Diagnostic value of carcinoembryonic antigen (CEA) assay in pleural effusions.

Carcinoembryonic antigen (CEA) levels were evaluated by a direct radioimmunoassay in the effusion fluids and plasma samples from 107 patients with pleural effusions of unknown etiology. CEA levels higher than 20 ng/ml were detected in 55% of pleural effusions from patients with malignant disease: 40% of the patients in this group had values of plasmatic CEA lower than 20 ng/ml. With the only exception of 4 patients with empyema, CEA levels were uniformly lower than 20 ng/ml in the effusion fluid of patients with benign disease. Moreover, CEA levels higher than 20 ng/ml were observed in 81.2% of pleural effusions and 31.2% of plasma samples from patients with cytology positive for malignancy, whereas increased CEA levels were observed in 37.5% of effusion fluids and 33.3% of plasma samples from patients with malignant disease but negative cytology in the pleural effusion. CEA assay in the effusion fluid represents a useful tool of high specificity and good sensitivity to discriminate between benign and malignant etiology of pleural effusions.