The value of pleural fluid carcinoembryonic antigen estimation in the diagnosis of malignant tumours of the pleural cavity.

Measurement of pleural fluid and blood carcinoembryonic antigen (CEA) concentrations as well as estimations of pleural fluid protein, lactic acid dehydrogenase and sugar levels were carried out in 45 patients with pleural effusions in order to determine the value of these biochemical parameters in the diagnosis of malignant tumours involving the pleural space. The study population included individuals with epithelial and non-epithelial malignant tumours involving the pleural cavity as well as patients with inflammatory effusions and patients with transudates due to cardiac, renal or hepatic disease. Pleural fluid CEA content was the single most useful measurement in distinguishing epithelial malignant tumours from other causes of pleural effusion. In addition, the pleural fluid CEA/blood CEA ratio was greater than 1 in most patients with epithelial cancer of the pleural space, suggesting that local production of CEA is responsible for elevated values in the pleural fluid.