Radioimmunoassay of plasma carcinoembryonic antigen (CEA): Consideration of the results of two methods

Summary The two methods used to analyze 384 plasma samples were the carcinoembryonic antigen test (CRT) performed at the Roche laboratories and the direct radioimmunoassay plasma carcinoembryonic antigen (DRPC) technique. The first test, which is quantitative, gave many false positives below the 5 ng/ml level (also when used in a larger series of 4,628 subjects), thus invalidating its use for detection of gastrointestinal neoplasms. The DRPC technique was positive in 62.3 % of 101 cases of gastrointestinal adenocarcinoma and gave very few false positives.