251 Interferon-Gamma Release Assay—Useful Tool for the Diagnosis of Pleural Tuberculosis

Abstract

BackgroundPleural tuberculosis represents a big problem to diagnose despite of many diagnostic tools. CD4+T-lymphocytes play an imprortant role in immune response against Mycobacterium tuberculosis. They are accumulated in pleural space affected with Mycobacterium tuberculosis and release an inflammatory cytokines (interferon-γ, interleukin-2). These cytokines interact with macrophages to stimulate effective antimycobacterial actions. The pleural fluid lymphocytes and interferon-γ level are elevated in many cases such as viral infections, malignancy or tuberculosis. We decided to evaluate a benefit of utilization of antigen specific Interferon-gamma release assay (IGRA) in pleural effusion (PE) to the diagnostics of pleural tuberculosis.MethodsWe present results of 29 patients with lymphocytic PE of unknown cause. The total leukocytes count, lymfocyte subsets by flow cytometry with monoclonal antibodies directed against the T-lymphocyte antigens (CD3, CD4, CD8) and HLA DR antigen as a marker of T-lymphocyte activation were determined in PE. IGRA test was used to determine a level of specific interferon-gamma in PE and in whole blood too. Furthermore we analysed results of tuberculin skin test and Mycobacterium tuberculosis cultivation in the sputum and in PE.ResultsOf the 29 lymphocytic PE was IGRA test positive in 3 cases (10,3%). These patients had the pleural effusion with activated CD4 + T-lymphocytes predominance, elevated CD4/CD8 ratio. Mycobacterium tuberculosis cultivation was negative in both sputum and pleural fluid except 1 patient with positive sputum culture. The tuberculin skin test was higher than 15 mm of all 3 patients. The clinical diagnosis of active pleural tuberculosis was confirmed in these patients. AntiTB treatment was successful of all them. Lymphocytic PE with negative IGRA test was in 26 patients (89,7%): malignancy in 7, heart failure effusion in 3, parapneumonic effusion in 8 and other pathological causes was in 8 patients.ConclusionsOur results acknowledge that IGRA test applied to pleural fluid is very helpful to the diagnostics of pleural tuberculosis because the pleural fluid interferon-γ level is measured after stimulation of T-lymphocytes by tuberculous specific antigens. We conclude that another important benefit of interferon-γ release assays is the differential diagnostics of CD4+T-lymphocytic pleural effusions.