Detection of carcinoembryonic antigen in the serum using a radioimmunoassay in patients with tumours of the alimentary tract: Clinical relevance of the test as judged from retrospective and prospective studies relating to the course of the disease - refinement of techniques pertinent to the assay

An improved double-antibody radioimmunoassay is described that was designed to detect CEA in the serum. The kinetic behaviour and binding of 125I-CEA and antiserum were found to be determined by such factors as time, temperature and incubation conditions and procedures based on sequential saturation proved more sensitive as compared to other methods. Radioiodination was achieved using the chloramine T technique. It was concluded that normal CEA values could not be interpreted so as to exclude the presence of a tumour, while values up to 10 ng/ml were also measured in non-malignant diseases. The CEA values were consistent with the stage of the tumour. In cases where increased CEA levels were determined before surgery, these returned to normal within a few weeks, if a cure had been achieved. No link could be established between the extent to which the baseline value was increased and the time elapsing before it was reversed to normal. (TRV)