1 A Joint Model Approach for Evaluating the Efficacy of HAART Treatment for AIDS patients in Taiwan

In recent years, benefits of Highly Active Antiretroviral Therapy (HAART) conferred on the morbidity and mortality of HIV/AIDS patients have been observed in numerous studies, mostly in industrialized countries where both AIDS incidence and the mortality resulting from AIDS have been declining. In this study, we make use of a cohort data of 138 AIDS patients in Taiwan, where the annual number of AIDS incidence is still increasing, to investigate the impact of HAART on survival time from onset of AIDS to death, by attempting to identify the association between patterns of CD4 counts and survival times for the HAART and non-HAART groups. Complications in data used, such as CD4 counts measured intermittently at different time points for different patients, measurement errors, or measurements unavailable after the survival time, could result in biased inferences for this study. Therefore we make use of a joint modeling approach including graphic techniques to model survival time and the time-dependent CD4 count simultaneously, by which we are able to derive unbiased and efficient estimators. The statistical inferences and graphi