Joint Modeling of Incidence of Tuberculosis and Change in Viral Load Over Time Among Adult HIV/AIDS Patients on Anti-Retroviral Therapy at Zewditu Memorial Hospital in Addis Ababa, Ethiopia

BACKGROUND: Globally, approximately 37.9 million people were living with HIV and one-third of these people are co-infected with tuberculosis (TB). However, little is known about predictors of tuberculosis incidence and its association with viral load. Thus, this study was aimed at assessing the incidence of tuberculosis and its predictors and its association with the longitudinal change in viral load over time among adult HIV/AIDS patients at Zewditu memorial hospital, Addis Ababa Ethiopia. METHODS: A retrospective follow-up study was conducted among 471 HIV patients. The proportional hazard assumption was checked for the survival sub-model and the longitudinal sub-model. Νormality assumption was checked. Then the joint model with time-dependent lagged parameterizations was fitted. The goodness of fit was checked using the Cox-Snell residual test and Akaike Information Criteria (AIC) was used for model selection. Finally, the hazard ratio with a 95% confidence interval (CI) with a corresponding P-value <0.05 was used. RESULTS: A total of 471 patients were followed for a minimum of 12 and a maximum of 48 months with a median follow-up time of 44 months [IQR (33, 46)]. The incidence rate was 3.08/1000 person-years (PY) with a 95% CI of [0.0023788, 0.003998). Age above 65 years adjusted hazard ratio (AHR) = 2.07, 95% CI: 1.06, 4.06), underweight at baseline (AHR = 2.29, 95% CI: 1.20, 4.35), past opportunistic infection (AHR = 2.98, CI: 1.23, 7.17) and 6th month lagged value of the viral load were significant predictors for being co-infected with TB. CONCLUSION: The incidence of TB among HIV/AIDS patients in Zewditu memorial hospital was low. Older age, underweight at baseline, and past opportunistic infection were significant predictors of time to TB co-infection. Thus, addressing significant predictors and strengthening continuous follow-up are highly recommended in the study setting.