Carcinoembryonic antigen (CEA): A comparison of the Farr and Z-gel methods for CEA detection in benign and malignant diseases

Abstract

Carcinoembryonic Antigen (CEA) was assayed in the serum of 177 patients with the Farr radioimmunoassay and in the plasma of 166 patients with the Z-gel radioimmunoassay. Patients were classified into four groups according to diagnosis: (I: gastro-intestinal (GIT) cancer; II: non GIT cancer; III: benign GIT disease; IV: benign non GIT disease). Abnormal CEA levels (> 2·5 ng/ml) were obtained in 66%, 57%, 39% and 15% with the Farr technique, and in 70%, 44%, 47% and 12% with the Z-gel method in the diagnosis groups I, II, III and IV respectively. The same aliquots of blood was also assayed in 72 patients with both techniques; results agreed in 87% of the cases. Statistical evaluation of the data indicate no difference between the two methods. The range of probability of a false negative CEA value is high no matter which technique is used. This limitation is partially circumvented by raising the considered normal CEA value to higher levels.