CA 19-9: what it is, what it tells you and when it’s tested

CA 19-9 is a substance that some cells, for example in the pancreas and bile ducts, make in small amounts. Some cancers, mainly of the pancreas and bile ducts, make more of it. But it also often rises for benign reasons, such as a stone blocking the bile or pancreatitis. It is not used to look for cancer in people who feel well: it is mainly used to follow a disease that is already known.

When it’s tested

It is usually ordered by a specialist for people with cancer of the pancreas or bile ducts: before surgery, to understand the situation better, and then to follow treatment and check-ups.

It is not a screening test. Guidelines advise against it in people who feel well: in someone without symptoms, a high CA 19-9 is almost never cancer, and some cancers do not raise it.

That is why Rosa does not test it. The Rosa panel is a general prevention check-up, not a cancer test. It does measure bilirubin, gamma GT and alkaline phosphatase, which show how your liver and bile ducts are working.

What it tells you, and what it does not

A high CA 19-9 does not mean cancer. Gallstones, an inflamed gallbladder, pancreatitis and blocked bile often raise it, sometimes by a lot. Diabetes, liver conditions and autoimmune conditions can raise it too.

A normal CA 19-9 does not rule out cancer. And some people, for a harmless genetic reason, do not make it at all: in them it always stays very low.

What matters most is how it changes over time, in the same person and at the same lab.

Your doctor reads it together with other tests:

• Bilirubin: It rises when bile is blocked, a common cause of high CA 19-9
• Gamma GT: It shows whether your bile ducts are under strain
• Lipase: It rises with pancreatitis, which also raises CA 19-9
• HbA1c: Diabetes can raise CA 19-9 a little

Normal CA 19-9 levels

The lab decides what is normal. Many lab reports give a CA 19-9 below 37 U/mL.

If bile is blocked, for example by a stone, CA 19-9 can reach very high values even without cancer. In that case the value is read with great caution.

Each lab uses its own method, and the same blood can give slightly different numbers at two labs. To follow it over time, it is best to use the same lab every time.

Why CA 19-9 can be high

The cause is often benign, and involves the bile ducts or pancreas.

• Gallstones and an inflamed gallbladder: Gallstones and gallbladder inflammation can raise it.
• Blocked bile: If bile cannot flow and your skin turns yellow, it can rise a lot, whatever the cause. A bile duct infection raises it too.
• Pancreatitis: Both acute and chronic.
• Liver conditions: Hepatitis, chronic hepatitis and cirrhosis can raise it.
• Diabetes: Diabetes, and the kidney damage it can cause, can raise it.
• Other conditions: Rheumatic and autoimmune conditions, some benign lung conditions, cystic fibrosis.
• Some cancers: Mainly of the pancreas and bile ducts, but also of the stomach, colon and others.

If you have cancer of the pancreas or bile ducts

This is where CA 19-9 really helps. Before surgery it gives an idea of the situation. During treatment, measured at regular intervals set by your oncologist, it helps show whether the treatment is working.

A rise always needs to be confirmed with other tests, such as a CT scan. CA 19-9 alone does not decide treatment.

If your bile was blocked, your doctor has CA 19-9 repeated once the blockage has cleared.

If your CA 19-9 is above the limit

Try not to worry: it is common, and often benign. Where to start:

• Show the report to the doctor who ordered it, or to your GP.
• Tell them whether you have gallstones, have had pancreatitis, or have diabetes or a liver condition.
• Your doctor often has it repeated, at the same lab, together with liver tests and an ultrasound scan.
• Only your doctor decides whether more tests are needed. A high result on its own is not enough for a diagnosis.

When to talk to a doctor

Talk to your doctor if:

• Your CA 19-9 is above the limit on your report.
• You have had cancer and your CA 19-9 rises from one check-up to the next.
• Your skin or the whites of your eyes turn yellow, your urine is dark or your stools are pale: see your doctor soon.
• Your skin turns yellow with a high fever and shivering, or you have severe tummy pain going through to your back: call 112 or go to the emergency department.

Frequently asked questions

High CA 19-9: what are the benign causes? The most common are gallstones, an inflamed gallbladder, blocked bile and pancreatitis. Diabetes, liver conditions and autoimmune conditions can raise it too.

What are normal CA 19-9 levels? Many lab reports give a value below 37 U/mL. The range on your own report is what counts.

CA 19-9 and gallstones: is there a link? Yes. Gallstones and an inflamed gallbladder can raise it, and if a stone blocks the bile the value can rise a lot. Once the problem is solved, your doctor has it repeated.

Can CA 19-9 find pancreatic cancer? Not in people who feel well. In someone without symptoms, a high value almost always has another cause, and some cancers do not raise it. It is mainly used to follow people who already have a diagnosis.

Does Rosa test CA 19-9? No. Rosa is a general prevention check-up and does not include tumour markers. It measures bilirubin, gamma GT and alkaline phosphatase, which show how your liver and bile ducts are working. If your doctor thinks CA 19-9 is useful, they order it separately.

Sources

• AGENAS (Italian National Agency for Regional Health Services), circulating tumour markers in oncology: a guide to appropriate clinical use, summarising guidelines including AIOM, ESMO and ASCO. Quaderno di Monitor, 2016. AGENAS 2016
• Locker and colleagues, ASCO 2006 update of recommendations for the use of tumor markers in gastrointestinal cancer. Journal of Clinical Oncology, 2006. PMID 17060676
• Ballehaninna and Chamberlain, the clinical utility of serum CA 19-9 in the diagnosis, prognosis and management of pancreatic adenocarcinoma: an evidence based appraisal. Journal of Gastrointestinal Oncology, 2012. PMID 22811878