ArticlesEffect of household and community interventions on the burden of tuberculosis in southern Africa: the ZAMSTAR community-randomised trial
Introduction
The past two decades have seen an unprecedented rise in the burden of tuberculosis in southern Africa. Mathematical modelling1 and molecular epidemiology2, 3, 4 suggest that continuing transmission of tuberculosis, in the context of HIV infection, is the driving force. Community-based prevalence surveys have shown that much undiagnosed tuberculosis exists in communities,5, 6, 7, 8 with consequent transmission to the susceptible HIV-infected population.9 An estimated 80% of the world's cases of HIV-tuberculosis co-infection are in southern Africa; the estimated incidence of tuberculosis in South Africa is more than 900 per 100 000 people per year.10
Although there have been substantial advances in recommended strategies for management of tuberculosis in people with HIV infection,11 approaches that are currently recommended remain focused on services provided for individuals presenting with cough to local health services or those known to have HIV infection. The rationale for this clinic-based approach was reinforced by various studies of community-based case-finding from the era before HIV emerged as the predominant driver of coepidemics in southern Africa.12
In recognition of the fact that focusing solely on individuals who present to health facilities has not reduced tuberculosis, and the many barriers to access to health services, the Stop TB Partnership has included increased community involvement in the diagnosis and management of tuberculosis as part of the global plan to stop tuberculosis.13 Several interventions have been proposed or tested mostly involving case finding14, 15, 16 or case management.17, 18, 19 However, none of these studies has provided robust evidence for policy change. Assessment of the effect of interventions for tuberculosis at a public health level is challenging. Randomised study designs of interventions delivered within existing health services need to allocate whole communities to the same intervention group, and the outcomes must be measured in sufficiently large units to capture herd effects attributable to continuing transmission within the population. Studies of approaches to reduce the burden of tuberculosis in communities with a high prevalence of HIV have therefore tended to be observational20 or to use proxy outcomes, such as the number of cases found.14
The ZAMSTAR (Zambia, South Africa Tuberculosis and AIDS Reduction) trial was a community-randomised trial of two interventions with the hypothesis that taking interventions beyond health services could significantly reduce the prevalence and transmission of tuberculosis.21 The interventions were embedded within existing health services, applied across a population of about 1 million people, and were assessed with robust measures of the burden of tuberculosis at community level (prevalence of tuberculosis and incidence of tuberculous infection).
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Setting and participants
24 communities in Zambia and the Western Cape province of South Africa were purposively selected such that the tuberculosis notification rate, according to official data, was at least 400 per 100 000 per year, and that each health facility offered tuberculosis diagnosis and treatment to a catchment population of at least 25 000. Population-level HIV data did not exist and therefore we developed a protocol that solicited expert opinion from local and national health officials about each
Results
The trial took place in 24 communities in Zambia (16 communities) and the Western Cape province of South Africa (eight communities; figure 1). The estimated total population in the areas where the intervention was applied (the intervention area) was 962 655, with an average population per community of 40 110. Table 1 shows the results of the randomised allocation and the numbers of individuals who directly participated in the interventions.
Table 2 shows how community-level HIV prevalence varied
Discussion
We assessed prevalence of tuberculosis in 24 communities in Zambia and South Africa, after 3 years of ECF or household interventions for tuberculosis control. Of 64 463 randomly selected individuals, 894 individuals had active tuberculosis. Averaging over 24 communities the geometric mean of tuberculosis prevalence was 832 per 100 000 population. We also measured the incidence of tuberculous infection in a cohort of 8809 children, followed up for a median of 4 years. The adjusted prevalence
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