Tuberculosis, Latent (LTBI)

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Description

  • Latent tuberculosis infection (LTBI) is an asymptomatic, noninfectious condition following exposure to an active case of tuberculosis. LTBI is usually detected by a screening skin/blood test. LTBI affects ~25% of the global population.
  • Active tuberculosis (TB) occurs in 5–10% of untreated LTBI patients. Chance of active TB increases with immunosuppression and is highest for all individuals within 2 years of infection; 85% of the cases are pulmonary, which can be spread person-to-person via aerosol route.
  • >80% of active TB cases in the United States result from untreated LTBI.
  • LTBI treatment is a key component of the US TB elimination strategy.
ALERT
  • Nitrosamine particles have been isolated in rifampin and rifapentine products in 2020–2022. They are potential or probable carcinogens- due to the life-threatening nature of TB, the FDA has approved ongoing production of these antimicrobials with close monitoring (1).
  • The current pace of decline in TB incidence will not eliminate TB in the US in the 21st century. Extra effort is needed to identify patients with LTBI (2).

Epidemiology

  • LTBI is not reportable in many states.
  • In the United States, high-risk groups include immigrants from countries with a high TB rate (countries other than Canada, Australia, New Zealand, or a country in western/northern Europe); persons with a history of drug use or homelessness; HIV-infected or immunocompromised individuals; persons living or working in high-risk congregate settings such as nursing homes, carceral facilities, and health care workers (2).
  • Newly exposed individuals (particularly children) are also at higher risk.
  • On average, 5–10% of those infected with LTBI will go on to develop active TB during their lifetime, most typically within 5 years (1)
  • In 2023, there were 9,615 TB cases reported in the United States (3).
  • The highest TB incidence for US-born persons occurred among people of non-Hispanic White race/ethnicity and the most likely medical diagnostic risk factor was a diagnosis of diabetes.
  • Some studies suggest reactivation of LTBI after use of certain immunotherapies, most notably in patients treated for psoriasis (4).

Prevalence

  • Globally, ~2 billion people are estimated to be infected with TB. Globally, ~10 million people were diagnosed with active TB in 2020, ~1.1 million were children.
  • The CDC estimates 13 million people with LTBI (5).

Etiology and Pathophysiology

Mycobacterium tuberculosis, Mycobacterium bovis, and Mycobacterium africanum

Risk Factors

Immigrants from TB-endemic countries, including most countries of Africa, Asia, and Eastern Europe; close contact with infected individual; living or working in a congregate setting; use of illicit drugs; lower socioeconomic status or experiencing homelessness; healthcare workers; laboratory personnel working with mycobacteria

General Prevention

  • Screen for LTBI and treat individuals with positive tests.
  • If a person has fibrotic lung changes on imaging and no evidence of TB treatment, these patients should be screened for LTBI.
  • Special population: Organ donors should be screened. If donor is deceased, interferon-γ release assay (IGRA) testing is still possible.

Commonly Associated Conditions

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