The Value of Carcinoembryonic Antigen in Differentiating Malignant from Benign Pleural Effusion

Objectives: Pleural effusion may result from both malignant and benign pulmonary conditions, and is very important in making the differential diagnosis. Some biomarkers in the pleural effusion may help the process. We conducted a study to evaluate the feasibility of using carcinoembryonic antigen (CEA), proportion of lymphocytes, and various biochemical parameters in pleural effusion to differentiate between benign and malignant diseases. Materials and Methods: Samples of pleural effusion were obtained from 79 patients, including 21 with malignancies, 16 with paramalignant conditions, 19 with tuberculosis, and 23 with other benign diseases. CEA was measured using chemiluminescence immunoassay, and complete and differential cell counts were conducted by microscopic examination with Liu’s stain. Biochemical parameters were measured with an autoanalyzer. In addition to the comparison of the benign and malignant groups, we also compared these parameters between patients with tuberculosis and those with malignancy, as both have exudative effusion with lymphocyte predominance. Results: The CEA level was higher in patients with malignant effusion (76.3+121.4 ng/ml vs. 1.9+2.1 ng/ml, p ＜ 0.001 with the Mann-Whitney U test) than in those with benign effusion. With a cut-off level of 10 ng/ml, the sensitivity and specificity of CEA for diagnosing malignancy were 0.65 and 0.98, respectively. Together with cytology, the sensitivity could be raised to 0.73. Conclusion: The CEA assay of pleural effusion had an acceptable sensitivity and a high specificity in differentiating malignant from benign effusion.