Carcinoembryonic antigen assay of ascites and detection of malignancy.

Levels of carcinoembryonic antigen (CEA) activity were measured in 105 unselected samples of ascitic fluid submitted for routine cytologic analysis to ascertain whether this assay was useful in the detection of malignancy. The highest CEA level found in the 70 specimens of "benign" ascites was 10 ng/ml. Using values greater than 10 ng/ml as indicating a cancerous effusion, CEA assay successfully detected 14 of the 29 malignant ascites studied. Cytology, on the other hand, detected only 12 of these fluids. Combining the two methods increased the yield to 20. The CEA assay alone thus detected more than one fourth of these malignant fluids. The assay was particularly useful in detecting malignant transudates, nearly half of which had elevated CEA levels despite negative cytologic findings. The CEA assay of ascites thus showed promise as an adjunct to cytology in the detection of malignant ascites when used as part of a complete clinical and laboratory assessment.