Discordance between Two Interferon-Gamma Release Assays in the Diagnosis of Latent Tuberculosis Infection in Healthcare Workers
|Hiroshi Fujiwara1, Tomoyasu Nishimura4, Osamu Iketani1, Yaoko Takano1, Akiko Sakai3, Naomi Kondo3, Kazuko Ohtake3, Shuji Oguchi3, Nobuko Shimizu3, Ayako Shibata3, Masatoshi Wakui2, Mitsuru Murata2, Masaaki Mori4, Satoshi Iwata1 and Naoki Hasegawa1*|
|1Center for Infectious Diseases and Infection Control, Japan|
|2Department of Laboratory Medicine, Keio University School of Medicine, Tokyo, Japan|
|3Central Clinical Laboratory, Keio University Hospital, Tokyo, Japan|
|4Health Center, Keio University, Kanagawa, Japan|
|Corresponding Author :||Naoki Hasegawa
Center for Infectious Diseases and Infection Control
Keio University School of Medicine
35 Shinanomachi, Shinjuku-ku
Tokyo 160-8582, Japan
E-mail: [email protected]
|Received July 23, 2014; Accepted September 23, 2014; Published October 13, 2014|
|Citation: Fujiwara H, Nishimura T, Iketani O, Takano Y, Sakai A, et al. (2014) Discordance between Two Interferon-Gamma Release Assays in the Diagnosis of Latent Tuberculosis Infection in Healthcare Workers. J Infect Dis Ther 2:171. doi: 10.4172/2332-0877.1000171|
|Copyright: © 2014 Fujiwara H, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.|
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Background: Interferon-gamma release assays (IGRAs) more accurately diagnose Mycobacterium tuberculosis (Mtb) infection than the tuberculin skin test. To prevent outbreaks in medical facilities, early detection and treatment of Mtb infection (including latent tuberculosis infection (LTBI)) is important in healthcare workers. Therefore, the IGRAs have considerable utility for Mtb infection control in medical facilities. In Japan, two IGRAs are commercially available, QuantiFERON®-TBGold In-Tube assay (QFT-GIT) and T-SPOT®.TB (T-SPOT). However, it remains unclear if diagnostic yields of LTBI by both IGRAs are equivalent in healthcare workers.
Methods: We performed both QFT-GIT and T-SPOT simultaneously in healthcare workers with a high risk of LTBI (excluding active tuberculosis) between December 2012 and February 2013.
Results: Among 313 subjects (excluding 2 cases with indeterminate T-SPOT), 6 (1.9 %) and 12 (3.8 %) were QFT-GIT positive and T-SPOT positive, respectively. There was no significant concordance of results between the QFT-GIT and the T-SPOT (p=0.064 and Kappa=0.43, 95% confidence interval 0.082-0.78). Among 10 discordant cases between two IGRAs, 8 cases had IGRAs’ results near the cutoff values.
Conclusion: Without a diagnostic gold standard for LTBI, it is difficult for us to further assess which test is more accurate and more suitable for the diagnosis of LTBI. However, to diagnose LTBI of healthcare workers with IGRAs’ results near the cutoff values, we should consider clinical context, such as contact level, as well as the results of IGRAs.