CEA and CA 19.9 in gastric juice and serum: an aid in the diagnosis of gastric carcinoma?

The aim of this study was to examine the effect of pH on the measurement of carcino-embryonic antigen (CEA), and to assess the efficacy of a combination of serum and gastric juice levels of CEA and Carbohydrate Antigen 19.9 (CA 19.9) in the diagnosis of gastric carcinoma. An initial experiment was performed to determine the effect of pH on the CEA assay. There was a direct linear relationship between pH and the concentration of CEA measured by the assay, such that as hydrogen ion concentration increased, the apparent concentration fell. The correct value was measured at pH 7. Seventy-six normal patients with non-malignant upper gastro-intestinal disorders, and 49 patients with gastric carcinoma were studied, two of which were 'early' gastric carcinomas. All patients underwent upper GI endoscopy, and at this examination blood and gastric juice were taken for analysis. A 'normal range' was constructed as a 95% confidence interval for each of the antigens in serum and gastric juice. The highest sensitivity was achieved using a combination of the two antigens, CEA and CA 19.9 in gastric juice and serum, with a sensitivity of 95.7% and a specificity of 50%. This combination of assays could have value in a screening programme for gastric cancer.