework for presenting cost-effectiveness data from multiple programs as mean-variance data.
  
  
  RESULTS
  Two specific propositions emerge: (1) the current convention of ranking programs by expected return is a special case of the portfolio selection problem in which the decision maker is assumed to be indifferent to risk, and (2) for risk-averse decision makers, the degree of joint risk or covariation in cost-effectiveness between programs will create incentives to diversify an investment portfolio.
  
  
  CONCLUSIONS
  The conventional normative assumption of risk neutrality for social-level public investment decisions does not apply to a large number of health care resource allocation decisions in which health care managers seek to maximize returns subject to budget constraints and performance targets. Portfolio theory offers a useful framework for studying mean-variance tradeoffs in cost-effectiveness and offers some positive predictions (and explanations) of actual decision making in the health care sector.
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, and Centre for Evaluation of Medicines, St Joseph's Hospital, Hamilton, Ontario, Canada. obrienb@mcmaster.ca
authors.forename: B J
authors.initials: BJ
authors.lastname: O'Brien
authors.forename: M J
authors.initials: MJ
authors.lastname: Sculpher
mesh_terms: D003362:Cost-Benefit Analysis / Q000191:economics* / Q000379:methods / Q000706:statistics & numerical data; D003659:Decision Making, Organizational; D003661:Decision Support Techniques; D015276:Health Care Rationing / Q000191:economics / Q000706:statistics & numerical data; D006801:Humans; D007449:Investments / Q000191:economics* / Q000706:statistics & numerical data; D019057:Quality-Adjusted Life Years; D012051:Reimbursement Mechanisms / Q000191:economics / Q000706:statistics & numerical data; D020414:Risk Sharing, Financial / Q000191:economics* / Q000379:methods / Q000706:statistics & numerical data