title: Utility of an interferon-gamma release assay as a potential diagnostic aid for active pulmonary tuberculosis.
abstract: BACKGROUND
  Sensitivity, specificity, early confirmation and obtaining an optimal specimen are challenging problems in active tuberculosis (TB) diagnosis. Interferon-gamma release assay (IGRA) is a good indicator for latent TB but can it be useful as a diagnostic tool for active TB? This study was designed to address these challenges and assess the potential of IGRA as a diagnostic indicator of active pulmonary TB by comparing it with other MT diagnostic conventional methods and molecular methods.
  
  
  METHODS
  The study was conducted on 91 patients with suspicion of pulmonary active TB. QuantiFERON-TB-Gold In-Tube, a commercial IFN-gamma assay, was compared with Ziehl Neelsen (ZN) smear, Lowenstein Jensen's (LJ) egg-based culture, and real-time polymerase chain reaction. The final clinical diagnosis was the standard comparator of the study.
  
  
  RESULTS
  Active pulmonary TB was confirmed in 48/91 (52.7%) patients. Sensitivity, specificity, positive predicted value (PPV), and negative predicted value (NPV) were 72.9%, 100%, 100%, 76.78% for ZN smear, 77.1%, 97.67%, 97.36%, 79.24% for LJ culture, 89.9%, 67.4%, 75.4%, 85.3% for IGRA, and 66.6%, 95.3%, 94.1%, 71.9% for real-time PCR, respectively.
  
  
  CONCLUSIONS
  Albeit confounding in the case of latent TB infected patients presenting with non-TB pulmonary disease, IGRA was more sensitive than the other conventional and molecular methods, so it may improve diagnostic accuracy when used in combination with other standard methods. High NPV of IGRA for the diagnosis of active TB proposed an additional role of this test to exclude the infection with active TB.
authors.affiliation: Department of Biochemistry, Faculty of Pharmacy, Damascus University, Damascus, Syria. lynn_td@hotmail.com
authors.forename: Lynn
authors.initials: L
authors.lastname: Taki-Eddin
authors.forename: Fawza
authors.initials: F
authors.lastname: Monem
mesh_terms: D001431:Bacteriological Techniques; D003470:Culture Media; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D059425:Interferon-gamma Release Tests / Q000379:methods*; D055985:Latent Tuberculosis; D008853:Microscopy / Q000379:methods; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000276:immunology / Q000382:microbiology
chemical_list: D003470:Culture Media; D011933:Reagent Kits, Diagnostic; D007371:Interferon-gamma