Joint Modelling of the Relationship between CD4 Cell Count and Survival Analysis of HIV Infected Patients Receiving Antiretroviral Therapy, Gweru, Zimbabwe

Abstract

Introduction: The main objective of this research is to apply joint modelling technique to assess the relationship between cd4 cell count and survival of ART patients in Gweru, Zimbabwe. The Cox proportional hazards model is mainly used in modelling survival data when the true values of the time-varying covariates are observed. However, most of these measurements are observed with error and to circumvent this problem, measurements are taken longitudinally to reduce the bias caused using such observed measurements in the Cox proportional hazards models. Methods: We conducted secondary data analysis on the Gweru district ART cohort data for the period 2006 to 2010. The association between CD4 cell count and survival time of the patient was determined using a joint longitudinal-survival model. The factors that affected cd4 cell changes were determined using mixed linear regression model and factors associated with survival of ART patients was determined using a Cox proportional hazard model. Shared parameters were used to determine the association between cd4 cell count and survival of the ART patient. Results: A statistically significant direct effect of gender on survival was observed -0.003 (95% CI: -001, -0.002). Also, a highly negative significant association was observed -9.48 (95% CI: -11.7, -7.23), indicating that female patients with high levels of lncd4 had reduced hazard of death compared to male patients. Place of residents of the ART patient had a significant direct effect on survival -0.66 (95% CI: -0.01, 0.003). There is also a highly negative significant association -10.0 (95% CI: -12.4, -7.67), indicating that patients in urban areas and with high lncd4 cell counts had a reduced hazard of death compared to patients in rural areas. Age had a direct effect on survival as the hazard of death increases as we move from one age group to another. A highly negative significant association was observed -9.4 (95% CI: -11.6, -7.17) indicating that the hazard of death for patients with high lncd4 decreases as we move down the age groups.