The role of interferon-gamma release assays in the diagnosis of active tuberculosis
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Daniele Bendayan1, Atara Hendler, Klementy Litman
1Pulmonary and Tuberculosis Department, Shmuel Harofe Hospital, Beer Yaakov, Israel. daniellbd@hotmail.com
Background:
Interferon-gamma release tests are appealing alternatives to the tuberculin skin test (TST) for latent tuberculosis infection.
Objectives:
To determine the yield of the Quantiferon TB Gold test (QFT-G) in the diagnosis of active tuberculosis disease, with a focus on elderly patients, human immunodeficiency virus (HIV) co-infection, and extra-pulmonary tuberculosis (EPTB).
Methods:
The QFT-G test was performed in 98 patients suspected of having active tuberculosis. The results were evaluated for each subgroup of patients and compared to the results of the TST.
Results:
Active tuberculosis was diagnosed in 92 of the 98 patients. Sixteen (17.3%) were elderly patients (over age 70), 15 (16%) were co-infected with HIV, and 14 (15%) had EPTB. QFT-G was positive in 49 patients (53%) and indeterminate in 4. The results were not significantly affected by HIV coinfection (P = 0.17), old age (P = 0.4), orthe presence of EPTB (P = 0.4). There was a good correlation between the TST and the QFT-G test (P < 0.001). In EPTB and in the elderly, the QFT-G test appears to be better than the TST.
Conclusions:
The QFT-G test is suboptimal in its ability to detect active tuberculosis and should not be used to exclude it.
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