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KMID : 1100820160060010008
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Laboratory Medicine Online
2016 Volume.6 No. 1 p.8 ~ p.11
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Clinical Applications of Interferon-gamma Release Assays
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Woo Kwang-Sook
Kim Kyeong-Hee
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Abstract
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Mycobacterium tuberculosis infection remains an important problem in Korea and globally. Interferon-gamma release assays (IGRAs) are blood-based tests that measure the amount of interferon-gamma released by T lymphocytes after stimulation by antigens specific for M. tuberculosis. IGRAs are not recommended for diagnosis of active pulmonary tuberculosis because they cannot distinguish between latent tuberculosis infection (LTBI) and the active disease. For extrapulmonary tuberculosis, IGRAs are considered adjuvant diagnostic tools. The diagnostic performance of IGRAs differs according to infection site. The sensitivity of IGRAs in children is suboptimal in low- and middle-income countries. In Korea, for children who have received a M. bovis bacille Calmette-Guerin (BCG) vaccine after 1 yr of age or have been inoculated with the BCG vaccine twice or more, IGRA is recommended instead of the tuberculin skin test (TST). Diagnosis and treatment of LTBI before the initiation of anti-tumor necrosis factor (TNF) agents are recommended in patients with immune-mediated inflammatory diseases because anti-TNF therapy is associated with an increased risk of developing tuberculosis. A strategy using both TST and IGRA is used for immunocompromised adults in Korea; positive results obtained by either test confirm a diagnosis of LTBI. Negative results of only TST are not considered conclusively negative for LTBI. In addition to interferon-gamma, a biomarker to discriminate between active and latent tuberculosis is required, and IP-10 and IL-2 are currently being investigated in this regard. The use of IGRA would improve the diagnosis of extrapulmonary tuberculosis and LTBI.
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KEYWORD
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Interferon-gamma release assays, Latent tuberculosis, Sensitivity, Specificity
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