What is a QALY best described as?

• A. A measure combining length and quality of life into a single index
• B. A purely economic cost measure
• C. A population risk estimate
• D. A clinical laboratory biomarker

Answer: (A)

Quality-adjusted life year is a measure that combines how long a person lives with how good that life is. Each year of life is weighted by a health-related quality-of-life value (from 0 for death to 1 for perfect health), and these weights are multiplied by the years lived to produce QALYs. This lets us compare medical interventions on overall benefit: not just longer survival, but better quality of life during that survival. For example, an intervention adding 2 years at a quality of life of 0.8 equals 1.6 QALYs, while one adding 3 years at a quality of life of 0.6 equals 1.8 QALYs, helping us see which option provides more total health benefit. It is not a pure economic cost measure, nor a population risk estimate, nor a clinical laboratory biomarker.