Immunoradiometric assay of CA 125 in effusions. Comparison with carcinoembryonic antigen

The levels of CA 125 antigen were measured in 167 effusions from 150 patients using radioimmunoassay, and the results compared with the levels of carcinoembryonic antigen (CEA) in the fluids. This study was carried out to test a hypothesis that measuring the combined levels of selected tumor associated antigens in effusions could predict the primary source of malignancy. The results indicate that an elevated fluid CA 125 level (greater than 14,000 U/ml-68,000 U/ml) and a negative fluid CEA level (less than 5 ng/ml) is suggestive of serous and endometrioid carcinoma of ovary, and adenocarcinoma of the endometrium and fallopian tube. Alternatively, an elevated fluid CEA level (14 ng/ml-600 ng/ml) and a negative CA 125 level (20-5000 U/ml) is seen in metastatic carcinomas of breast, lung, gastrointestinal tract, and mucinous cystadenocarcinoma. Lymphomas, melanomas, and benign effusions are negative for both antigens. The combined use of CEA and CA 125 antigen in fluids is useful in the differential diagnosis of adenocarcinoma of unknown primary.