Clinical evaluation of the QuantiFERON-TB Gold test in patients with non-tuberculous mycobacterial disease.

OBJECTIVE: To evaluate the clinical usefulness of the QuantiFERON TB-2G (QFT-2G) test in patients with non-tuberculous mycobacterial (NTM) disease without a previous history of tuberculosis (TB).

METHODS: The study consisted of 214 patients with NTM disease who satisfied the diagnostic guidelines of the American Thoracic Society.

RESULTS: The causative microorganism was Mycobacterium avium in 83 patients, M. intracellulare in 80, M. kansasii in 33, M. marinum in 12, M. szulgai in 3, M. abscessus in 2 and M. chelonei in 1. The positive response rate of QFT-2G test result was 2% in 163 patients with M. avium-intracellulare complex (MAIC) disease, 52% in 33 with M. kansasii disease, 58% in 12 with M. marinum disease, 33% in 3 with M. szulgai disease, 0% in two with M. abscessus disease and 0% in one with M. chelonei disease. The positivity of the QFT-2G test was 52% in patients with NTM disease, thought to be because NTM possesses common M. tuberculosis-specific antigens.

CONCLUSIONS: Although QFT-2G may be a useful diagnostic method to differentiate TB from MAIC disease, there are several problems to be resolved before it can be used as a diagnostic method for NTM disease (M. kansasii disease), including the determination of the positive cut-off level for QFT-2G test.