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Chest Infections |

Diagnostic Value of Quantitative Measurement of Pleural Fluid Interferon-Gamma (IFN - γ) Versus QuantiFERON-TB Gold in Tube Assays (QFT-IT) in Blood, Pleural Fluid, and Isolated Pleural Fluid Cells in Tuberculous Pleural Effusion

Maha Ghanem, MD; Eman Nasr Eldin, MD; Asmaa Omar, MD; Mahmoud Khairy, MD; Adel Mekawy, MD
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Chest Department - Assiut University Hospital, Assiut, Egypt


Chest. 2013;144(4_MeetingAbstracts):262A. doi:10.1378/chest.1703850
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Abstract

SESSION TITLE: Respiratory Infections Posters

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 30, 2013 at 01:30 PM - 02:30 PM

PURPOSE: In low-Middle Income Countries (LMIC) with limited resources, noninvasive diagnosis of plerural tuberculosis (TB) remains a challenge helped by the paucibacillary nature of the disease. As Mycobacterium tuberculosis-specific T cells are recruited into pleural space in TB effusion; their indirect detection may provide useful clinical information. Hence, this study aims to evaluate pleural fluid IFN - γ levels versus QFT-IT in blood and its adapted variants, using pleural fluid or isolated pleural fluid cells in the diagnosis of pleural TB.

METHODS: Thirty eight patients with pleural effusion of unknown etiology were recruited. Blood and pleural fluid were collected at presentation for IFN−γ assays. Ex vivo pleural fluid IFN - γ levels, QFT-IT in blood and its adapted variants were compared with final diagnosis as confirmed by other tools including blind and/or thoracoscopic pleural biopsy.

RESULTS: The final clinical diagnosis was tuberculosis in 20 (53%), malignancy in 10 (26%), and effusion due to other causes in 8 patients (21%). Ex vivo pleural fluid IFN - γ levels accurately identified TB in all patients with efficiency 100% and were superior to the QFT-IT assays using blood or pleural fluid (70 and 78% sensitivity, with 60 and 83% specificity, respectively). The isolated pleural cells from patients with TB effusions produced significantly more INF-γ than non TB. Culture of washed pleural fluid cells stimulated with MTB-specific antigens did not lead to increased INF-γ levels compared with non-stimulated washed pleural fluid cells. QFT-IT assay applied to isolated pleural fluid cells had 100% sensitivity and 72% specificity. The optimal cut-off obtained with ROC analysis was 0.73 for TB Gold in blood assay, 0.82 IU/ml for pleural fluid assay, and 0.94 for isolated pleural cells assay.

CONCLUSIONS: The ex vivo pleural fluid IFN− γ level is an accurate marker for the diagnosis of pleural TB. QFT-IT assay in peripheral blood or its adapted versions using pleural fluid and/ or washed pleural fluid cells had no diagnostic advantage over pleural fluid IFN− γ in the diagnosis of pleural TB.

CLINICAL IMPLICATIONS: In limited resources settings, the quantitative measurement of pleural fluid IFN− γ level in pleural fluid is an accurate marker for the diagnosis of pleural TB and is superior to the more expensive QFT-IT assays . QFT-IT assays performed with blood, pleural fluid or pleural fluid cells does not add diagnostic value.

DISCLOSURE: The following authors have nothing to disclose: Maha Ghanem, Eman Nasr Eldin, Asmaa Omar, Mahmoud Khairy, Adel Mekawy

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