Abstract: Objective: To investigate the application value of TB.IGRA assay in the diagnosis and differential diagnosis of Mycobacterium marinum infection. Methods: The data of suspected patients with M.marinum infection in out-patient treatment of our hospital were analyzed retrospectively. Exclusion of tuberculosis, the patients were divided into M.marinum infection group and control group (fungal and other bacterial infections) according to the qPCR result. TB.IGRA was used to detect tuberculosis infection-specific T cells of patients' peripheral blood. The sensitivity, specificity, predictive value and likelihood ratio between TB.IGRA and acid-fast staining in the diagnosis of M.marinum infection were compared and analyzed. We further discussed the sensitivity, specificity of TB.IGRA and γ- Interferon level of patients with M.marinum infection in different age groups. Results: A total of 87 patients with M.marinum infection and 25 controls were enrolled. The sensitivity and specificity of TB.IGRA assay were 73.56% and 64.0%, respectively. The positive and negative predictive value and likelihood ratio were 87.7%, 41.0%, 2.04 and 0.41, respectively. The sensitivity of young group, middle-aged group and old group were 70.0%, 73.5% and 74.4%, respectively. The specificity was highest in the middle-aged group (88.9%) and lowest in the elderly group (46.2%).  Conclusion: TB.IGRA has important application value in the diagnosis and differential diagnosis of M.marinum infection.

Key words: TB.IGRA&T-SPOT.TB, Mycobacterium marinum infection, nontuberculous mycobacteria