Carbohydrate antigen 19-9 (CA 19-9)

What it measures

CA 19-9 is a carbohydrate antigen shed by some gastrointestinal tumours. It is used to monitor pancreatic and biliary cancer and to support assessment of resectability.

Specimen and preparation

• Specimen: Serum or lithium-heparin plasma
• Tube: Gold top

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Pancreatic cancer
• Cholangiocarcinoma and gallbladder cancer
• Biliary obstruction and cholangitis (benign)
• Gastric and colorectal cancer
• Pancreatitis and cirrhosis

Causes of low values

• Lewis-antigen-negative individuals (about 5–10%) cannot produce it

Method

Chemiluminescent immunoassay

Good to know

Interpret only after relieving jaundice, which can raise levels markedly.

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