Version July 2025
IGRA: interferon-gamma release assay; TB: tuberculosis; TBI: tuberculosis infection; TST: tuberculin skin test.
* For indications for TBI testing, refer to the UpToDate topic on approach to diagnosis of TBI. Only those who would benefit from treatment of TBI should undergo testing, so a decision to test presupposes a decision to treat if the test is positive.
¶ If the first test is negative, close contacts (defined as individuals who share an enclosed space with a patient with untreated respiratory TB disease for ≥4 hours per week) should undergo a second test eight weeks later. Many TB programs test casual contacts only once at eight weeks after exposure.
Δ In general, either IGRA or TST may be used; IGRA is preferable if available, particularly for patients who are unlikely to return to have the TST read and for patients with a history of Bacille Calmette-Guerin (BCG) vaccination administered after 12 months of age.
◊ Interpretation of TST result depends on the nature of the underlying condition (refer to the UpToDate topic on interpretation of TST).
§ IGRA results only slightly above the cutoff value for the positive test recommended by the manufacturer, are more likely to revert to negative spontaneously, and are associated with lower risk of progression to TB disease. For this reason, we review the numeric results carefully. For patients with results that are less than double the cutoff value for a positive test), we consider of repeating the test, with individualized patient management.
