What is a QALY?

In the previous step, we saw that the use of different PROMs for different interventions and for different patient groups means that we do not have a single measure of benefit, which makes comparing healthcare interventions nearly impossible.

In this video, Katherine demonstrates how to calculate Quality Adjusted Life Years or QALYs; a unit of benefit that can be used to assess the extent of the benefits gained from a variety of healthcare interventions.

To calculate QALYs, we multiply the length of life expected to be gained by the new treatment or invention by the quality of life a patient can expect to have.

• The length of life can be measured in trials, but will often require extrapolation beyond this period using assumptions and other data sources. For example, if we know that a drug reduces cholesterol and we know that cholesterol is linked to heart disease and therefore to mortality, we can use this information to estimate length of life. Alternatively, we can use large epidemiology studies that help estimate life expectancy based on conditions, age and gender.

• Quality of life is measured on a 0 – 1 scale and this score represents the value of different levels of health. We’ll be exploring what these numbers mean and where they come from later on in the week.