The diagnostic efficiency of QuantiFERONTB®-Gold test in the diagnosis of tuberculous pleurisy

Background: Diagnosis of tuberculous pleurisy is difficult and better diagnostic tools are needed. Interferon gamma release assays (IGRAs) are in vitro immunologic diagnostic tests used to identify Mycobacterium TB infections. They cannot differentiate between latent and active infections. As IGRA tests have recently been approved for the differential diagnosis of active TB, the diagnostic accuracy of the latest generation of IGRA were assessed to detect tuberculous pleurisy in this study. Methods: The QuantiFERONTB®-Gold (QFT-G) test was used in pleural fluid from 100 immunocompetent patients (23 patients for the tuberculous group and 77 patients for the non-tuberculous group). Clinical data were recorded. Adenosine deaminase activity (ADA) analysis and TB culture were performed on pleural fluid. Results: The QFT-G in pleural fluid was positive in 10 (43.5%) patients and indeterminate in 13(56.5%) patients in the tuberculous pleurisy group. There was not a single patient with a negative test result in the tuberculous pleurisy group. The ADA levels were detected as 46.2 ± 12.6 in patients with tuberculous pleurisy and18.6 ± 39.8 in patients with non-tuberculous pleurisy. The sensitivity, specificity, positive predictive value and negative predictive value of QFT-G in pleural fluid for tuberculous pleurisy were 43.5%, 54.5%, 30.3% and 100%; and of ADA in pleural fluid (>40IU/ml) for tuberculous pleurisy the results were 82.6%, 96.1%, 90.5% and 92.5% respectively. Conclusion: While the value of the QFT-G test in exclusion of tuberculous pleurisy was found to be higher in this study, its other diagnostic efficiency values were detected to be low. It is recommended that a new cut-off value be established while diagnosing active TB in prospective clinical studies and that it is also essential to do the same for the studies in various regions with high and low prevalence of TB