ied from 1 to 500 pi. Plasma samples were obtained from EDTA-treated whole blood. Quantitation of Serum CEA by Radioimmunoassay. CEA levels in sera were determined by Todd-Egan double anti body radioimmunoassay (3) as modified by Laurence et a!. (7), using goat anti-CEA serum (Peanuts 12). CEA levels in plasma were determined either by indirect or direct Hansen Z-gel radioimmunoassay (6), as in...