Michael Carter
Published: 07 August 2015
Starting antiretroviral therapy (ART) significantly reduces the risk of tuberculosis (TB) for patients in South Africa, investigators report in the online edition of AIDS. Overall, ART initiation was associated with a 45% reduction in TB risk, which was lower than the effectiveness observed in other research. The authors believe this difference is because of their rigorous methodology, which unlike earlier studies, took into account patients’ pre-treatment CD4 counts.
“The study shows that ART initiation was associated with a substantially reduced risk of TB in HIV-infected patients with CD4+ cell counts of 350 cells/mm or less,” write the investigators. “The results differ from previous studies in high TB burden countries including South Africa, in which effectiveness estimates were greater and in which effectiveness was not modified by CD4+ count.”
TB is the commonest AIDS-defining illness in Africa. However, there is some evidence that ART rollout is reducing TB incidence among HIV-infected patients in this region. South Africa has the worst HIV epidemic in sub-Saharan Africa with an estimated 6.3 million infected patients. A national ART programme was introduced in 2004, and by 2010 approximately 2.4 million patients had started HIV therapy. Data from government health services suggest that increasing access to ART has been accompanied by a fall in TB incidence. Moreover, a meta-analysis of eleven studies in low- and middle-income countries estimated that ART reduced TB risk or incidence by 65%.
However, this study had an important limitation in that it did not take into account patients’ pre-treatment CD4 counts.
To get a better understanding of the true impact of ART initiation of TB risk, an international team of investigators designed an observational cohort study involving approximately 74,000 individuals who received HIV care in Free State, South Africa, between 2004 and 2010. TB risk and incidence was compared between patients who started ART and those who did not. Results were modified to take into account factors known to be associated with TB risk, especially CD4 count.
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