Langley, Ivor (2016) Impact assessment of new tuberculosis diagnostic tools and algorithms to support policy makers in low and middle income countries : an innovative modelling approach. PhD thesis, University of Warwick.

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Abstract

In many low and middle income countries the infectious disease tuberculosis is a leading and persistent cause of death, sickness and hardship. This is despite an effective and readily available treatment regimen. Better diagnostics and more rapid initiation of patients onto treatment is essential if the high burden of tuberculosis in these settings is to be substantially reduced, as there is currently no effective vaccine. There is an encouraging pipeline of improved diagnostic tools and algorithms being developed, some of which have been endorsed by the World Health Organization (e.g. Xpert MTB/RIF). These new diagnostic tools have the potential to overcome many of the weaknesses of the present processes, however they might substantially increase the demands on scarce resources and funds. In addition, whether these new diagnostics should replace existing methods or be used in combination with them is unclear. Before national tuberculosis programmes can scale-up new diagnostics, policy makers need to understand the effects on patients, the health system, and the wider population. Failure to do so could lead to poor performance outcomes, unsustainable implementation, and wasted resources.

An innovative linked modelling approach is proposed that brings together detailed operational models of patient pathways with transmission models to provide the comprehensive projections required. The studies that make up this research first explore the concept of linked modelling, then in the second study develop a detailed operational model incorporating cost-effectiveness analysis. The third study uses the linked modelling approach to explore eight alternative diagnostic algorithms in Tanzania. It provides comprehensive projections of patient, health system and community impacts including cost-effectiveness analysis, from which the national tuberculosis programme can develop a strategy for scale-up of new diagnostics across the country. Having shown how the approach of linked operational and transmission modelling can assist policy makers, the fourth and fifth studies review the process of impact assessment and recommend how it can be improved, and how the lessons from this research in tuberculosis diagnostics might apply to other health decisions in low and middle income countries.

The linked modelling approach is feasible and relevant in supporting rational decision making for tuberculosis diagnostics in low and middle income countries. The results from using the approach in Tanzania show that full scale-up of Xpert MTB/RIF is a cost-effective option with an incremental cost-effectiveness ratio of US$169 per DALY averted (95% credible interval, 104–265), and has the potential to significantly reduce the national tuberculosis burden. Substantial levels of funding would need to be mobilised to translate this into clinical practice. In the context of Tanzania, targeting Xpert MTB/RIF to HIV-positive patients only, was not cost-effective compared to rollout of LED fluorescence microscopy with two samples collected on the same day. Review of the Impact Assessment Framework and operational modelling used in these studies found the approaches had many other potential applications, for example for decisions around human parasitic disease diagnostics and tuberculosis treatment.

In Tanzania full scale-up of Xpert MTB/RIF should be progressed in districts where resources and funding are available. LED fluorescence microscopy using two samples collected on the same day should be considered in other districts. Tuberculosis programmes should use the operational modelling approach to prioritise the implementation of new diagnostics by district. The operational and linked operational and transmission modelling approaches have many other potential applications in other contexts and disease areas and these should be further researched.

Item Type:	Thesis (PhD)
Subjects:	R Medicine > RC Internal medicine
Library of Congress Subject Headings (LCSH):	Tuberculosis -- Diagnosis., Tuberculosis -- Transmission.
Official Date:	June 2016
Dates:	Date Event June 2016 Submitted
Institution:	University of Warwick
Theses Department:	Warwick Medical School
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Madan, Jason
Sponsors:	United States. Agency for International Development; International Union against Tuberculosis and Lung Disease
Format of File:	pdf
Extent:	53 leaves : illustrations, charts, maps
Language:	eng

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