Effect of Isoniazid Preventive Therapy on TB Incidence and Mortality among HIV patients on Highly Active Antiretroviral Treatment in Addis Ababa Public Health Facilities

Abstract

Abstract Introduction: HIV is the strongest risk factor for developing tuberculosis (TB) in those with latent or new Mycobacterium tuberculosis infection. In Ethiopia, timely initiation of Antiretroviral therapy (ART) and Isoniazid preventive therapy (INH) provision for HIV infected patients is recommended by the national TB/HIV collaborative activities guideline and its implementation has been started since 2007. However, there is no up to date information to quantify the number of incident TB cases and mortalities averted with proper implementation of this preventive strategy in Addis Ababa public health facilities. Objective: To determine the effect of Isoniazid preventive therapy on incidence of tuberculosis and all cause mortality among HIV infected patients who are on highly active anti-retroviral therapy (HAART) in Addis Ababa public health facilities from May-August 2019 Methods: Retrospective cohort study was conducted in selected public health facilities of Addis Ababa city administration among HIV patients on HAART enrolled in to the care from July 2012 to July 2017. The sources of data were the routine paper based national ART register, patient medical records and the computer data base. Data was entered on excel 2010, cleaned and exported to SPSS version 24 for analysis. Means, medians, frequencies, and interquartile ranges were employed as descriptive statistical analysis. Incidence rates in person-time are computed for ‘incident TB’ and all-cause mortality, and IRR is calculated to compare between groups. Multivariable cox-proportional hazards regression is employed to identify factors associated with incident TB cases and all-cause mortality. Results: A total of 930 patients were included in the study of which 57% of the patients were females with a mean age of 42.87 (SD=10.2) years. Overall TB incidence rate was 15.3/1000 (95% CI=11.6-19.8) person-months and INH exposure was found to have marked protection against TB (aHR=0.18; 95% CI=0.09-0.34) and mortality (aHR=0.08; 95% CI=0.02-0.25) in INH exposed patients. INH exposure (aHR=0.21, 95% CI=0.10-0.43), working functional status (aHR=0.24, 95% CI=0.08-0.71) WHO clinical stage 1 (aHR=0.12; 95% CI=0.04-0.41) were factors associated with incident TB cases whereas, INH exposure (aHR=0.07; 95% CI=0.02-0.29), WHO clinical stage 1 (aHR=0.10; 95% CI=0.03-0.39), clinical stage 2 (aHR=0.36; 95% CI=0.13-0.99) and, weight below 50kg (aHR=9.67; 95% CI=1.22-76.80) and 50-59kg (aHR= 9.1; 95% CI=1.15-72.6) were the factors significantly associated with mortality. Conclusion: INH is found very helpful in averting increased TB incidence and mortality among patients on HAART; therefore it is highly recommended to intensify its coverage and timely initiation among HIV patients. Earlier identification of HIV infected patients by maximizing the community awareness and targeted testing programs in public health facilities will be very helpful to provide the INH prophylaxis timely and curb the progress of the disease and development of TB.