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Cancer Antigen 19-9 (CA 19-9) with Serum Specimen

Published: August 9, 2026Updated: August 17, 2026

This test measures the level of a protein called CA 19-9, which may be produced by certain types of cancerous cells. It is often used to monitor treatment progress or detect recurrence in patients with pancreatic, biliary, or other gastrointestinal cancers.

Quick summary

["CA 19-9 helps track cancer spread and response to treatment but isn’t a standalone diagnostic test for cancer."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
50779-8
Short code
CA199-CSF
Synonyms
Cancer Ag19-9 CSF-aCnc
Category
chemistry
Sample
csf
Container
Sterile CSF collection tube (polypropylene), tube #3 or #4 recommended to minimize blood contamination
Units
N/A
Ref low
19
Ref high
9
Critical range
0.5 N/A – —
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Immunoassay (Electrochemiluminescence Immunoassay or Chemiluminescent Microparticle Immunoassay)
CPT
86316
SNOMED
71600-1
Specimen volume
1.0-2.0 mL of cerebrospinal fluid
Stability
Room temperature: 4 hours; Refrigerated (2-8°C): 24 hours; Frozen (-20°C or below): 3 months. Avoid repeated freeze-thaw cycles.
Hemolysis max
200
TAT
24–72 hours
Order
routine

What Is CA 19-9 Used For?

CA 19-9 is primarily used as a biomarker to monitor certain cancers, particularly pancreatic, biliary tract, and some gastrointestinal cancers. It can help detect early signs of cancer recurrence or spread (metastasis) and assess how well treatment is working. However, it is not used to diagnose cancer in isolation.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. The serum portion of your blood is then analyzed in a lab to measure the CA 19-9 protein levels. This test is typically done using an immunoassay method to detect and quantify the protein.

Why Might You Need This Test?

You may need a CA 19-9 test if you have a history of cancer, particularly pancreatic or biliary tract cancer, or if you are undergoing treatment for these conditions. It may also be used to check for cancer spread to other parts of the body or to monitor treatment effectiveness over time.

What Do Results Mean?

Higher than normal levels of CA 19-9 can indicate cancer or cancer spread. However, elevated levels can also occur in non-cancerous conditions, such as chronic liver disease or pancreatitis. Your healthcare provider will interpret results in the context of your medical history and other test results.

Reference range

Not well established in CSF; CSF CA 19-9 is generally not detectable or present at very low levels (<1.0 U/mL) in healthy individuals. Results should be interpreted in conjunction with clinical findings and imaging studies.N/A

Specimen: csf

No special patient preparation required. Fasting is not necessary. Inform physician of any medications, recent procedures, or known tumor history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: CA 19-9 plays a critical role in the surveillance of certain cancers, especially pancreatic and biliary cancers. While it is not a definitive diagnostic test, rising levels can signal disease progression or recurrence, prompting further investigation. It is often used alongside other diagnostic tools and imaging studies for comprehensive evaluation.

Short name

CA 19-9 Blood Test

Frequently asked questions

What causes CA 19-9 levels to be elevated?
Elevated CA 19-9 levels can be associated with pancreatic, biliary, or gastrointestinal cancers, but they may also occur in non-cancerous conditions such as chronic liver disease, pancreatitis, or certain infections.
Can CA 19-9 levels change with treatment?
Yes, CA 19-9 levels can change with cancer treatment. A decrease in levels often suggests the cancer is responding to treatment, while an increase may indicate disease progression or recurrence. Your doctor will monitor these changes over time.
Is CA 19-9 the only test used to diagnose cancer?
No, CA 19-9 is not the only test used for cancer diagnosis. It is typically used alongside imaging studies (such as CT scans or MRIs), physical exams, and other biomarkers to provide a complete picture of your health and disease status.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy