QALY
A measure of the state of health of a person or group in which the benefits, in terms of
length of life, are adjusted to reflect the quality of life. One QALY is equal to 1 year of
life in perfect health.
QALYs are calculated by estimating the years of life remaining for a patient following a
particular treatment or intervention and weighting each year with a quality of life score
(on a zero to 1 scale). It is often measured in terms of the person's ability to perform
the activities of daily life, freedom from pain and mental disturbance. (1)
The quality-adjusted life year or quality-adjusted life-year (QALY) is a measure
of disease burden, including both the quality and the quantity of life lived. It is used in
assessing the value for money of a medical intervention. According to Pliskin et al.,
The QALY model requires utility independent, risk neutral, and constant proportional
tradeoff behaviour. The QALY is based on the number of years of life that would be
added by the intervention. Each year in perfect health is assigned the value of 1.0
down to a value of 0.0 for being dead. If the extra years would not be lived in full
health, for example if the patient would lose a limb, or be blind or have to use
a wheelchair, then the extra life-years are given a value between 0 and 1 to account for
this. (2)
(1) National Institute for Health and Care Excellence, UK, Glossary
(2) Wikipedia: Quality-adjusted life year (Visited on 05 January 2015)