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U.S. Department of Health and Human Services


TB Facts for Health Care Workers

Prevention of Tuberculosis

The main purpose of treating LTBI is to prevent it from progressing to clinically active TB disease. Therefore, persons with positive tuberculin skin test results who do not have clinically active disease should be evaluated for treatment of LTBI.

Candidates for Treatment of Latent TB Infection

Persons in the following high-risk groups should be considered for treatment of LTBI if their reaction to the tuberculin skin test is >5 mm of induration:

  • Persons with HIV infection *
  • Close contacts of a TB case*
  • Patients who have had organ transplants, and other immunosuppressed patients (receiving the equivalent of >15 mg/day of prednisone for >1 month)
  • Persons with fibrotic changes on chest radiograph consistent with old TB disease
  • Persons receiving specialized treatment for rheumatoid arthritis or Crohn’s disease

Persons in the following high-risk groups should be considered for treatment of LTBI if their reaction to the tuberculin skin test is >10 mm of induration:

  • Recent arrivals to the United States (<5 years) from high-prevalence countries
  • Persons who inject illicit drugs
  • Residents and employees of high-risk congregate settings
  • Mycobacteriology laboratory personnel
  • Persons with medical conditions that make them high risk (see Table 1, "Summary of interpretation of tuberculin skin-test results")
  • Children <4 years of age, or children and adolescents exposed to adults in high-risk categories

In general, persons with no known risk factors for TB should not be tested for LTBI. However, testing is occasionally performed among certain population groups for surveillance purposes or where a case of TB could result in extensive transmission. If testing is performed in these populations, they may be considered for treatment of LTBI if their reaction to the tuberculin test is >15 mm of induration. This group should be given a lower priority for prevention efforts than the groups listed previously.

*In some circumstances, persons in these categories may be evaluated for the treatment for LTBI in the absence of a positive TST. Treatment for LTBI should be given after TB disease has been ruled out. Some close contacts who have a negative tuberculin skin test reaction (< 5 mm of induration) should be evaluated for treatment of LTBI. These contacts include children less than 5 years of age, immunosuppressed people, and others who may develop TB disease quickly after infection.

Close contacts who have a negative reaction to an initial skin test should be retested 8 to 10 weeks after they were last exposed to TB. If receiving treatment for LTBI, treatment may be discontinued if the skin test result is again negative and if the person is no longer exposed to TB.

However, close contacts known to have or suspected of having HIV infection and other immunocompromised persons should be given treatment for LTBI regardless of their skin test reaction.

Because of their age, infants and young children with a positive skin test are known to have been infected recently, and are at high risk of their infection progressing to disease. Infants and young children are also more likely than older children and adults to develop life-threatening forms of TB disease.

Children <5 years of age who are close contacts to someone with infectious TB should receive treatment for LTBI even if the tuberculin skin test result and chest radiograph do not suggest TB. A second tuberculin test should be placed 8–10 weeks after the last exposure to infectious TB. Treatment of LTBI can be discontinued at that time if all of the following conditions are met:

  • The second tuberculin test is negative.
  • The second test was performed at least 10 weeks after the child was last exposed to infectious TB.
  • The child is at least 6 months of age.

Regimens for the Treatment of Latent TB Infection

For persons suspected of having LTBI, treatment of LTBI should not begin until TB disease has been excluded. Persons suspected of having TB disease should receive the recommended multidrug regimen for treatment of disease until the diagnosis is confirmed or ruled out.

Although regimens are broadly applicable, there are modifications that should be considered under special circumstances (i.e., HIV infection, suspected drug resistance, pregnancy, or treatment of children). Listed in Table 2 are the regimens; please refer to Targeted Tuberculin Testing and Treatment of Latent TB Infection for detailed information for the treatment of LTBI.

Table 2: Drug Regimens for the Treatment of LTBI


Duration (months)

Dosing Frequency

Minimum Doses





Twice Weekly






Twice Weekly







Generally should not be offered for treatment of LTBI

Owing to the reports of severe liver injury and deaths, CDC and ATS now recommend that the combination of rifampin (RIF) and pyrazinamide (PZA) should generally not be offered for the treatment of LTBI. If the potential benefits substantially outweigh the demonstrated risk of severe liver injury and death associated with this regimen and the patient has no contraindications, a TB/LTBI expert should be consulted prior to the use of this regimen. (Clinicians should continue the appropriate use of RIF and PZA in multidrug regimens for the treatment of TB disease.)


Isoniazid (INH) or Rifampin Alone
Routine laboratory monitoring during treatment of LTBI is indicated only for those whose baseline tests suggest a liver disorder and for other persons with a risk of hepatic disease. Laboratory testing should be performed to evaluate possible adverse reactions that occur during the treatment regimen.

Rifampin/Pyrazinamide or Rifabutin/Pyrazinamide
A TB/LTBI expert should be consulted prior to the use of this regimen.

CDC is collecting reports of severe adverse events (i.e., leading to hospital admission or death) in persons receiving any treatment regimen for LTBI. Report possible cases to the Division of Tuberculosis Elimination by calling (404) 639-8401 or by e-mail to

To ensure that persons in high-risk groups adhere to therapy, INH can be given twice weekly at a dosage of 15 mg/kg, up to a maximum of 900 mg, using directly observed therapy (DOT) of LTBI. DOT refers to the observation by a health care provider of patients as they ingest anti-TB medications.

The method of DOT of LTBI should be based on a thorough assessment of each patient’s needs, living and employment conditions, and preferences. The patient and provider should agree on a method that ensures the best possible DOT of LTBI routine and that maintains the patient’s confidentiality.

Situations in which patients not receiving DOT for LTBI miss appointments or demonstrate other nonadherent behavior should be brought to the attention of the appropriate public health officials. These patients should be considered for DOT of LTBI.

Persons given treatment for LTBI should be monitored monthly for drug side effects, especially signs and symptoms of hepatitis.


Released October 2008
Centers for Disease Control and Prevention
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Division of Tuberculosis Elimination -

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