Evaluation of a direct radioimmunoassay for carcinoembryonic antigen

1. A radioimmunoassay for CEA using commercially available reagents (CEA-Roche), which avoids the perchloric acid and dialysis steps used in the CEA-Roche assay, has been devised. 2. Comparison of results on 746 plasma samples using our assay with those obtained using the CEA-Roche assay revealed a highly significant correlation coefficient (0.72; p less than 0.00001). 3. A further comparison of results on 373 plasma samples using our assay, but including a preincubation step with goat serum, with those obtained using the CEA-Roche assay also revealed a highly significant correlation coefficient (0.89; 0.00001). The goat serum preincubation step eliminated most of the discordant results in which our assay value was higher than CEA-Roche assay, presumably because of anti-goat antibodies in the patient plasma sample.