How Far Does Highly Active Antiretroviral Treatment Reduce TB Incidence among Children? A Marginal Structural Modeling Analysis, Southwest Ethiopia

BACKGROUND: Children younger than 15 years, carry almost 80% of the global burden of HIV/AIDS. HIV worsens the progression of latent TB to active TB disease. Although antiretroviral treatment has shown marked reduction in Tuberculosis incidence, TB continues to occur in Sub-Saharan countries including Ethiopia. The aim of this study was to investigate the impact of HAART on the incidence of tuberculosis among children infected with HIV in Southwest Ethiopia. METHODS: A retrospective cohort study was conducted between 2009 to 2014. We used chi-square test, and Mann-Whitney U test to compare non-HAART and HAART cohort. We estimated the effect of HAART on TB incidence using marginal structural model after adjusting for time-dependent confounders affected by exposure. RESULT: A total of 844 children were followed. We observed them for a median of 51 months (IQR 31) and a total of 2942.99 child-years. The overall TB incidence rate was 7.917 per 100 child years (95% CI, 6.933-9.002). TB incidence for specific HAART and non-HAART cohort were 7.67 per 100 child-years (95% CI, 6.318-9.217) and 8.17 per 100 child-years (95% CI, 6.772-9.767) respectively. From marginal structural modeling, children on HAART were 36% (HR=0.642, 95% CI 0.442-0.931, p<0.02) less likely to develop TB compared to those who were not. CONCLUSION: HAART reduced the hazard of TB in HIV-infected children by 36%. This is by far less than what is expected.