The well-year of life as a basis for patient decision-making.

Medical decision-making requires the integration on costs, risks, and benefits of treatment. Clinical side effects and benefits are typically expressed in terms of symptoms and clinical states of diseases. Integrating probabilistic information about different categories is often difficult from both the patient's and the clinician's perspectives. We offer a General Health Policy Model that expresses the benefits and side effects of treatment within a common unit. The model takes into consideration mortality, function (morbidity), and preference for health states. In addition, the model uses probability information to describe the prognosis or likelihood of transition among states over the course of time. The output of the model is a well-year which is defined as the equivalent of a completely well-year of life. The well-year is a comprehensive expression of benefits minus side effects that may be useful for individual patient decision-making.