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Preventing new TB cases by treating household members

Treating members of a household known to be infected with tuberculosis could prevent more new cases than screening and treating the community at large, according to an analysis led by a University of Michigan researcher. Medical Xpress reports that the analysis looked at households in 106 public health centres in Lima, Peru, between 2009 and 2012, as part of a study led by researchers at Harvard University and Socios En Salud (Peru). The centres serve an estimated 3.3m people.

The researchers showed that treating household contacts of those known to be infected with TB could prevent as many as four times as many TB cases on a per-treatment basis than by screening and providing treatment in the community at large.

"Our analysis suggests that targeting screening and treatment on people with household exposure to TB would prevent more cases on a per-screening basis than untargeted community-wide efforts," said Jon Zelner, assistant professor of epidemiology at U-M's School of Public Health. "It suggests that these efforts are worth trying in urban settings like Lima, which has a high incidence of TB and low HIV prevalence. We should be looking at this as an approach in other similar contexts."

According to the World Health Organisation, TB is one of the top 10 causes of deaths worldwide. In 2015, 10.4m people fell ill with tuberculosis and 1.8m died from the disease. According to WHO, over 95% of tuberculosis deaths occur in low- and middle-income countries. Six countries account for 60% of the total cases of TB, with India leading the count, followed by Indonesia, China, Nigeria, Pakistan and South Africa.

Progress to control the disease is not keeping up to meet the goals of reducing TB-related deaths by 80% by 2030, the researchers say, adding that improving current tools to identify cases more promptly to interrupt future transmission is a critical step towards accomplishing these goals.

Background: Untargeted active screening and treatment programmes for tuberculosis (TB) have not been shown to be more effective than passive screening and isoniazid preventive therapy (IPT) for reducing TB incidence. In this manuscript, we compare the efficacy of targeting screening and IPT on high-risk household contacts of diagnosed TB cases, with less-targeted active screening approaches in Lima, Peru.
Methods: We conducted a population-based prospective cohort study within households of TB cases in Lima. We identified all adults diagnosed with incident pulmonary TB from 2009 through 2012 at 106 participating public health centres (HC) within our catchment area of ∼3.3 million inhabitants. We estimated combined effects of community and household exposure on the risk of latent TB infection (LTBI) and incident TB disease. We used simulation modelling to assess the efficacy of TB screening programmes for reducing the risk of incident TB in these contacts.
Results: Individuals with household exposure to TB are more likely to present with LTBI and TB disease than those without this exposure, despite wide variation in community exposure. Simulations suggest that more cases are prevented by 1000 administrations of IPT to tuberculin skin test (TST)-positive household contacts of identified TB cases (30, 95% CI = 16,47) than from blanket screening and treatment in the community (7, 95% CI = 2,17).
Conclusions: Household exposure remains a major driver of incident TB risk among household contacts of identified TB cases. Targeting interventions on these individuals is likely to prevent more cases of TB than blanket screening of individuals in the community.

Jon Zelner, Megan Murray, Mercedes Becerra, Jerome Galea, Leonid Lecca, Roger Calderon, Rosa Yataco, Ted Cohen

[link url="https://medicalxpress.com/news/2017-10-curb-tb-infections-low-income-low-hiv.html"]Medical Xpress report[/link]
[link url="https://academic.oup.com/ije/article-abstract/doi/10.1093/ije/dyx171/4157904/Protective-effects-of-household-based-TB?redirectedFrom=fulltext"]International Journal of Epidemiology abstract[/link]

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