Whole blood interferon-γ assay for tuberculosis in children in Japan

Whole blood interferon-gamma assay QuantiFERON-TB2G (QFT-2G), which is a new specific method for diagnosing tuberculosis (TB), has been developed and used in the clinical field. The aim of the present study was to assess the usefulness of QFT-2G as an indicator, both for diagnosing childhood TB and for assessing therapeutic effectiveness. The subjects were 61 children introduced to the TB outpatient department for the first time between June 2004 and March 2006. QFT-2G, the tuberculin test and chest computed tomography (CT) were performed for all patients. Ten patients having typical characteristics of primary tuberculosis (PTB) on chest CT, and diagnosed as having tubercle bacillus infections, all had positive reaction on QFT-2G. Of seven patients who had no abnormalities on diagnostic imaging but who reacted positively on QFT-2G, one developed TB later, and no TB was detected over the period of observation in 44 patients with negative QFT-2G at their first consultation. Moreover, four patients with non-tuberculous acid-fast bacilli in which Mycobacterium avium or Mycobacterium gordonae was detected had negative reaction on QFT-2G. In addition, all 10 patients with positive reactions on QFT-2G in whom the subsequent course of the disease was observed had decrease on QFT after treatment. QFT-2G is a powerful tool with a wide application both in diagnosis and in assessment of treatment effectiveness in PTB.