This project will give practical guidance and allow for simplification of algorithms so that more programmatic approaches to TB contact tracing can be easily implemented and improve progress towards finding the millions with active TB that are missed by routine or passive case detection. Robust interventions would include better diagnostics and better strategies for active case finding among those exposed to TB in the community.
People sharing a household with a person diagnosed with active TB are at an increased risk of developing TB in the subsequent 2 years. Household contact tracing is thus a crucial intervention for realizing elimination of TB but is underutilised in high-burden countries, often with under-resourced health systems that are also dealing with competing priorities. Interventions directed at households would provide a platform for interventions aimed at curbing transmission. Currently, although recommended, TB contact tracing is poorly implemented and has not gained traction in the TB response in these countries.
The project will demonstrate the effectiveness of the recent WHO guidance to expand prevention to all household contacts of a person with active TB regardless of age or HIV infection. This recent guideline allows national TB programmes the opportunity to reach more millions with TB preventive treatment and halt the progression from infection to active TB disease. Each year, approximately 1.5 million household contacts are eligible for preventive treatment in Lesotho, South Africa, and Tanzania. If the strategy proposed in CUT-TB is demonstrated to be successful, national and WHO policy would change to possibly impact as many lives as possible in these countries alone. This would directly impact on population-level transmission of TB. We will further demonstrate this through mathematical modelling of results thus obtaining wider advocacy.
Change in clinical practice: The standard approach employed in contact tracing is symptomatic screening followed by sputum testing using either GeneXpert MTB/RIF (Xpert) or sputum smear microscopy in those who are symptom positive. The number of symptom-positive individuals identified is fairly heterogeneous and can range between 18%- 35%, the subsequent yield of TB is commensurately low and often dependent on the rigour of screening methods. We have proposed to evaluate a strategy that advocates universal testing of contacts using Xpert that is independent of symptoms.
We envisage this will increase the numbers reached for active screening, the yield of undiagnosed TB and Xpert negative individuals for subsequent TB preventive treatment (TPT), whilst also simplifying algorithms for contact screening. Similarly, among children, the standard algorithm of TST testing and then sputum induction to diagnose TB has been shown to be effective, but it is also not followed routinely and very difficult to implement.
Globally, only 292182 children started preventive treatment in 2017, representing 23% of all children estimated to have been eligible, this despite eligibility being restricted to children <5 years.
Recent changes in eligibility criteria for preventive therapy, necessitates stronger mechanisms to facilitate uptake. The introduction of simpler screening algorithms to identify undiagnosed TB at household level would maximize its impact, but also allow for easier implementation by routine programmes.