Estimation of mean quality adjusted survival time

In clinical studies, we often consider not only patients' survival time, bu t also their quality of life. Quality adjusted life years (QALY) is an inte grated measure of medical outcome that combines a patient's quantity and qu ality of life. Estimation of mean QALY for a group of patients is complicat ed by the fact that some patients are censored. The conventional approach i s to obtain the Kaplan-Meier estimate of the survival function associated w ith individual QALYs and then use the area under the Kaplan-Meier curve as an estimate of mean QALY. Glasziou, Simes and Gelber showed that this metho d is biased because censoring at the nominal time scale is informative for predicting unobserved QALYs. In this paper, we propose a methodology for co nsistent estimation of mean QALY. Simulation studies are conducted to inves tigate the relative performance of the new method and the conventional meth od. Copyright (C) 1999 John Wiley & Sons, Ltd.