Carcinoembryonic antigen levels in benign and malignant pleural effusions.

One hundred ninety-one unselected fluid specimens submitted routinely for cytologic examination were assayed to determine whether the measurement of carcinoembryonic antigen (CEA) levels in pleural effusions is useful in detecting malignancy. The mean +/- SD CEA level of 103 benign effusions was 4.1 +/- 2.9 ng/ml. Only one benign effusion had a level greater than 12 ng/ml (18 ng/ml). Benign inflammatory effusions (pneumonia, empyema) had a higher mean CEA activity (6.2 +/- 3.4) than effusions caused by congestive heart failure (2.9 +/- 1.5) (p less than 0.001). Twenty-four (34%) of 70 malignant effusions had a CEA level greater than 12 ng/ml, and 28 (40%) were "positive" by cytologic study. Thirty-eight (54%) were detected by one or both methods. Ten malignant effusions were positive by CEA (greater than 12 ng/ml) alone. These data suggest that the determination of CEA activity levels, when used in conjunction with other clinical findings, may be useful in detecting malignant pleural effusions.