Tuberculosis, Latent (LTBI)

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Basics

Description

  • Latent tuberculosis infection (LTBI) is an asymptomatic, noninfectious condition following exposure to an active case of tuberculosis. LTBI is usually detected by a positive skin test (i.e., purified protein derivative [PPD]) or a positive interferon-γ release assay (IGRA) test.
  • Active TB occurs in 5–10% of infected individuals who have not received preventive therapy. 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 is capable of person-to-person spread via aerosol route.
  • Greater than 80% of TB cases in United States result from untreated LTBI (1).
  • LTBI treatment is a key component of the TB elimination strategy for the United States.

ALERT
The current pace of decline in TB incidence will not eliminate TB in the United States in the 21st century. Extra effort is needed to identify patients with LTBI (2).

Epidemiology

  • In the United States, high-risk groups include immigrants from Asia, Latin America, Africa, and the Pacific basin; blacks; homeless persons; persons with a history of drug use or history of incarceration; HIV-infected individuals; and health care workers and other immunocompromised individuals (2).
  • TB is a major cause of death in individuals infected with HIV (2).
  • Newly exposed (particularly children) are also at high risk.
  • In 2018, there were 9,029 new tuberculosis (TB) cases reported in the United States, a 0.7% decrease from 2017 (1).
  • Among the 9,029 TB cases reported in the United States in 2018, approximately two thirds (6,276 [69.5%]) occurred in non–U.S.-born persons, whereas 2,662 (29.5%) occurred in U.S.-born persons; 91 (1.0%) cases occurred in persons for whom no national origin was documented (1).
  • Among non–U.S.-born persons with TB, incidence in 2018 was highest among Asians, followed by Native Hawaiians/Pacific Islanders, non-Hispanic blacks, Hispanics, and American Indian/Alaska Natives, and was lowest among non-Hispanic whites (1,2).
  • The highest TB incidence for U.S.-born persons occurred among Native Hawaiians/Pacific Islanders, followed by American Indians/Alaska Natives, blacks, Asians, and Hispanics, and was lowest in whites (1).

Incidence
In 2018, a total of 9,029 new tuberculosis (TB) cases were reported in the United States (1).

Prevalence
  • 13 million people in the United States are infected with TB (1)
  • ~1/4 of the world’s population harbors latent TB.

Etiology and Pathophysiology

Mycobacterium tuberculosis, Mycobacterium bovis, and Mycobacterium africanum

Risk Factors

  • HIV infection, immunosuppression
  • Immigrants (from Asia, Latin America, Pacific Islands, Africa, or areas with high rates of TB), including migrant workers
  • Close contact with infected individual
  • Institutionalization (e.g., prison, nursing home)
  • Use of illicit drugs
  • Lower socioeconomic or homeless status
  • Health care workers
  • Chronic medical disease such as diabetes mellitus (DM), end-stage renal disease, cancer, or silicosis; organ transplant (immunosuppression)
  • Persons with fibrotic changes on chest x-ray (CXR) consistent with previous TB infection
  • Recent TB skin test (tuberculin skin test [TST]) converters
  • Laboratory personnel working with mycobacteria
  • Organ donors should be screened. If donor is deceased, IGRA testing is still possible.

General Prevention

Screen for LTBI and treat individuals with positive tests.

Commonly Associated Conditions

  • HIV infection (see “Initial Tests (lab, imaging)”)
  • Immunosuppression

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Basics

Description

  • Latent tuberculosis infection (LTBI) is an asymptomatic, noninfectious condition following exposure to an active case of tuberculosis. LTBI is usually detected by a positive skin test (i.e., purified protein derivative [PPD]) or a positive interferon-γ release assay (IGRA) test.
  • Active TB occurs in 5–10% of infected individuals who have not received preventive therapy. 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 is capable of person-to-person spread via aerosol route.
  • Greater than 80% of TB cases in United States result from untreated LTBI (1).
  • LTBI treatment is a key component of the TB elimination strategy for the United States.

ALERT
The current pace of decline in TB incidence will not eliminate TB in the United States in the 21st century. Extra effort is needed to identify patients with LTBI (2).

Epidemiology

  • In the United States, high-risk groups include immigrants from Asia, Latin America, Africa, and the Pacific basin; blacks; homeless persons; persons with a history of drug use or history of incarceration; HIV-infected individuals; and health care workers and other immunocompromised individuals (2).
  • TB is a major cause of death in individuals infected with HIV (2).
  • Newly exposed (particularly children) are also at high risk.
  • In 2018, there were 9,029 new tuberculosis (TB) cases reported in the United States, a 0.7% decrease from 2017 (1).
  • Among the 9,029 TB cases reported in the United States in 2018, approximately two thirds (6,276 [69.5%]) occurred in non–U.S.-born persons, whereas 2,662 (29.5%) occurred in U.S.-born persons; 91 (1.0%) cases occurred in persons for whom no national origin was documented (1).
  • Among non–U.S.-born persons with TB, incidence in 2018 was highest among Asians, followed by Native Hawaiians/Pacific Islanders, non-Hispanic blacks, Hispanics, and American Indian/Alaska Natives, and was lowest among non-Hispanic whites (1,2).
  • The highest TB incidence for U.S.-born persons occurred among Native Hawaiians/Pacific Islanders, followed by American Indians/Alaska Natives, blacks, Asians, and Hispanics, and was lowest in whites (1).

Incidence
In 2018, a total of 9,029 new tuberculosis (TB) cases were reported in the United States (1).

Prevalence
  • 13 million people in the United States are infected with TB (1)
  • ~1/4 of the world’s population harbors latent TB.

Etiology and Pathophysiology

Mycobacterium tuberculosis, Mycobacterium bovis, and Mycobacterium africanum

Risk Factors

  • HIV infection, immunosuppression
  • Immigrants (from Asia, Latin America, Pacific Islands, Africa, or areas with high rates of TB), including migrant workers
  • Close contact with infected individual
  • Institutionalization (e.g., prison, nursing home)
  • Use of illicit drugs
  • Lower socioeconomic or homeless status
  • Health care workers
  • Chronic medical disease such as diabetes mellitus (DM), end-stage renal disease, cancer, or silicosis; organ transplant (immunosuppression)
  • Persons with fibrotic changes on chest x-ray (CXR) consistent with previous TB infection
  • Recent TB skin test (tuberculin skin test [TST]) converters
  • Laboratory personnel working with mycobacteria
  • Organ donors should be screened. If donor is deceased, IGRA testing is still possible.

General Prevention

Screen for LTBI and treat individuals with positive tests.

Commonly Associated Conditions

  • HIV infection (see “Initial Tests (lab, imaging)”)
  • Immunosuppression

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