CA 19-9 is a tumour-associated glycoprotein mucin that bears a specific carbohydrate epitope, the sialylated Lewisa blood group antigen. The assay is based upon a monoclonal antibody, 1116-NS-19-9 which recognises this carbohydrate antigenic determinant. Approximately 7 % of the population who have the phenotype Lewisa negative are prevented by their genetic constitution from synthesising CA 19-9 antigen. Serum CA 19-9 concentrations are elevated in 70-92 % of patients with pancreatic carcinomas. This marker may also prove helpful in monitoring treatment response in other CA 19-9 positive carcinomas. CA 19-9 may be elevated in cancers, including hepatocellular, gastric, colorectal, lung and gall bladder cancers. A variety of conditions, including biliary obstruction, cholestasis, cholangitis, hepatic cirrhosis, cystic fibrosis, acute and chronic pancreatitis, may also cause elevation of CA 19-9.
Diagnosis: since CA 19-9 may be elevated in benign conditions it is not recommended for screening purposes and diagnostic utility should be limited to case finding in symptomatic patients in conjunction with pancreatic imaging.
Prognosis and staging: baseline CA 19-9 can be used to guide treatment and follow-up and may have a prognostic value in absence of cholestasis. CA 19-9 carries independent predictive value for successful resection of pancreatic cancer and overall survival.
Treatment monitoring: CA 19-9 measurements are recommended in conjunction with imaging to monitor response to therapy.
Surveillance: studies have indicated that CA19-9 has high sensitivity for detection of relapse following pancreatectomy.
SST (gold top) preferred, serum (red top) accepted