[Usefulness of interferon-gamma-based diagnosis of Mycobacterium tuberculosis infection in childhood tuberculosis].

We studied the usefulness of interferon-gamma measurement reagent QuantiFERON-TB 2 G (QFT-2G), used to diagnose tubercle bacilli infections, as an indicator both for diagnosing primary tuberculosis (PTB) and for assessing therapeutic amorg pediatric Tuberculosis Outpatent cases effectiveness. Five cases showing typical PTB findings, such as cavitation, swollen lymph nodes, and nodular shadows at the pulmonary hilum, and diagnosed as tubercle bacillus infections, all showed positive reactions to QFT-2G, and in 3 asymptomatic cases without abnormalities detected in diagnostic imaging but QFT-2G-positive, one developed tuberculosis (TB) later. Among 12 patients who gave negative reactions to QFT-2G at their first visit and during observation from 6 months to 1 year, no TB occurrences was seen. Patients who were vaccinated for BCG and were tuberculin-positive showed negative reactions to QFT-2G, confirming that QFT-2G is not affected by BCG. One case of nontuberculous acid-fast bacilli in which Mycobacterium avium was detected was QFT-2G-negative. In 1 case, QFT-2G decreased as the patient's conditiorl improved. Without being influenced by BCG vaccination, QFT-2G demonstrated its usefulness in primary TB cases both for diagnosis and for assessing treatment effectiveness. Our results strougly suggested that QFT-2G is a potentially powerful tool with wide applications in diagnosis and assessment of treatment effectiveness in primary TB, even when bacterial elimination is low and diagnosis is difficult.