Preventive therapy for latent tuberculosis infection-the promise and the challenges

- Latent tuberculosis infection (LTBI) is an asymptomatic state in which individuals demonstrate an immunological response to Mycobacterium tuberculosis.
- A number of effective regimens are available to treat adults and children with drug-susceptible LTBI.
- The decision to treat individuals with LTBI must carefully balance the risks and benefits to the individual.
- Electronic decision support tools can help clinicians and patients make evidence-based choices.
- Randomized studies to evaluate the effectiveness of regimens to prevent multidrug-resistant TB are underway.
- A substantial scale-up of LTBI screening and treatment will be vital if the global vision of tuberculosis elimination is to be realized.

SummaryAround one third of the world's population may harbour latent tuberculosis infection (LTBI), an asymptomatic immunological state that confers a heightened risk of subsequently developing tuberculosis (TB). Effectively treating LTBI will be essential if the End TB Strategy is to be realized. This review evaluates the evidence in relation to the effectiveness of preventive antibiotic therapy to treat LTBI due to both drug-susceptible and drug-resistant bacteria. Current national and international preventive therapy guidelines are summarized, as well as ongoing randomized trials evaluating regimens to prevent drug-resistant TB. Populations that may benefit most from screening and treatment for LTBI include close contacts of patients with TB (particularly children under 5 years of age) and individuals with substantial immunological impairment. The risks and benefits of treatment must be carefully balanced for each individual. Electronic decision support tools offer one way in which clinicians can help patients to make informed decisions. Modelling studies indicate that the expanded use of preventive therapy will be essential to achieving substantial reductions in the global TB burden. However, the widespread scale-up of screening and treatment will require careful consideration of cost-effectiveness, while ensuring the drivers of ongoing disease transmission are also addressed.