LTBI: latent tuberculosis infection; TB: tuberculosis; IGRA: interferon-gamma release assay; TST: tuberculin skin test.
* For indications for LTBI testing, refer to the UpToDate topic on approach to diagnosis of LTBI. Only those who would benefit from treatment of LTBI 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 of patients with active pulmonary TB 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).