Methods for evaluating health quality are central to medical cost-effectiveness analyses. The most important such method is the quality-adjusted life year (or QALY), in which a patient's length of life is given weight proportional to quality of health. However, numerous studies have demonstrated that the correlation between measured QALYs and a patient's current health is at best modest. Moreover, it is known that individuals may trade lifetime for improved health quality when remaining lifetime is long, but not when it is short; and that those with poor health quality may prefer to survive only until important life milestones are achieved and no longer. Current QALY models do not accomodate these sorts of phenomena.
To address these concerns, the investigators will examine methods for incorporating life goals into health preference models. The QALY model already addresses "ongoing goals" that have impact proportional to length of life, such as minimizing chronic pain or maintaining physical mobility. Other goals, termed "extrinsic goals," such as completing an important project or seeing a child graduate from college, are qualitatively different; their achievement has impact independent of length of life. These are not addressed by QALYs. The investigators have generalized the QALY model to incorporate both ongoing goals and extrinsic goals.
Guided by this model, the investigators will conduct empirical studies to characterize the kinds of extrinsic goals that are important for the general public and medical patients. They will conduct theoretical studies investigating potential preference models for extrinsic goals, methods for including multiple extrinsic goals, and impacts on published medical decision analyses when extrinsic goals are added. They will determine if extrinsic goals can help explain plausible behavior forbidden by the QALY model or yield better correlation of measured preferences with current health than does QALY.
Despite its limitations, the QALY model has become the standard for modeling patient preferences in medical cost-effectiveness analyses. The investigators' extrinsic-goal model constitutes a fundamental and original augmentation of this standard. It has the potential to benefit society by substantially broadening the types of patient and community preferences included in these analyses.
