What can cause abnormal levels of CA 19-9?
Abnormal levels of CA 19-9 can arise from a variety of conditions. Here are the primary reasons for elevated CA 19-9 levels:
Pancreatic Cancer: The most common association, where levels often correlate with tumor burden and disease progression.
Bile Duct Cancer: Elevated levels can also be seen in cholangiocarcinoma.
Gastrointestinal Cancers: Including colorectal and gastric cancers.
Liver Diseases: Such as hepatitis and cirrhosis can cause mildly elevated CA 19-9 levels.
Benign Conditions: Acute and chronic pancreatitis, bile duct obstruction, and inflammatory bowel diseases can also cause increased levels.
It is important to note that not all people with pancreatic cancer will have elevated CA 19-9.
About 5-10% of the population lack the Lewis antigen, necessary for the production of CA 19-9, and will not show elevated levels even in the presence of pancreatic cancer. This limitation emphasises the necessity of using CA 19-9 alongside other diagnostic procedures.
What is the CA 19-9 blood test used for?
The CA 19-9 blood test measures the level of the CA 19-9 antigen, primarily used to monitor and manage pancreatic cancer. It helps in evaluating the effectiveness of treatments such as surgery, chemotherapy, and radiation therapy.
Elevated CA 19-9 levels can indicate cancer recurrence or progression, making it a valuable tool for ongoing patient management.
Beyond pancreatic cancer, CA 19-9 levels can also be elevated in other gastrointestinal cancers, such as bile duct and colorectal cancers. However, it's crucial to use this test in conjunction with other diagnostic tools because elevated CA 19-9 can also occur in benign conditions like pancreatitis and liver disease.
Who should get a CA 19-9 blood test?
Individuals presenting symptoms suggestive of pancreatic or other gastrointestinal cancers, such as jaundice, unexplained weight loss, or persistent abdominal pain, might be recommended for a CA 19-9 blood test. This test helps in the initial assessment and staging of these cancers, offering insights into the disease's extent and progression.
Additionally, patients already diagnosed with pancreatic cancer often undergo CA 19-9 testing regularly to monitor their response to treatment and to detect any signs of recurrence. By tracking CA 19-9 levels over time, your doctor can adjust treatment plans as necessary, ensuring a more personalised and effective approach to cancer management.
How are CA 19-9 test results interpreted?
CA 19-9 test results are typically expressed in units per milliliter (U/mL), with normal levels being below 35 U/mL. This is the current (August 2024) reference range for our laboratory, and may change.
Results above this threshold might suggest the presence of malignancy, particularly in the pancreas, but interpretation must consider your overall clinical picture and other diagnostic findings.
Elevated CA 19-9 levels do not automatically confirm cancer. They can occur in benign conditions like pancreatitis, liver disease, and bile duct obstruction. Thus, while elevated levels can prompt further investigation, they should be interpreted with caution. Please consult your GP.
What can cause elevated CA 19-9 levels besides cancer?
Elevated CA 19-9 levels can be caused by several benign conditions, including pancreatitis, which is inflammation of the pancreas, liver cirrhosis, and bile duct obstruction. These conditions can lead to increased production or decreased clearance of the CA 19-9 antigen, resulting in higher blood levels.
Inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis, can also elevate CA 19-9 levels.
Therefore, elevated CA 19-9 in the absence of other cancer indicators require a for a comprehensive diagnostic approach, rather than just a blood test.
What are the limitations of the CA 19-9 blood test?
The CA 19-9 blood test, while useful, has limitations. It is not cancer-specific, as elevated levels can be seen in benign conditions, which can lead to false positives. Additionally, not all people with pancreatic cancer will have elevated CA 19-9 levels, particularly those lacking the Lewis antigen, which is necessary for CA 19-9 expression.
Due to these limitations, CA 19-9 should not be used as a standalone diagnostic tool. It is most effective when used in conjunction with other diagnostic methods, such as imaging studies (CT scans, MRIs) and biopsies.
