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Thibela TB: Community-wide IPT did not improve TB control in South Africa’s mines at the population level
Theo Smart, 2012-03-15 14:50:00
Giving a six- to nine-month course of isoniazid preventive therapy (IPT) at a ‘community-wide level’ – to everyone working at randomly selected South African gold mines – had no effect on TB incidence, TB prevalence or all-cause mortality in the population, when compared to a cluster of gold mines randomised to standard TB programme management, according to the ‘Thibela TB’ study, the largest IPT intervention study ever to be conducted.
The results, released during a late-breaker presentation on the final day of the 19th Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle, are clearly disappointing given the extremely high burden of tuberculosis (TB) facing workers in the mines of South Africa, where there is also a high prevalence of HIV co-infection – and had investigators scrambling to provide an explanation, which may involve inadequate uptake and adherence in the study.
However, part of the explanation could have been uncovered in a post-hoc analysis, described in a subsequent presentation, which found that IPT did have an effect at the individual level – reducing TB while people were taking it – but this effect was lost very quickly once IPT was stopped; suggesting that levels of TB transmission in the mining communities may be higher than realised – and that a longer, potentially continuous course may be necessary to better control TB.
“We are working to better understand the reasons for these results so that we can make recommendations to improve TB control in the mines,” said lead investigator Professor Gavin Churchyard, of the Aurum Institute in South Africa, and the London School of Hygiene and Tropical Medicine.
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