Outcomes from treatments and other health-influencing activities have two basic components - the quantity and quality of life. Life expectancy is a traditional measure with few problems of comparison - people are either alive or not.
Attempts to measure and value quality of life is a more recent innovation, with a number of approaches being used. Particular effort has gone into researching ways in which an overall health index might be constructed to locate a specific health state on a continuum between, for example, 0 (= death) and 1 (= perfect health). Obviously the portrayal of health like this is far from ideal, since, for example, the definition of perfect health is highly subjective and it has been argued that some health states are worse than death.Uses
Construction of such measures has a number of uses - to identify public health trends for strategies to be developed, to assess the effectiveness and efficiency of health care interventions, or to determine the state of health in communities.
The Quality Adjusted Life Year (QALY) has been created to combine the quantity and quality of life. The basic idea of a QALY is straightforward. It takes one year of perfect health-life expectancy to be worth 1, but regards one year of less than perfect life expectancy as less than 1. Thus an intervention which results in a patient living for an additional four years rather than dying within one year, but where quality of life fell from 1 to 0.6 on the continuum will generate:-
- 4 years extra life @ 0.6 quality of life values 2.4
- less 1 year @ reduced quality (1 - 0.6) 0.4
- QALYs generated by the intervention 2.0
QALYs can therefore provide an indication of the benefits gained from a variety of medical procedures in terms of quality and life and survival for the patient. Another example is shown in the figure, where treatment provides a higher area under the QALY/time curve than does no treatment.
Value of QALYs
It is no use pretending that QALYs are anything but a crude measurement. It is necessary to be aware of their limitations - with the possibility of more research making the process more sophisticated and useful.
The use of QALYs in resource allocation decisions does mean that choices between patient groups competing for medical care are made explicit. QALYs have been criticised because there is an implication that some patients will be refused or not offered treatment for the sake of other patients and, yet such choices have been made and are being made all the time. However big the pot, choices still have to be made.