Interferon-gamma release assays in patients with Mycobacterium kansasii pulmonary infection: A retrospective survey

Summary Objectives Interferon-gamma release assays (IGRAs) can be positive in patients infected with Mycobacterium kansasii (M. kansasii) , which carries some of Mycobacterium tuberculosis specific antigens adopted for IGRAs. Our aim is to evaluate positive rate and factors associated with positive IGRAs in patients with M. kansasii pulmonary infection. Methods We retrospectively investigated 105  M. kansasii cases in which IGRAs were performed before or ≦14 days after treatment initiation. Clinical characteristics including a history of tuberculosis, radiographic features and laboratory data were collected from medical records. Results Positive rate of each IGRA was 25.9% (15/58) in QuantiFERON TB-Gold (QFT-G), 31.8% (7/22) in QuantiFERON-TB Gold In Tube (QFT-GIT), and 33.3% (7/21) in T-SPOT. TB (T-SPOT). After excluding cases having a history of tuberculosis, positive rate of each IGRA decreased to 19% (8/42) in QFT-G, 20% (3/15) in QFT-GIT, and 18.8% (3/16) in T-SPOT. The multivariate analysis revealed that only previous tuberculosis was significantly associated with positive IGRAs (odds ratio, 4.758; 95% confidence interval, 1.73–13.05; p = 0.002). Conclusions Positive rates of IGRAs were low in patients with M. kansasii , especially in those without previous tuberculosis. M. kansasii pulmonary infection alone might induce less interferon-gamma production with the antigens.