We studied the association between serum levels of an isomeric species of carcinoembryonic antigen and neoplasia of the gastrointestinal tract in 993 patients. With use of an empirically determined threshold, the antigen was found to be elevated in 80.4 per cent of 138 patients with neof other tumors, predominantly lung and breast tumors. Serum levels were elevated in 0.23 per cent of random patients and 0.41 per cent of 725 patients without neoplasia, including those with liver diseases, inflammatory bowel disease and chronic renal disease. The results of this study suggest that this species of carcinoembryonic antigen, and that assay for it offers an improved approach to the diagnosis and management of neoplasia of the gastroinetestinal tract.
