Diagnostic significance of gamma-interferon in tuberculous pleurisy

We studied ADA and gamma interferon (gamma-IFN) levels in pleural fluid of 45 cases presenting with pleural effusion to the Ankara University School of Medicine Chest Diseases Hospital between September 2001 and September 2002. Fifteen patients had TB pleurisy, 20 patients had malignant pleurisy and 10 patients had transudative pleural effusion. The cut-off value for pleural fluid gamma-IFN levels were 12 pg/mL. According to this, all patients with transudative effusions, 19 of 10 patients with malignant effusions and 2 of 15 patients with tuberculous (TB) effusions had pleural fluid gamma-IFN levels under the cut-off value. In exudative effusions, sensitivity and specificity of gamma-IFN were 87% and 95% respectively. The sensitivity of pleural fluid ADA levels was 86% and specificity of pleural fluid ADA levels was 100%. Pleural fluid ADA levels in TB effusions were significantly higher than the non-TB effusions. Also there were no statistically significant differences between pleural fluid ADA and g-IFN levels according to sensitivity and specificity. As a result, we have shown that gamma-IFN is a valuable test in diagnosis of TB pleurisy. We think that when it is used routinely, it will be a good alternative to the conventional invasive diagnostic tests.