MDR-TB Treatment as Prevention: Modeling the Population-Level Impact of Expanded Treatment for Multidrug-Resistant Tuberculosis

Background: In 2013, approximately 480,000 people developed new active multidrug-resistant tuberculosis (MDR-TB), while only 97,000 people started on treatment for MDR-TB. Individuals with untreated MDR-TB are infectious, but the contribution of insufficient treatment to ongoing epidemic transmission of MDR-TB remains poorly defined.

Methods: We constructed a dynamic transmission model of an MDR-TB epidemic in a representative East/Southeast Asian setting, calibrated using a country (Vietnam) with high-quality TB data. Using approximate Bayesian computation, we investigated a wide array of potential epidemic trajectories consistent with current notification data and known TB epidemiology. Within these data-consistent trajectories, we investigated the impact of improving access to MDR-TB diagnosis and treatment on ten-year projections of MDR-TB incidence and mortality.

Results: Despite an overall projected decline in TB incidence, our data-consistent simulations suggested that MDR-TB incidence would rise by 17% (95% Uncertainty Range [UR] -38% to +137%) between 2015 and 2025 under continued 2013 treatment practices. But if, by 2017, all patients with previously-treated TB could be tested for drug susceptibility, and 85% of those with MDR-TB could be placed on second-line treatment, then our model projects that MDR-TB incidence in 2025 could be reduced by 26% (95% UR 4-52%) relative to projections under continued current practice. If this treatment could be implemented via a novel second-line regimen with similar effectiveness and toxicity as current first-line therapy, a 52% (95% UR 19-72%) reduction in MDR-TB incidence, relative to projections under current practice, could be achieved by 2025. 

Conclusion: Diagnosing and treating MDR-TB reduces transmission and therefore decreases MDR-TB incidence at the population level. Focusing MDR diagnostic efforts on previously-treated cases is an efficient and effective approach. Expansion of diagnosis and treatment should be prioritized as an essential strategy for preventing the spread of MDR-TB.