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CA 19.9 (Cancer-Antigen)

About the test
What is this test done for?
Cancer antigen 19.9 (CA 19.9) is used as a tumor marker to help differentiate between pancreatic cancer and other conditions, as well as to monitor pancreatic treatment response and/or recurrence.
Why is it Done?
Elevated levels of CA 19.9 can be seen in malignant conditions such as bile duct cancers, colorectal cancers, gastric cancers, esophageal cancers, pancreatic cancers, etc. Elevated levels can also be seen in benign conditions such as biliary tract obstruction, cholangitis, inflammatory bowel disease, thyroid disease, etc. CA 19.9 can only be used as a tumor marker if the cancer is producing elevated amounts of it. However, CA 19.9 test is not sensitive or specific enough to use as a screening test for cancer.
When should it be performed?
  • A doctor may order CA 19.9 when a person has been diagnosed with pancreatic cancer and/or has signs and symptoms that may indicate pancreatic cancer.
  • If CA 19.9 is initially elevated in pancreatic cancer, then your doctor may order a series of CA 19.9 tests during cancer treatment to monitor its response and on a regular basis following treatment in order to help detect recurrence.
  • CA 19.9 may sometimes be ordered when a healthcare practitioner suspects bile duct cancer in a person with a bile duct obstruction. Very high CA 19.9 levels are seen when bile duct is obstructed due to some non-cancerous causes; however, these levels fall when the blockage is cleared. It is a good idea to wait at least a week or two in such cases to re-check CA 19.9 levels once the blockage is cleared.
How is it done
A blood sample will be collected from a vein in your arm.
  • The reference range of serum CA 19.9 is less than 37 U/mL.
  • Levels above 37 U/mL may be seen in people with pancreatic cancer, other cancers, and in several other diseases and conditions. The highest levels of CA 19.9 are seen in cancer of the exocrine pancreas, which accounts for 95% of pancreatic cancers.
  • Levels of CA 19.9 that are initially high and then fall over time may indicate that the treatment is successful, while a stable or rising level may indicate the need to change therapies.
Other Tests
The CA 19.9 test may be used, along with other tests such as carcinoembryonic antigen (CEA), bilirubin, and/or a liver test, to help evaluate and monitor a person who has been diagnosed with pancreatic cancer and is undergoing treatment.
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