Toward a molecular microbial blood test for tuberculosis infection.

The World Health Organization's aim to end the global tuberculosis (TB) epidemic by 2050 cannot be achieved without taking measures to identify people with asymptomatic Mycobacterium tuberculosis (Mtb) infection and offer them an intervention to reduce the risk of disease progression, such as preventive antimicrobial therapy. Implementation of this strategy is limited by the fact that existing tests for Mtb infection, which use immunosensitization to Mtb-specific antigens as a proxy for infection, have low positive predictive value for progression to TB. A blood test that detects Mtb deoxyribonucleic acid (DNA) could allow preventive therapy to be targeted at individuals with microbiological evidence of persistent infection. In this review, we summarize recent advances in the development of molecular microbial blood tests for Mtb infection and discuss potential explanations for discordance between their results and those of immunodiagnostic tests in adults with recent exposure to an infectious index case. We also present a roadmap for further development of molecular microbial blood tests for Mtb infection, and highlight the potential for research in this area to provide novel insights into the biology of Mtb infection and yield new tools to support efforts to control the global TB epidemic.