In economic evaluations, how is a QALY best described?

• A. A fixed number of life years
• B. A patient satisfaction index
• C. A measure of total healthcare spending
• D. A preference-based measure of health utility

Answer: (D)

The main idea being tested is that QALYs are a preference-based measure of health utility used to quantify outcomes in economic evaluations. A QALY blends how long someone lives with how desirable or undesirable their health state is, according to preferences. The health state is given a utility value between 0 and 1 (0 = dead, 1 = perfect health), typically derived from population or patient preferences using methods like time trade-off or standard gamble, and often estimated from instruments such as EQ-5D or HUI.

You multiply the number of years lived in that health state by its utility to get QALYs. This lets you compare different health interventions on a common scale that accounts for both quantity and quality of life. For example, 2 years lived in a health state with a utility of 0.7 equals 1.4 QALYs. In contrast, 2 years in perfect health would be 2 QALYs, and 2 years in a poorer state with a utility of 0.4 would be 0.8 QALYs. This distinguishes QALYs from simply counting life years or from measures of satisfaction or spending, since it reflects valued health outcomes rather than just duration or costs.