Evaluation of a new monoclonal radioimmunoassay system for carcinoembryonic antigen

A newly established monoclonal radioimmunoassay system (kit II) for carcinoembryonic antigen (CEA) was evaluated in comparison to a conventional polyclonal system (kit I). Among 619 unselected serum samples, approximately 15% were CEA positive with kit I, whereas 27% were positive with kit II; consequently, approximately 12% showed dissociated CEA values to be positive only with kit II. More than 75% of patients with the dissociated values were found to have a malignant disease. Positive rates in normal individuals (266 samples) were less than 5% with both the kit I and kit II and, in those with benign disease were 11.9% with kit II, except for liver cirrhosis in which a quite high positive rate (58%) was obtained. In contrast, a definitely increased positive rate in malignant disease (381 samples) was obtained with kit II (61.4%) in comparison to that with kit I (42.3%). The assessment of technical qualities, such as reproducibility, recovery and dilution tests, demonstrated the excellent performance of kit II.