[Diagnostic value of the combined determination of carcinoembryonic antigen (CEA) in pleural effusion and serum with an enzyme immunoassay (EIA). Sensitivity, specificity and relation to tumor type].

Measurement of carcinoembryonal (CEA) levels in pleural fluid are suggested to improve the unsatisfactory sensitivity of pleural cytology in the differential diagnosis of malignant pleural effusions. We evaluated simultaneously determined pleural and serum CEA levels in 117 patients with pleural effusions of different aetiology (74 malignant, 30 inflammatory exudates and 13 transudates) by use of an enzyme immunoassay (EIA). Despite considerable scatter, pleural levels of CEA in malignant effusions were significantly higher (p less than 0.001) than the values in benign effusions. Using a cut off level of 5 ng/ml, 41% (= sensitivity) of malignant pleural effusions showed elevated concentrations of CEA. Only one out of 43 benign effusions showed a level of 5 ng/ml, which is equivalent to a specificity of 98%. However, malignant effusions due to small cell lung cancer, pleural mesothelioma and metastasising ovarian carcinoma never showed elevated levels of CEA. Highest pleural values of CEA were observed in cases of alveolar cell or adenocarcinoma of the lung or metastasising breast cancer. Although pleural and serum CEA levels correlated significantly (rs = 0.77), the evaluation of serum CEA levels alone yielded a lower sensitivity (36%) and specificity (93%) than pleural levels. 77% of cases with malignant pleural effusions showing elevated pleural CEA levels were characterized by an increased ratio Pleura/Serum greater than 1, particularly in effusions due to lung cancer. The CEA ratio was significantly higher (p less than 0.05) in patients with malignant than with benign effusions. EIA appears to be more specific by avoiding false positive results in benign effusions as compared with determination by conventional RIA. In conclusion, evaluation of pleural CEA levels in patients with malignant effusions by using an EIA because of its high specificity is a valuable adjunct to pleural cytology in improving the diagnosis of malignant effusions. However, a normal CEA level in either pleural effusion or in serum is of no clinical significance. Simultaneous measurement in pleural effusion and serum is of greater value.