Simultaneous enzyme immunoassay of carcinoembryonic antigen in pleural effusion and serum.

A carcinoembryonic antigen (CEA) enzyme immunoassay test was used to estimate its value in the differential diagnosis of malignant and non-malignant pleural effusions. Paired pleural fluid and serum CEA determinations were performed in 107 patients, 53 with malignant and 54 with non-malignant pleural disease. CEA values uniformly lower than a cut-off level of 5.0 ng/ml were found in the pleural fluid and the serum in the non-malignant group, whereas in the malignant group, values higher than the cut-off level were present in the pleural fluid in 37 (69.8%), and in the serum in 30 (56.6%) of the examined patients. All 30 patients with elevated serum CEA levels also had pleural fluid CEA above 5.0 ng/ml. The results of this study demonstrate that although pleural fluid CEA values below 5.0 ng/ml do not exclude malignancy, increased values strongly suggest that the fluid is of malignant origin. Pleural fluid CEA determination had a 13.2% higher sensitivity, compared with that of the serum, in detecting malignant pleural involvement, yet with no statistical significance.