Latent TB Infection: Other Diagnostic Considerations

Latent TB Infection: Guide for Diagnosis and Treatment

Diagnosis

Other Diagnostic Considerations

Chest Radiograph

Chest radiographs help differentiate between LTBI and pulmonary TB disease in individuals with positive tests for TB infection. The following guidelines are recommended:

• A chest radiograph should be ordered as part of a medical evaluation for a person who has a positive TST or IGRA result.
• A chest radiograph is also indicated in the absence of a positive test result for TB infection when a person is a close contact of an infectious TB patient and treatment for LTBI will be started (e.g., “window prophylaxis” in a young child or immunocompromised person).
• Children less than 5 years of age should have both posterior-anterior and lateral views; all others should have at least posterior-anterior views.
• Other views or additional studies should be done based on the health care provider’s judgment.
• Persons with nodular or fibrotic lesions consistent with old TB are high-priority candidates for treatment of LTBI after TB disease is excluded.
• Persons with fully calcified, discrete granulomas do not have an increased risk for progression to TB disease.

Sputum Examination for AFB Smear and Culture

Sputum examination is indicated for persons with positive test results for TB infection and either an abnormal chest radiograph or the presence of respiratory symptoms (even when the chest radiograph is normal).

Physical Examination and Medical History

Physical examination and medical history, which includes obtaining information about previous positive tests for TB infection, previous treatment for LTBI or TB disease, and a risk assessment for liver disease, are indicated for an individual with positive TB test results. Written documentation of a previously positive TST or IGRA result is required; a patient’s verbal history is not sufficient.