Radioimmunoassay of carcinoembryonic antigen in serum of normal subjects and patients with colonic carcinoma

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Abstract
Sera from 14 normal subjects and 43 patients with colonic carcinoma were evaluated for the presence of carcinoembryonic antigen (CEA). Inhibiting material which behaved in the assay in a similar manner to CEA was found in normal serum at concentrations below 2·8 ng/ml. Its nature has not so far been established. Thirty-eight of the 43 patients with colonic carcinoma showed levels of serum CEA in excess of 2·8 ng/ml. The concentration of CEA in serum was correlated with the extent of the disease as classified by a staging procedure similar to that of Dukes (1932). Examination of a small number of specimens of colonic carcinoma and normal colonic mucosa suggested that the concentration of CEA in different adenocarcinomata may vary, and that traces of cross-reacting material may be found in some normal mucosae.