Infectious diseases

TB rates drop with active screening


Australian funded and supported research in Vietnam has demonstrated that active community-wide screening can substantially reduce the prevalence of tuberculosis in areas with a high burden of disease.

The findings, published in the New England Journal of Medicine, support the implementation of active screening and case finding in order to substantially accelerate progress toward the WHO goal of tuberculosis elimination.

The Active Case Finding for Tuberculosis 3 (ACT3) study compared active screening performed annually for three years in more than 42,000 participants from about 60 villages or suburbs, with no intervention in similar sized communities.

In the control communities, screening was only conducted in people presenting with symptoms to the local TB clinics.

All participants who were diagnosed with tuberculosis in either group were treated according to the national TB program policy.

The study found the prevalence ratio for microbiologically confirmed TB in the intervention group during a fourth year of the study was 0.56 in comparison to the control group.

“The number of persons needed to have been screened annually for 3 years to prevent one prevalent case of tuberculosis in the fourth year was 1002,” the researchers said.

The study, led by Professor Guy Marks from the Woolcock Institute of Medical Research, said the rate of decline in TB prevalence in the study was nearly 15% per annum – considerably higher than the current worldwide rate of decline of about 2% as estimated by the WHO.

While the prevalence of TB was not found to be lower in children born 1-2 years before the intervention compared to controls, a post hoc analysis of older children 3-10 years of age in the first year of the intervention found the prevalence ratio was 0.50 in the intervention group compared to the controls.

“The difference in findings between these two age cohorts implies that the older children, but not the younger children, benefited from reduced transmission consequent to the reduced prevalence of tuberculosis among persons 15 years of age or older.”

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