Optimizing TB policies using the global TB portfolio model: an economic analysis.

Rationale: Tuberculosis (TB) remains a global health crisis, disproportionately affecting low- and middle-income countries. Strategic resource allocation is essential to achieving the WHO End TB targets. Existing TB costing tools have limitations in conducting global analyses, prompting the development of a novel model tailored to address these gaps. Methods: We developed a new, open-source TB costing model that simulates detailed TB care cascades comprising steps of screening, diagnosis, treatment, and prevention for those eligible - according to WHO guidelines for 20 distinct population groups. These include 10 groups each from patient-initiated and provider-initiated pathways, capturing variations in pulmonary status, age, HIV/ART status, and drug sensitivity. The model captures the cost of a large-scale vaccine. We demonstrate the model's functionality through a case study that informed the Global Fund's Investment Case for its 8th replenishment (2027-2029). Results: In the case study, the model was first used to estimate the cost of implementing the TB Global Plan 2023 - 2030. This scenario incorporated intervention targets, normative standards of care, and the availability of new TB tools. An optimization routine applied to 29 high-burden countries estimated maximal TB impact under constrained funding scenarios. The results were also used to assess the potential impact and contribution of innovation within the Global Fund's 8th replenishment. Discussion: This new TB costing model offers improved representation of TB care complexity across diverse populations, with enhanced transparency, flexibility, and policy relevance. Its application in global TB strategy analysis highlights its value in informing investment cases and prioritizing interventions for maximal impact under resource constraints.