Differences in CEA values determined by EIA and RIA in patients with benign and malignant biliary obstructions.

Serial carcinoembryonic antigen (CEA) levels were determined by both the Roche RIA and Abbott EIA methods in 11 patients with pancreatic cancer (9 with extrahepatic biliary obstruction); 7 with benign extrahepatic obstruction; 26 with colonic cancer without biliary obstruction; and 12 normal, non-smoking controls. The Roche/Abbott CEA ratios in the patients with malignant and benign obstruction (mean ratios = 3.05 and 3.08, respectively), were significantly higher than those in patients with colon cancer without biliary obstruction and in normal controls (mean ratios = 1.35 and 1.06, respectively). Four patients with malignant obstructions were decompressed successfully (bilirubin less than or equal to 1.5 mg/dL); the ratios for two of these patients declined to "normal" (1.0), while the ratios for the other two remained elevated despite decompression. These findings show that some patients with benign or malignant biliary obstruction have elevated CEA levels when measured by the Roche RIA but not with the Abbott EIA.