Glycoantigen 19-9, a glycoprotein on cell membranes, is one of the tumor markers that are significantly elevated in gastrointestinal tract tumors, such as pancreatic, gastric, colon, and liver cancers, and in gynecological tumors, such as ovarian and breast cancers. Therefore, glycoantigen 19-9 is mostly used as a monitoring indicator for tumor treatment, and follow-up for the presence of tumor recurrence, but not as a diagnostic indicator. Because some non-neoplastic diseases also show increased CA19-9 levels, such as acute and chronic pancreatitis, cholecystitis, renal insufficiency, hepatic insufficiency, and diabetes mellitus. In addition, some patients with rheumatic immune diseases who have autoantibodies in their bodies or who have been successfully vaccinated with certain vaccines may also show elevated CA19-9 test results.