Quality Adjusted Life Years (QALY) measures the value and benefit of health outcomes. It’s used to guide and inform health policy and is accepted as an outcome measure in health economics, to quantify the effectiveness of a new treatment (e.g. new medication) compared to the current treatment for a particular condition or to compare the health benefit of a new treatment for one condition with the health benefit of a new treatment for a different condition, according to Physiopedia.
Deeper dive
QALYs can also be used to evaluate the cost effectiveness of a treatment; that is, how much the drug or treatment costs per QALY. This is the cost of prescribing a drug to provide one year of the best quality of life available and it is expressed in the U.S. as “$ per QALY.”
QALY combines mortality, measured as length of life, with morbidity, quality of life, into one number to determine how many additional months or years of a reasonable quality of life a person might gain.The formula used to calculate QALY assumes what’s known as a utility value (quality of life) between 1 = perfect health and 0 = dead.
- If someone has perfect health for a period of 1 year, they will be said to have one QALY. i.e. 1 Year of Life x 1 Utility Value = 1 QALY
- If someone lives in perfect health but only for half a year, that person will have 0.5 QALY. i.e. 0.5 Years of Life x 1 Utility Value = 0.5 QALY
- If someone lives for one year in a situation with 0.5 utility (half of perfect health) that individual will have 0.5 QALY i.e. 1 Year of Life x 0.5 Utility Value = 0.5 QALY
One limitation of QALY is that younger, healthier groups of people will have many times more QALYs than groups of older, more infirm individuals; therefore, QALY calculations may undervalue treatments which benefit the elderly or other groups with a lower life expectancy.