Guidelines for Tuberculin Skin Test Screening and Treatment of Latent TB Infection



Why screen for tuberculosis?

The goal of screening programs is to identify persons with latent TB infection (LTBI) who are at high risk for progressing to active disease and would benefit from treatment, or to find persons who have clinical TB disease and need treatment.

Who should be screened for TB?

The following groups should be screened with the tuberculin skin test: 

  • Close contacts of persons known or suspected to have TB, i.e. those sharing the same household or other enclosed environments
  • Persons infected with HIV
  • Persons who have certain clinical conditions known to increase the risk for disease if infection occurs
  • Persons with a history of inadequately treated TB
  • Persons who inject illicit drugs
  • Residents and employees of high-risk congregate settings (i.e. nursing homes, correctional facilities, mental institutions, other long-term care facilities, and homeless shelters)
  • Health-care workers who serve high-risk clients
  • Persons born outside the U.S. and Canada, including children. Prior vaccination with BCG is not a contraindication for testing, nor does it affect the treatment protocol.
  • Some medically underserved, low-income populations, including high-risk racial and ethnic groups
  • Infants, children, and adolescents exposed to adults in high-risk categories
  • Locally defined high prevalence groups (substance abusers, migrant workers, the homeless)

 Who should not be routinely screened with the tuberculin skin test?

The following are examples of groups who do not need to be screened routinely for TB unless one or more of the above risk factors are present: 

  • School children and day care attendees
  • Foreign-born persons living in the U.S. for more than 5 years who have been screened previously
  • Pregnant women
  • Food handlers

Why limit tuberculin screening to just high-risk individuals?

  • Targeted screening allows resources to be directed at the two top priorities of TB control: treatment of active TB cases and conducting thorough contact investigations.
  • The tuberculin skin test is a better test when its use is restricted to high-risk individuals. There are fewer false positives, which means less money is spent on unnecessary diagnostic evaluation and treatment.
  • School-based screening for TB among children was started in the 1950’s when infection and disease rates were higher than at the present time.
  • Broad-based school testing involves screening large numbers of low-risk children and the majority of children who have TB are preschool age.
  • Generalized screening of school children as a public health measure is not a cost-effective method of detecting or preventing cases of childhood TB and should be discontinued.

Who should receive treatment for LTBI?

Regardless of age, persons who fall into one or more of the following high-risk categories with a positive skin test, and who have not previously received treatment, should be treated unless contraindicated (see below):

  • close contacts of a person with infectious TB (TST considered positive with ³ 5mm induration)
  • persons with HIV infection (TST considered positive with ³ 5mm induration)
  • organ transplant patients, or patients with other immunosuppressive disorders (TST considered positive with ³ 5mm induration)
  • persons whose chest x-ray shows stable fibrotic lesions consistent with old, healed MTB and a history of inadequately treated TB or no prior history of treatment for TB (TST considered positive with ³ 5mm induration)
  • injection drug users
  • persons with clinical conditions that make them high-risk, e.g. diabetes mellitus, certain forms of cancer, silicosis, end-stage renal disease, substance abusers
  • recent tuberculin skin test converters (³10mm increase within the past two years)
  • persons born in countries where TB is common
  • mycobacteriology laboratory personnel
  • residents and employees of high-risk congregate settings
  • children younger than 4 years of age
  • children and adolescents exposed to adults in high-risk groups
  • persons with recent travel to an area with high rates of TB

Some contacts to infectious TB cases have medical conditions that increase their risk of progression to active disease if they are infected. Persons with high-risk medical conditions (e.g., HIV +, children < 4 years of age, immunosuppression) who have had active disease ruled out but whose initial TST is < 5 mm of induration, should be placed on treatment for LTBI until LTBI is ruled out. If a second TST placed 10 weeks after last contact with the source case is still < 5 mm, treatment may be stopped. If it is ³ 5 mm, continue the full course of treatment.

What is the recommended treatment regimen for LTBI?

Isoniazid for 9 months, regardless of age or HIV status, is the preferred regimen. Isoniazid may be given to HIV-negative adults for 6 months if treatment for 9 months is not possible. PZA and rifampin for 2 or 3 months for adults only is no longer recommended for general use due to an unacceptably high risk of hepatitis. Consult with a TB expert before prescribing this regimen. Rifampin for 4 months for adults or 6 months for children is an alternate regimen that may be prescribed in certain circumstances, such as exposure to an isoniazid-resistant case. Dosages for all regimens are the same as for active disease. The alternate short-course regimens are strictly second-line recommendations and should not be used routinely in place of the isoniazid regimens.

  • persons with active hepatitis
  • persons with end-stage liver disease
  • pregnancy (therapy is usually delayed until after delivery)
  • major adverse medication reactions
  • previous adequate treatment for LTBI or active disease

What are the current standards for the evaluation and monitoring of treatment (LTBI)?

  • Baseline laboratory testing is not routinely indicated for all patients at the start of treatment for LTBI.
  • Recent data indicate that baseline testing is no longer routinely indicated in persons older than 35 years of age.
  • Once patients have been identified as requiring treatment for LTBI, they should receive an initial clinical evaluation. This evaluation should include a detailed history for risk factors that increase the likelihood of hepatotoxicity[1] and a brief physical assessment checking for signs of hepatitis.
  • Patients whose initial evaluation suggests these risk factors should have baseline hepatic measurements of serum AST (SGOT) or ALT (SGPT) and bilirubin. 
  • Patients should be educated about the side effects associated with treatment of LTBI and advised to promptly seek medical evaluation when they occur.
  • Patients being treated for LTBI should also receive follow-up evaluations at least monthly. This evaluation should consist of questioning about side effects and a brief physical assessment checking for signs of hepatitis.

What radiographic evaluations are indicated in the workup of patients with suspected LTBI?

  • A chest radiograph is indicated for all persons being considered for treatment of LTBI to exclude active pulmonary TB. Children younger than 5 yr of age should have both posterior–anterior and lateral radiographs. All other persons should receive posterior–anterior radiographs. 
  • Patients with questionable findings on initial radiographs should be evaluated with alternative x-ray views (lateral, apical lordotic, obliques).
  • If these views do not resolve visualization of any questionable areas on initial radiographs, a CT scan can be considered. (Normally, there is little to no indication for the use of CT scans of the chest. CT scans often are indicated for other purposes, but that would not be considered part of the LTBI workup.)
  • For persons with LTBI who have had active disease ruled out and for asymptomatic tuberculosis patients who have completed treatment, repeat chest x-ray examinations have been shown to be of insufficient clinical value or productivity to justify their continued use and are not recommended unless specific medical conditions exist.

In summary, efficient screening programs are limited to high-risk persons who would benefit from treatment for latent TB infection.

This statement was approved by the Indiana State Department of Health TB Medical Advisory Board on March 24, 1997, and revised October 25, 2000 and October 27, 2004.

  • previous adverse reactions to drugs contemplated for treatment of LTBI
  • current use of drugs which may interact with the drugs used for treatment
  • patients infected with HIV
  • pregnant women and those in the immediate postpartum period (i.e., within 3 months of delivery)
  • persons with a history of liver disease (e.g., hepatitis B or C, alcoholic hepatitis or cirrhosis)
  • persons who use alcohol regularly
  • persons at risk for chronic liver disease
  • signs of hepatitis on physical assessment