Evidence-based medicine, utilities, and quality of life.

Evidence-based medicine provides the highest quality of information for medical practitioners. At the top of the pyramid of evidence-based medicine are the prospective, randomized clinical trials and meta-analysis. Evidence-based medicine can be incorporated with quality-of-life parameters; the latter can be quantified using utility theory. With utility theory, utility values range from 0.0 (death state) to 1.0 (perfect health state). The higher the utility value, the better a person's quality of life. Interventional treatment can change the utility level experienced by a patient. A change in utility value induced by an interventional treatment can be amalgamated with the duration of the treatment effect to provide the number of quality-adjusted life-years (QALYs) gained by a specific treatment (QALYs = [gain in utility value] x [duration of treatment effect]). Thus, this formula takes into account both the improvement in quality of life and the improvement in length of life gained by a treatment. The number of QALYs gained by a treatment can then be incorporated with medical costs (discounted for the time value of money) to arrive at a final common denominator of $/QALY (cost per QALY). The parameter $/QALY can be used to compare the cost-effectiveness of interventional treatments across diverse specialties in medicine. In essence, this methodology allows a measure of the cost-effectiveness of a treatment that incorporates the highest quality of scientific information, clinical efficacy, patient quality-of-life preferences, and realistic costs.