Modelling the survival time among adult HIV/Aids patients under antiretroviral therapy In Moi Teaching and Referral Hospital, Kenya

Abstract

Survival modelling is technique which exploits repeated measures of continuous covariates to predict explanatory variables' effects on the response factor. The survival modelling helps design interventions in the health sector, which has seen one of its applications in the management of Human Immune Virus/ Acquired Immune Deficiency Syndrome (HIV/AIDS). However, despite improvement in Anti- Retroviral Therapy (ART) interventions over the years, the observed disease effects (morbidity, progression and mortality) remain high and vary across geographical borders. The general objective of the study was to model the survival time among adult HIV/AIDS patients’ under ART in Moi Teaching and Referral Hospital (MTRH) Kenya. Specifically, the study aimed at determining the mean and median survival times among this cohort of patients, fit Cox proportional hazard regression model to adult HIV/AIDS patients data and determine predictors of their survival. A retrospective study design was adopted where a target population of 10,038 patients who were on ART and were enrolled between January 2005 and January 2007 were investigated for a ten years follow-up period. Survival and hazard functions were used to determine the mean and median survival times. Kaplan Meier estimator was used to measure the overall survival trend and compare the survival time by gender. The Cox proportional hazard regression model (CPHRM) was fitted to the data using log partial likelihood function. The log rank test and 95% confidence Interval (C.I) were used to analyze the significance of the hazard ratios of each variable. The sample was constituted of 2,985(29.7%) male and 7,053(70.3%) females. From the data, censored patients consisted of 9,833(98%), while 205(2%) died. The results showed that the median and mean survival times after ART initiation were 10.00 and 9.06 years, respectively. HIV severity with Unadjusted Hazard Ratio (UHR) [UHR =0.729, p=0.032], level of education [lower UHR=0.952, p= 0.019], and ART perfect adherence [UHR=0.668, p=0.004] positively influenced patient survival time. Patient’s gender [male UHR= 1.633, p< 0.001] showed negative effect on patient survival time. None of the patient's covariates were jointly significant predictor of survival time in the multivariate Cox model. However, adjusting for other factors in the model, HIV severity with Adjusted Hazard Ratio (AHR) [AHR1.18, p=0.735], underweight measured by Body Mass Index (BMI) <18.5kg/m 2 in reference to 18.5- <25kg/m 2 [AHR=1.65, p=0.847] patients’ male gender [AHR=1.884, p=0.19] and ART perfect adherence at disease latter stage [AHR=1.393,p=0.498] increases the risk of mortality by 18%, 65%,88.4% and 39.3% respectively. In conclusion, ART perfect adherence enhance longer survival time in MTRH, The CPHRM fitted well to study data hence described the data optimally. HIV severity, gender, level of education and ART adherence were independent significant predictors of survival time whereas age and BMI were not. The study recommends the initiation of ART when CD4 count is at least 350mm 3 , male patients should do compulsory regular screening to avoid late diagnosis and delayed presentation for ART medication and MTRH should do sensitization on the importance of perfect adherence at early stages of the disease.