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Tuberculin Skin Test

Report offers recommendations for diagnosis, treatment of tuberculosis infection

November 29, 2021

A healthy 7-year-old who was adopted from a tuberculosis (TB)-endemic country has a routine well-child visit. The parents have no concerns about growth or development. The physical exam reveals a well-healed bacillus Calmette-Guérin (BCG) scar in the child’s right deltoid region. A screening tuberculin skin test (TST) shows induration at 8 millimeters (mm).

Question: What are the next steps in diagnostic interventions?

Answer: TB testing should not be performed in the absence of clinical concern or epidemiologic risks. This TST result likely represents cross-reaction to BCG vaccine. As a follow-up test, an interferon-gamma release assay (IGRA) is recommended, as there is little cross-reactivity with BCG.

A 16-year-old is a household contact of a person with TB disease. The induration of the TST is 20 mm. The physical exam and a two-view chest radiograph are normal.

Question: What therapeutic interventions are recommended?

Answer: This patient has tuberculosis infection (TBI, formerly called latent TB infection). The purpose of treating TBI is to decrease the risk of progression to disease. The medical practitioner should be aware of several well-tolerated and safe drug regimens for TBI.

TB remains an important problem in the pediatric population, and medical practitioners are faced with questions regarding interpretation of test results and what treatment regimens are safe and effective.

A new AAP clinical report provides updated recommendations for diagnosis and treatment of TBI in children and adolescents. Tuberculosis Infection in Children and Adolescents: Testing and Treatment, from the Committee on Infectious Diseases, is available at and will be published in the December issue of Pediatrics.

Change in terminology

A variety of outcomes may occur for an individual who encounters the tuberculosis bacilli. Infection may be followed by rapid progression to symptomatic disease or by immune control of the bacilli; the latter may be lost due to aging or immune-compromising conditions.

Under immune control, the bacilli are viable and not viewed as dormant or latent. Removal of the term “latent” better represents the pathogenesis of tuberculosis and will reduce confusion when discussing treatment goals with patients and families.

The clinical report uses the term tuberculosis infection (TBI) when describing individuals who are infected (as evidenced with a positive TST or IGRA), asymptomatic and have a chest radiograph without findings for active TB disease.

Mycobacterium tuberculosis
Scanning electron micrograph of Mycobacterium tuberculosis. Courtesy of
the National Institute of Allergy and Infectious Diseases













The first part of the report describes the available tests for TB and their interpretation. The TST has been used historically for diagnosis of TB infection and disease. Logistical problems (appropriate placement, interpretation, need for return visit) may make this test undesirable for medical staff, patients and families.

Data and experience in using IGRAs are increasing, including in children as young as 2 years. Although more expensive than the TST, IGRAs may be more cost-effective because of time savings and the elimination of many false-positive results. The report describes how medical practitioners can strategize their use in several scenarios, including close investigation of active TB cases, in immunocompromised individuals or in those with a history of BCG vaccination.

Treatment regimens

The second part of the report focuses on the rationale for TBI therapy and the available drug regimens. It outlines the factors to consider in treatment selection for a child or adolescent with TBI. Principles of treatment include efficacy against progression to TB disease, safety and completion of the regimen.

The traditional six- to nine-month course of isoniazid (INH) monotherapy has poor real-world adherence given the prolonged length. Rifamycin-containing regimens (e.g., three months of INH and rifapentine, four months of rifampin alone or three months of INH and rifampin) are appealing given their shorter duration and safety and efficacy profiles comparable to INH monotherapy. Rifamycin-containing regimens are preferred for treatment of TBI.

Dr. Nolt is a lead author of the clinical report and a member of the Committee on Infectious Diseases.


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