Last update:
07-Jul-2004

In this article, the utility theory and its refinements (prospect theory, cumulative prospect theory) and the regret theory is reviewed. The incorporation of qualified and measured patient preferences (utilities) regarding the outcomes of clinical decisions has become mandatory for objective and ethical reasons as it is the patient on whom the outcome of a decision will have the main impact. Patients’ preferences for the alternative outcomes arising from different courses of action can be measured and expressed as utilities which reflect the reality of a specific situation. The definition of utility is having identified the best and worst outcomes of a decision made under uncertainty, if the outcome X is valued equivalently to a gamble giving a chance of p at the best and a chance 1–p at the worst, then p is the utility of outcome plus on a utility scale of 0 to 1. Utility theory is based on axioms to which any rational person would adhere when considering the preferences. Transitivity dictates that if A is preferred to B and Β is preferred to C then, by logical necessity, A is preferred to C. Independence dictates that if Α is preferred to B, then a lottery offering A with probability p and C with a probability 1–p is preferred to a lottery offering B with probability p and C with probability 1–p, for any C. Methods for measuring utility are: (a) The standard gamble, where the utility is determined by finding the point where the attinde of the patient is indifference between living with the current health state and taking a gamble with a best and a worst outcome. (b) Time trade-off, where the utility for current health is determined by assessing the proportion of remaining life expectancy a person will trade in exchange for living in perfect health. (c) Visual analog scale where on a scale from 0 (death) to 100 (perfect health) the patient puts a mark on that point he/ she feels represents his/her current health situation. According to their attitudes toward the risk involved, patients are grouped as risk averse, risk prone and risk indifferent. Regret theory dictates that in the case of a failure to take the best available action there is a loss of opportunity which has been called regret, because retrospectively the decision already made causes the decision maker regret for not having taken the optimal action. Therefore, physicians making decisions under uncertainty usually prefer to prescribe rather than not to prescribe a drug, to order rather than not to order a test, in order to avoid or reduce regret from not treating, in the case where the disease is present, or not ordering a test in the case where the test would be positive (defensive medicine).

Key words: Expected utility, Medical decision making, Prospect theory, Rating scales, Regret, Utility.