Interferon gamma levels in pleural fluid for the diagnosis of tuberculosis.

PURPOSE: To assess the utility of interferon gamma levels, including identification of the best cutoff for the diagnosis of tuberculosis. METHODS: We prospectively studied consecutive patients in a tertiary care, university-affiliated hospital who had pleural effusions. Interferon gamma levels were measured blindly by radioimmunoassay. The diagnosis of tuberculosis was established using prespecified standard criteria. RESULTS: Of the 595 patients with pleural effusions, 82 patients (14%) had tuberculosis. The area under the receiver operating characteristic (ROC) curve for elevated interferon gamma levels in the diagnosis of tuberculosis was 0.99 (95% confidence interval [CI]: 0.97 to 1.00). A cutoff of 3.7 IU/mL yielded a sensitivity of 0.98 (95% CI: 0.91 to 1.00) and a specificity of 0.98 (95% CI: 0.96 to 0.99). The areas under the ROC curves, and the test's sensitivity and specificity, were similar among patients of different ages and by percentage of lymphocytes in the pleural fluid. In 5 of the 28 patients with hematologic malignancies, interferon gamma levels were slightly above the cutoff; no patient with vasculitis or granulomatous diseases had levels higher than 3.7 IU/mL. The 14 immunocompromised patients and the 3 transplantation patients with tuberculosis had interferon gamma levels greater than the cutoff. CONCLUSION: Elevated pleural interferon gamma levels (>3.7 IU/mL) are very valuable in diagnosing pleural tuberculosis. Patients with pleural effusion due to hematologic neoplasms occasionally have levels slightly above the cutoff.

Diagnostic value of CA 549 in pleural fluid. Comparison with CEA, CA 15.3 and CA 72.4.

Several tumor markers have been evaluated in pleural fluid, but their clinical role has not been firmly established. The aim of this study is to determine the diagnostic value of carbohydrate antigen 549 (CA 549) levels in pleural fluid, and to compare it with another previously studied tumor markers: carcinoembryonic antigen (CEA), CA 15.3 and CA 72.4. We prospectively studied 252 patients with pleural effusion: 101 malignant (20 mesothelioma) and 151 of several benign diseases. The levels of the tumor markers were measured by immunoradiometric assays (RIA). CA 549 in pleural fluid has an acceptable sensitivity (0.49), with high specificity (0.99). The best combination of tumor markers for differentiating malignant from benign effusions was CA 549+CEA+CA 15.3, with a sensitivity of 0.65, specificity of 0.99 and accuracy of 0.85. The addition of any one tumor marker assay consistently improved the diagnostic value of cytology. In our study, none of the tumor markers was organ-specific. When mesothelioma and hematological malignancy were ruled-out, the combination of CA 549+CEA+CA 15.3, improved the results up to a sensitivity of 0.77, specificity of 1 and accuracy of 0.92. In conclusion, CA 549 assay has an acceptable sensitivity with high specificity. The best combination of tumor markers in this series with a high relative frequency of mesothelioma and low frequency of breast carcinoma was CA 549+CEA+CA 15.3. Individual tumor markers or their combination increased the sensitivity of pleural cytology.