9.5.3 Quality or Disability Adjusted Life Year

Knows What is Meant by a Quality or Disability Adjusted Life Year and the Rationale for Using These Measures

Health economics is a branch of economics that focuses on the application of economic principles and methods to the health sector. It is concerned with the allocation of scarce resources in healthcare to achieve maximum health benefits. Quality-adjusted life year (QALY) and disability-adjusted life year (DALY) are measures of health outcomes commonly used in health economics. This teaching piece provides an overview of these measures and their rationale for use in healthcare decision-making.

Quality-Adjusted Life Year (QALY):

QALY is a measure of health outcome that combines the length of life with the quality of life. It is calculated by multiplying the number of years of life gained from a particular intervention by a utility score that reflects the quality of life experienced during those years. Utility scores range from 0 (representing death) to 1 (representing perfect health).

For example, if a patient undergoes a surgical intervention that increases their life expectancy by five years and they report a utility score of 0.8 for those five years, their QALY gain would be 4 (5 x 0.8).

Disability-Adjusted Life Year (DALY):

DALY is a measure of health outcome that takes into account both premature death and disability. It is calculated by summing the years of life lost due to premature death and the years lived with disability. The disability weight is a measure of the severity of the disability, ranging from 0 (representing perfect health) to 1 (representing death).

For example, if a patient suffers from a chronic disease that reduces their life expectancy by 10 years and also causes them to live with a disability that has a disability weight of 0.5 for 5 years, their DALY would be 12.5 (10 years of life lost plus 0.5 x 5 years lived with disability).

The rationale for using QALY and DALY:

QALY and DALY are commonly used in healthcare decision-making because they provide a way to compare the benefits of different interventions on a common scale. By converting health outcomes into a single measure, it is possible to compare the benefits of interventions across different diseases, populations, and settings.

QALY and DALY also provide a way to account for both the quantity and quality of life gained from an intervention. This is important because some interventions may increase life expectancy but have a negative impact on quality of life, while others may have a smaller impact on life expectancy but a greater impact on quality of life.

References:

1. Marseille, E., Larson, B., Kazi, D. S., Kahn, J. G., Rosen, S., & Franck, N. (2015). Thresholds for the cost–effectiveness of interventions: alternative approaches. Bulletin of the World Health Organization, 93(2), 118-124G.