PANCE Pulmonology Practice Test

Which statement about TB IGRA interpretation is true?

The IGRA can differentiate active TB from latent TB. IGRA results always require follow-up interpretation. IGRA results have false positives with BCG vaccination. IGRA interpretation cannot differentiate active from latent TB.

Correct Answer:

IGRA interpretation cannot differentiate active from latent TB.

Explanation:

TB IGRA tests measure T-cell release of interferon-gamma in response to TB-specific antigens, which indicates infection with Mycobacterium tuberculosis but does not reveal whether the infection is active or latent. That limitation is why this statement is true: the test cannot differentiate active TB from latent TB based on IGRA results alone. IGRA's specificity is higher in BCG-vaccinated individuals because the antigens used are not present in BCG strains, so prior vaccination does not cause a false-positive IGRA. However, you still determine active disease through clinical evaluation, chest imaging, and microbiologic confirmation, since IGRA cannot distinguish disease activity.

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