Abstract: An immunoassay for a protein that is non-enzymatically glycosylated on the alpha amino group of its N-terminal amino acid, the immunoassay comprising: providing a sample containing the glycosylated protein; reacting the glycosylated protein with a reducing agent so that the sugar residue on the N-terminal amino acid is reduced; contacting the reduced glycosylated protein with an antibody directed to Glc-ol-X which is prepared by immunizing an animal with an immunogen of the formula (Glc-ol-X-L).sub.n -carrier; and detecting or quantitating the reduced glycosylated protein bound to the antibody. In the formula (Glc-ol-X-L).sub.

Abstract: The invention provides a method of screening for gastrointestinal cancer in a mammal comprising: (a) contacting a body fluid taken from the mammal with N3; (b) measuring the amount of antibody to N3 in the body fluid; and (c) determining if the amount of antibody measured in step (b) is higher than the amount of antibody to N3 normally present in the same type of body fluid taken from mammals of the same species that do not have cancer. The invention also provides kits for screening for gastrointestinal cancer in a mammal by measuring the mammal's level of antibodies to N3.