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The introduction of interferon (IFN)-based whole-blood tests for latent TB has sparked debate about how best to detect this condition. The classic tuberculin skin test (TST) is inexpensive but nonspecific; the newer IFN-γ assays, although costly, appear to be more specific. Some patients with positive TST results have an IFN-γ assay performed soon thereafter. In a cross-sectional study conducted in South Korea, researchers investigated whether recent skin-test exposure to tuberculin might alter the immunologic reaction on which IFN-γ assays are based. Participants were healthcare workers who were determined by chest x-ray not to have active pulmonary TB or previous TB scarring.
Blood was obtained for a baseline IFN-γ assay, and then the TST …