Understanding quality-adjusted life years and their application to pharmacoeconomic research.
OBJECTIVE
To provide a basic overview of quality-adjusted life years (QALYs) and their application in cost-effectiveness analysis (CEA), compare and contrast QALYs with other health-related quality-of-life (HRQOL) assessments, describe current controversies regarding QALYs, and provide comparisons between QALY instruments.


METHODS
The literature regarding HRQOL and QALYs was reviewed and key issues are summarized.


RESULTS
QALYs provide relative preferences of patients for different health states. They range from 0, representing death, to 1.0, representing optimal health. QALYs are distinguished from other HRQOL assessments in that they provide a summary measurement that incorporates quantity of life in addition to HRQOL. When QALYs are used as the outcome measure in CEA, a cost per QALY is calculated. The Panel on Cost Effectiveness in Health and Medicine has recommended that QALYs be used as outcome measures in CEA; when QALYs are used in CEA, comparisons between treatments for different illnesses as well as within an illness are possible. The three most commonly used preference measurement techniques in determining QALYs are visual analog scales, time trade-off, and standard gamble. Controversies regarding QALYs include which preference measurement technique is most appropriate, whether QALY assessments should be obtained from patients or the community, and how to address states, such as coma, that individuals sometimes assess as worse than death. QALY instruments can be compared regarding preference measurement technique, HRQOL domains assessed, ease of administration, validity, reliability, and sensitivity.


CONCLUSIONS
When used appropriately, QALYs provide valuable outcome measures for pharmacoeconomic research.
Veterans Affairs Cooperative Studies Program, Clinical Research Pharmacy Coordinating Center, College of Pharmacy, University of New Mexico, Albuquerque 87106, USA. dennis.raisch@csp.research.med.va.gov
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D003362:Cost-Benefit Analysis; D017850:Economics, Pharmaceutical; D006801:Humans; D010818:Practice Patterns, Physicians'; D011788:Quality of Life; D019057:Quality-Adjusted Life Years; D012106:Research; D012680:Sensitivity and Specificity