The century-old tuberculin skin test (TST) was until recently the only means of diagnosing
latent tuberculosis infection (LTBI). Recent advances in mycobacterial genomics and human
cellular immunology have resulted in two new blood tests that detect tuberculosis infection
by measuring in vitro T-cell interferon (IFN)-γ release in response to two unique antigens
that are highly specific for Mycobacterium tuberculosis but absent from bacille Calmette-
Guérin (BCG) vaccine and most nontuberculous mycobacteria. One assay, the enzyme …