Rectal mucosal quantitative galactose oxidase-Schiff reaction as an early detection biomarker for colorectal cancer: comparison to fecal occult stool blood test.

The galactose oxidase-Schiff (GOS) reaction detects D-galactose-β-[1,3]-N-acetyl-D-galactosamine. This is a T-antigen expressed in mucus from malignant cells and colonic mucosa adjacent to cancer but not in normal mucosa. Previous studies using a qualitative GOS assay proved to be of limited value for the detection of colorectal neoplasia.