Assessment of quality of life.

Assessment of quality of life has emerged in recent years as an important part of the overall evaluation of drug therapy and health care in general. Measurement techniques for this difficult assessment range from simple unqualified questions on patient well-being to complex statistical analyses of a wide range of lifestyle and activity variables. The factors that influence quality of life during chronic drug therapy differ in the treatment of symptomatic (e.g., heart failure) vs asymptomatic (e.g., hypertension) disease, and include drug side effects, relief of symptoms, improved prognosis, return to work, physical activity and the need for further hospital treatments. The manifestation of quality of life varies for different people leading to lack of agreement on the precise definition. The absence of standardization of methods of measurement also contributes to this and leads to lack of comparability of studies and unreasonable claims by some drug manufacturers. Further complicating issues in multicenter trials across countries include language problems and interethnic differences in "sickness" behavior. The recently introduced quality-adjusted life year (QALY) index, designed to take account of both the quality and duration of life in assessing the outcome of treatments, may avoid some of these problems. By classifying illness states (the Rosser index) on the basis of disability and distress, and comparing outcomes in terms of improved prognosis, QALYs have already been used for cost/benefit analyses of a number of new and expensive therapies. Like other methods, QALYs have problems related to variability in individual appreciation of life values. To date, a perfect method of quality of life assessment remains elusive.