CA 19-9 is a ganglioside whose synthesis is conditioned by the presence of Lewis blood group antigens. Thus, individuals with a relatively rare blood group negative for Lewis antigens (3-5% of the population) cannot synthesize CA 19-9 and it remains at very low even if a malignancy is present. In such cases the tumor marker CA indicated is 50. Elevated CA 19-9 are seen in 70-80% of cases of pancreatic carcinoma, 50-60% of gastric cancers, 60% of hepatobiliary tumors, 30% of colorectal tumors and in some patients with breast cancer, ovarian, prostate, lung
Indications for CA 19-9 determination:
– diagnosis and monitoring of pancreatic adenocarcinoma, gastric and biliary tumors;
– diagnosis and monitoring of colorectal cancer (second marker after CEA) and ovarian cancer (second marker after CA 125).
Method – ELISA.
Normal values: <35 U / mL.
Marker cannot be used for screening pancreatic carcinoma.
CA 19-9 can be positive in benign diseases, particularly inflammatory bowel disease, cirrhosis, and in autoimmune diseases: rheumatoid arthritis (33%), systemic lupus erythematosus (32%) and scleroderma (33%).