Persistently Retained Interferon-Gamma Responsiveness in Individuals with a History of Pulmonary Tuberculosis

Persistently Retained Interferon-Gamma Responsiveness in Individuals with a History of Pulmonary Tuberculosis

KWANG WON SEO,¹ JONG-JOON AHN,¹ SEUNG WON RA,¹ WOON-JUNG KWON² and YANGJIN JEGAL¹

¹Department of Internal Medicine, Ulsan University Hospital, University of Ulsan, College of Medicine, Ulsan, Korea
²Department of Diagnostic Radiology, Ulsan University Hospital, University of Ulsan, College of Medicine, Ulsan, Korea

The interferon gamma (IFN-γ) release assays (IGRAs) are the best method of detecting Mycobacterium tuberculosis infection. However, reports on IGRAs results obtained during and right after the treatment of tuberculosis (TB) have presented differing results. Some studies have shown declining responses, whereas other reports described persistent, fluctuating, or increasing responses. We postulated that the IGRA-positivity will decrease or revert long time after treatment of TB, and thus, evaluated the response of IGRA in subjects with a history of pulmonary TB. Seventy subjects (M:F = 51:19; age = 53.2 ± 11.8 years) underwent tuberculin skin tests (TSTs) and IGRA. The interval of time elapsed after the completion of anti-TB treatment was < 10 years for 16 subjects, 10-20 years for 13 subjects, 20-30 years for 16 subjects, and ≥ 30 years for 25 subjects. The TST was positive in 49 subjects (74%) and negative in 17 subjects (26%). The IGRA was positive in 52 subjects (74%) and negative in 18 subjects (26%). The IFN-γ level and the size of induration showed good correlation (r = 0.525, P < 0.001). However, the correlation between time elapsed after the completion of anti-TB treatment and the size of induration or that between time and the IFN-γ level was not significant. The TST and IGRA were positive in 72.7% and 68.0% of subjects ge; 30 years after the treatment of pulmonary TB. In conclusion, majority of subjects with a history of pulmonary TB are IGRA-positive, even a few decades after the completion of anti-TB treatment.

keywords —— history of pulmonary tuberculosis; interferon-gamma release assays; latent tuberculosis; reversion; tuberculin skin test

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Tohoku J. Exp. Med., 2014, 233, 123-128

Correspondence: Yangjin Jegal, M.D., Department of Internal Medicine, Ulsan University Hospital, 877 Bangeojinsunwhan-doro, Dong-gu, Ulsan 682-714, Korea.

e-mail: yjjegal@gmail.com