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Title: Tuberculosis control in a South African community with high HIV prevalence : the role of intensified case-finding and antiretroviral therapy
Author: Kranzer, Katharina
ISNI:       0000 0004 2721 5503
Awarding Body: London School of Hygiene & Tropical Medicine
Current Institution: London School of Hygiene and Tropical Medicine (University of London)
Date of Award: 2012
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This thesis investigates active TB case finding and antiretroviral therapy for tuberculosis control in a setting with high HIV prevalence in Cape Town, South Africa. Many countries in sub-Saharan Africa have seen a worsening tuberculosis epidemic since the 1990s. Rising tuberculosis incidence rates have largely been attributed to high HIV prevalence in this region. Conventional tuberculosis control efforts focus on passive case finding and high cure rates in smear-positive patients, achieved through short course chemotherapy. These control strategies are insufficient in controlling the tuberculosis epidemic where HIV prevalence is high. Additional control strategies have been proposed, including active tuberculosis case finding, isoniazid preventive therapy for HIV infected individuals, infection control and antiretroviral therapy. The feasibility, uptake, yield, treatment outcomes and costs of population-based active tuberculosis case finding are investigated in the first part of the thesis. The second part determines losses along the HIV care pathway, community antiretroviral coverage and the association between coverage and tuberculosis risk. The main finding is that population-based active tuberculosis case finding linked to a mobile HIV testing service had a high uptake and yield. Treatment outcomes in patients diagnosed through active case finding were as good as outcomes in patients diagnosed through passive case finding in primary care clinics in Cape Town. Costs were USD 1,177 per TB case diagnosed and USD 2,458 per 3 successfully treated TB case, in an incremental costing analysis adopting a health service provider perspective. Analysis of the HIV care pathway in a peri-urban impoverished settlement in the greater area of Cape Town highlighted substantial losses along the pathway between HIV diagnosis and antiretroviral therapy. These results illustrate the operational challenges in achieving high treatment coverage. Antiretroviral coverage in this community increased from 18% in 2004 to 84% in 2009. Increasing antiretroviral coverage was associated with decreasing tuberculosis risk among patients receiving antiretroviral therapy, even controlled for timeupdated CD4 count, suggesting an effect on transmission, not just on individual risk reduction. The impact of active tuberculosis case finding and antiretroviral therapy on tuberculosis incidence on a population level was beyond the scope of this thesis. Large scale cluster randomized controlled trials are needed to investigate the effect of these strategies on tuberculosis control. In the meantime researchers conducting active tuberculosis case finding studies should be encouraged to collect data on treatment outcomes and costs. In addition further interventions are needed to increase retention and linkage to care in individuals prior to initiating antiretroviral therapy.
Supervisor: Lawn, Stephen ; Wood, Robin Sponsor: Wellcome Trust
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral