Assessment of Interferon-Gamma Release Assay in Patients with Non-Tuberculous Mycobacteria Pulmonary Disease

Background Interferon-gamma release assay (T-SPOT.TB) has the theoretical possibility of discriminating TB from most non-tuberculous mycobacteria (NTM) infections, but there are limited reports on the use of T-SPOT.TB for diseases due to NTM in high TB burden country. The aim of the present study was to assess the utility of T-SPOT.TB in patients with NTM pulmonary disease. Methods Clinical parameters and laboratory characteristics of patients with NTM pulmonary disease between July 2011 and Jan 2017 were investigated retrospectively and comprehensively reviewed. Results A total of 127 patients with NTM pulmonary disease were retrospectively reviewed. Seven NTM species were isolated from 115 patients, and the most common species were M. intracellulare (48.7%, 56/115) and M. abscessus (34.8%, 40/115). NTM isolates were mainly prevalent in people aged 50 years or older (73.0%). The overall positive rate of T-SPOT.TB test was 29.6% (24/81). In patients infected with NTM sharing the RD1 region of Mycobacterium tuberculosis (M. TB), 50% (3/6) were positive in the T-SPOT.TB test, whereas 28.0% (21/75) was positive in the group with NTM not sharing the RD1 region of M. TB. No significant difference was detected in the positive rate of T-SPOT.TB between definite (28.3%, 15/53) and probable disease (32.1%, 9/28). Conclusions Our data indicated a relatively high positive rate of T-SPOT.TB test in patients infected with NTM not sharing the RD1 region of M. TB. Thus, T-SPOT.TB test displays a limited ability in differentiating TB infection from NTM disease in a high TB burden country.