Imperial Collage Healthcare

Cancer antigen 19-9 (CA 19-9)


Test Background
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.


Clinical Indications

  • Pancreatic cancer
    • 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.


Reference Range

<37 kIU/L


Sample Required
Serum (red top) preferred, SST (gold top) acceptable


Sample Volume
0.5 mL


Turnaround Time
4 days


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