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The potential effects of changing HIV treatment policy on tuberculosis outcomes in South Africa: results from three tuberculosis-HIV transmission models

Pretorius, Carela,*; Menzies, Nicolas A.b,*; Chindelevitch, Leonidc; Cohen, Tedd,e; Cori, Annef; Eaton, Jeffrey W.g; Fraser, Christophef; Gopalappa, Chaitraa; Hallett, Timothy B.g; Salomon, Joshua A.b,c; Stover, Johna; White, Richard G.h; Dodd, Peter J.h

doi: 10.1097/QAD.0000000000000085
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Objective(s): Many countries are considering expanding HIV treatment following recent findings emphasizing the effects of antiretroviral therapy (ART) on reducing HIV transmission in addition to already established survival benefits. Given the close interaction of tuberculosis (TB) and HIV epidemics, ART expansion could have important ramifications for TB burden. Previous studies suggest a wide range of possible TB impacts following ART expansion. We used three independently developed TB-HIV models to estimate the TB-related impact of expanding ART in South Africa.

Design: We considered two dimensions of ART expansion – improving coverage of pre-ART and ART services, and expanding CD4-based ART eligibility criteria (from CD4 <350 to CD4 <500 or all HIV-positive).

Methods: Three independent mathematical models were calibrated to the same data pertaining to the South African HIV–TB epidemic, and used to assess standardized ART policy changes. Key TB impact indictors were projected from 2014 to 2033.

Results: Compared with current eligibility and coverage, cumulative TB incidence was projected to decline by 6–30% over the period 2014-2033 if ART eligibility were expanded to all HIV positive individuals, and by 28–37% if effective ART coverage were additionally increased to 80%. Overall, expanding ART was estimated to avert one TB case for each 10–13 additional person-years of ART. All models showed that TB incidence and mortality reductions would grow over time, but would stabilize towards the end of the projection period.

Conclusion: ART expansion could substantially reduce TB incidence and mortality in South Africa and could provide a platform for collaborative HIV-TB programs to effectively halt HIV-associated TB.

aFutures Institute, Glastonbury, Connecticut

bCenter for Health Decision Science, Harvard School of Public Health

cDepartment of Global Health and Population, Harvard School of Public Health

dDivision of Global Health Equity, Brigham and Women's Hospital

eDepartment of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA

fMRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology

gDepartment of Infectious Disease Epidemiology, Imperial College London

hDepartment of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.

*Carel Pretorius and Nicolas A. Menzies contributed equally to the writing of this article.

Correspondence to Carel Pretorius, Futures Institute, Glastonbury, CT, USA. E-mail:

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© 2014 Lippincott Williams & Wilkins, Inc.