Lab Med Online.  2020 Jan;10(1):58-65. 10.3343/lmo.2020.10.1.58.

Different Quantitative Interferon-γ Response in Active Tuberculosis of Various Primary Infection Sites

  • 1Department of Internal Medicine, Dong-A University College of Medicine, Busan, Korea.
  • 2Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Korea.


The quantitative interferon (IFN)-γ response in the IFN-γ release assay (IGRA) has been investigated to predict progression from Mycobacterium tuberculosis infection to active tuberculosis (TB). However, the significance of the quantitative IFN-γ response in active TB is rarely known. We assessed the association between IFN-γ response to nil, mitogen, and TB mycobacterial antigens, and the variations from serial IGRA testing in active TB of various primary infection sites.
In total, 102 active TB patients with serial QuantiFERON-TB Gold In-Tube (QFT-GIT) (Qiagen, Germany) were enrolled. The medical records of patients were reviewed for demographic information, infection sites, tuberculosis treatment, and the quantitative IFN-γ response to nil, mitogen, and TB antigen.
Patients included 20, 68, and 14 cases of pulmonary TB, extrapulmonary TB, and multiple TB infection, respectively. The quantitative IFN-γ responses to TB antigens differed significantly according to the infection sites (P=0.0001). The median IFN-γ response was the highest in lymph node infection (10.0 IU/mL) and the lowest in central nervous system (CNS) infection (0.02 IU/mL). Of the total, 86.3% showed concordant results in serial testing. Both 50% of the patients with persistent negative results and 62.5% of patients with CNS TB had an insufficient IFN-γ response to mitogen.
Different IFN-γ responses to TB antigens may indicate variable host immune responses among infection sites in active TB disease. Because a few active TB patients fail to produce an adequate IFN-γ response, a study of cellular mechanisms is needed in such unresponsive patients.


Mycobacterium tuberculosis infection; Serial interferon-γ release assay; QuantiFERON-TB Gold In-Tube; Interferon-γ; Quantitative; Mitogen; Conversion; Reversion
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