Dictionary of Evidence-based Medicine.pdf

158 Dictionary of Evidence-based Medicine
diseases) in preference to, say, the rarer genetic diseases, a result referred
to as the perverse taste paradox. Cases of doctors withholding heart surgery
for smokers, on the basis that the resources would be better spent elsewhere,
have also attracted much controversy (Mills JS (1962) Utilitarianism.
Fontana, London. Entwistle V, Bradbury R, Pehl L et al. (1996) Media
coverage of child B case. BMJ. 312:1587-90).
Utility
The concept of utility has its roots in the philosophy of utilitarianism,
closely associated with the work of the 18th century philosopher Jeremy
Bentham. He described utility thus: 'By utility is meant that property in
any object whereby it tends to produce benefit, advantage, pleasure, good
or happiness or to prevent the happening of mischief, pain, evil or unhappiness
to the party whose interest is considered' (Bentham J (1990) Introduction
to the principles of morals and legislation. Athlone Press, London, first
published 1789).
Generally, utility can be defined as the benefits derived from consumption.
Utility as proposed by Pareto, for example, is considered to be something
personal and therefore non-comparable between persons (see under
Efficiency). However, over recent years, the view that the utilities of particular
health states are sufficiently consistent among individuals to provide
an average value and a basis for rating health states has been gaining
ground. In health economic analyses and EBM, utility is a measure of
preference for a particular level or state of health; in other words, the
benefits arising from being in the preferred state. Its measurement is
difficult but one approach is to ask the individual what proportion of his
normal life expectancy he would be willing to trade off to retain a particular
health state (e.g. ability to see). The utilities we assign to particular
health states are affected by our personal circumstances (e.g. age and
occupation). For example, executives are willing to assign a higher utility
to preserving normal speech than fire-fighters. Utilities are usually scaled
to values in the range 0-1.
Perhaps the most widely known utility scale is the Rosner and Watts
matrix in which a state of health characterized by an absence of disability
and freedom from stress is given the maximum weight of 1. Being chairbound
and in a state of severe stress is assigned a value of zero while being
bed-ridden and in severe distress is given a negative score of -1.5.
Alternative methods for eliciting utilities include: (i) use of an analogue
rating scale (0 = death, 1 = perfect health and values in between represent
varying degrees of ill health); (ii) time trade-off whereby patients are asked
to say how many years of their remaining lives they would be willing to