CA 19-9
CA 19-9 is a blood test used to measure levels of a protein that can be elevated in some types of cancer, particularly pancreatic cancer. It's often used to monitor pancreatic cancer treatment and for detecting potential recurrence. However, CA 19-9 is not a screening test for cancer and can be elevated in other conditions, including pancreatitis, gallstones, and certain liver diseases.
What it is:
CA 19-9, or carbohydrate antigen 19-9, is a protein found in the blood. It's a type of tumor marker, meaning it can be produced by cancer cells or, in some cases, by normal cells in response to cancer.
Why it's tested:
Doctors may order a CA 19-9 test for a variety of reasons, including:
- Monitoring pancreatic cancer: MedlinePlus (.gov) explains that it can be used to monitor how well pancreatic cancer treatment is working and to detect if the cancer has returned after treatment.
- Assessing other cancers: CA 19-9 levels can be elevated in some other types of cancer, including those of the bile duct, colon, stomach, ovaries, and bladder, MedlinePlus (.gov) notes.
- Predicting how cancer might behave: CA 19-9 levels can be used to help predict how cancer might behave over time.
Limitations:
- Not a screening test: CA 19-9 is not used as a screening test for cancer.
- Non-cancerous conditions: Elevated CA 19-9 levels can also be caused by non-cancerous conditions, such as pancreatitis, gallstones, liver disease, and certain other conditions, MedlinePlus (.gov) explains.
- False negatives: Some people don't produce CA 19-9 at all, making the test inaccurate for them.
- False positives: CA 19-9 levels can be elevated in some cases of biliary obstruction, even without pancreatic cancer.
Interpreting results:
- CA 19-9 levels are usually measured in units per milliliter (U/mL). A higher than normal result does not automatically mean that a person has cancer, MedlinePlus (.gov) says. The results should always be interpreted in the context of other medical tests and the patient's overall clinical picture.