Kumar M S, Carl K J, Deodhar S D
Clin Chem. 1979 Feb;25(2):314-8.
Values obtained by the indirect and the direct assays for carcinoembryonic antigen by use of the "CEA Roche" method and reagents differ significantly. In 32 samples the latter method gave values almost twofold those obtained by the former. The mean ratio for direct/indirect was 1.9 +/- 0.6. Analytical recovery experiments on samples to which known amounts of the antigen had been added showed a similar disparity. A simple modification of these two procedures, involving addition of normal human plasma (containing less than 2.0 microgram of the antigen per liter) to standards, eliminated this discrepancy. In the indirect method, standards were added to normal human plasma, then extracted with perchloric acid before assay. In the direct assay normal human plasma instead of goat serum, was added to standards. With these modifications the analytical recoveries of added CEA by the indirect and direct methods were 87 +/- 17% and 99.7 +/- 8%, respectively, and the mean ratio between two methods was 1.2 +/- 0.4.
采用“罗氏癌胚抗原（CEA Roche）”方法及试剂，通过间接法和直接法检测癌胚抗原所获得的值存在显著差异。在32个样本中，后一种方法得出的值几乎是前一种方法的两倍。直接法/间接法的平均比值为1.9±0.6。对添加了已知量抗原的样本进行的分析回收率实验也显示出类似的差异。对这两种方法进行简单修改，即在标准品中加入正常人血浆（每升含抗原量低于2.0微克），消除了这种差异。在间接法中，将标准品加入正常人血浆中，然后在检测前用高氯酸提取。在直接法中，向标准品中加入正常人血浆而非山羊血清。经过这些修改后，间接法和直接法对添加的癌胚抗原的分析回收率分别为87±17%和99.7±8%，两种方法之间的平均比值为1.2±0.4。
