title: Diagnostic value of ex vivo pleural fluid interferon-gamma versus adapted whole-blood quantiferon-TB gold in tube assays in tuberculous pleural effusion.
abstract: BACKGROUND
  Noninvasive diagnosis of pleural tuberculosis (TB) remains a challenge due to the paucibacillary nature of the disease. As Mycobacterium tuberculosis (MTB)-specific T cells are recruited into pleural space in TB effusion; their indirect detection may provide useful clinical information.
  
  
  OBJECTIVE
  Evaluation of pleural fluid interferon (INF)-γ levels vs Quantiferon-TB Gold In tube assay (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 presented at Assiut University Hospital, Egypt, were recruited. Blood and pleural fluid were collected at presentation for INF-γ assays. Ex vivo pleural fluid INF-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 TB in 20 (53%), malignancy in 10 (26%), and effusion due to other causes in eight patients (21%). Ex vivo pleural fluid INF-γ levels accurately identified TB in all patients and were superior to the QFT-IT assays using blood or pleural fluid (70 and 78% sensitivity, with 60 and 83% specificity, respectively). 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 assay in blood assay, 0.82 IU/ml for the cultured pleural fluid assay, and 0.94 for isolated pleural cells assay.
  
  
  CONCLUSIONS
  The ex vivo pleural fluid INF-γ level is an accurate marker for the diagnosis of pleural TB. QFT- IT assay in peripheral blood or its adapted versions of the assay using pleural fluid and/or washed pleural fluid cells had no diagnostic advantage over pleural fluid INF-γ in the diagnosis of pleural TB.
authors.affiliation: Department of Clinical Pathology, Assiut University Hospital, Egypt.
authors.forename: Eman N
authors.initials: EN
authors.lastname: Eldin
authors.forename: Asmaa
authors.initials: A
authors.lastname: Omar
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Khairy
authors.forename: Adel H M
authors.initials: AH
authors.lastname: Mekawy
authors.forename: Maha K
authors.initials: MK
authors.lastname: Ghanem