Modelling tuberculosis control priorities: more of the same will not do – Authors’ reply

The tuberculosis care cascade is only one part of a much broader picture of tuberculosis control, a picture that involves prevention as well as cure, underpinned by a broader understanding of the determinants of tuberculosis.1Reid MJA Arinaminpathy N Bloom A et al.Building a tuberculosis-free world: The Lancet Commission on tuberculosis.Lancet. 2019; 393: 1331-1384Summary Full Text Full Text PDF PubMed Scopus (146) Google Scholar We thank Christian Wejse and colleagues for their Correspondence, and they raise an important point about the key role that tuberculosis prevention will need to play in tuberculosis control. We agree with their point, although the focus of our work is on the care cascade. Indeed, supplementary results in the appendix show how the care cascade alone will not be sufficient to eliminate tuberculosis as a public health problem. Nonetheless, this point is one worth reiterating. Wejse and colleagues also point out that the levels of coverage modelled in our analysis are not practically feasible. We note here that assessing current interventions is a substantial task that many previous analyses have already addressed.2Houben RMGJ Menzies NA Sumner T et al.Feasibility of achieving the 2025 WHO global tuberculosis targets in South Africa, China, and India: a combined analysis of 11 mathematical models.Lancet Glob Health. 2016; 4: e806-e815Summary Full Text Full Text PDF PubMed Scopus (100) Google Scholar, 3Kendall EA Schumacher SG Denkinger CM Dowdy DW Estimated clinical impact of the Xpert MTB/RIF Ultra cartridge for diagnosis of pulmonary tuberculosis: a modeling study.PLoS Med. 2017; 14e1002472Crossref PubMed Scopus (36) Google Scholar In our study, rather than what is feasible with current tools, our focus was on the strength and type of effect on the care cascade that should be demanded from future interventions on the care cascade. The analogy of population-attributable fractions can be helpful, as an example of an analytical approach that makes infeasible assumptions (imagining the complete removal of a risk factor from a population), to yield useful insights (the quantitative comparison of different factors for a given disease burden). For all their limitations, a key strength of mathematical models is their flexibility and their ability to be applied in a similar way across different scenarios. Although future tuberculosis control will require the intensified use of current tools, it will also demand innovations that can open qualitatively new approaches in the global tuberculosis response. We agree with Wejse and colleagues that preventive therapy would form an important part of this response. As forcefully argued in The Lancet Commission on tuberculosis,1Reid MJA Arinaminpathy N Bloom A et al.Building a tuberculosis-free world: The Lancet Commission on tuberculosis.Lancet. 2019; 393: 1331-1384Summary Full Text Full Text PDF PubMed Scopus (146) Google Scholar all such measures need to go hand-in-hand with improvements in basic tuberculosis services to achieve the greatest possible reductions in tuberculosis burden. We declare no competing interests. Assessing tuberculosis control priorities in high-burden settings: a modelling approachLinked to transmission, the care cascade can be valuable, not only for improving patient outcomes but also in identifying and monitoring programmatic priorities to reduce tuberculosis incidence and mortality. Full-Text PDF Open AccessModelling tuberculosis control priorities: more of the same will not doIn The Lancet Global Health, Juan F Vesga and colleagues1 reported on their assessment of tuberculosis control priorities in high-burden settings using a robust and well accepted modelling approach with a focus on what can be achieved by strengthening the tuberculosis cascade of care. The authors concluded that closing gaps and decreasing delays in the cascade of care will be valuable for improving patient outcomes and identifying programmatic priorities, and although their results were robust, their assumptions on the extent of reductions in gaps in the cascade of care were unrealistic. Full-Text PDF Open Access