The potential impact of enhanced diagnostic techniques for tuberculosis driven by HIV: a mathematical model

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Abstract
Objective: To explore the potential impact of enhanced tuberculosis (TB) diagnostic techniques as a TB control strategy in an adult population with high HIV prevalence. Design: A compartmental difference-equation model of TB/HIV was developed using parameter estimates from the literature. Methods: The impact of five TB control interventions (rapid molecular testing, mycobacterial culture, community-wide and HIV-targeted active case finding, and highly active antiretroviral therapy) on TB incidence, prevalence, and mortality was modeled in a steady-state population with an HIV prevalence of 17% and annual TB incidence of 409 per 100 000. Sensitivity analyses assessed the influence of each model parameter on the interventions’ mortality impact. Results: Enhanced diagnostic techniques (rapid molecular testing or culture) are each projected to reduce TB prevalence and mortality by 20% or more, an impact similar to that of active case-finding in 33% of the general community and greater than the effect achievable by case-finding or antiretroviral treatment efforts in HIV-positive patients alone. The projected impact of enhanced diagnostics on TB incidence (< 10% reduction) is smaller. The impact of TB diagnostics is sensitive to the quality of existing diagnostic standards and the level of access to diagnostic services, but is robust across a wide range of population parameters including HIV and TB incidence. Conclusions: Enhanced TB diagnostic techniques may have substantial impact on TB morbidity and mortality in HIV-endemic regions. As TB rates continue to increase in these areas, enhanced diagnostic techniques merit further consideration as TB control strategies.