Serum/plasma concentration of cancer antigen 50 (CA 50)
This test measures the level of a specific protein, CA 50, which may be produced by certain types of cancer. It’s often used to help monitor cancer progression or response to treatment.
["CA 50 helps track cancer growth or spread in certain cancers, but it’s not a definitive diagnostic test alone."]
Key facts at a glance
- LOINC
- 2013-1
- Short code
- CA50
- Synonyms
- Cancer Ag50 SerPl Ql
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top tube; plasma may be collected in heparin or EDTA tubes
- Units
- N/A
- Ref low
- 0
- Ref high
- 25
- Critical range
- 0.5 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Immunoassay (e.g., ELISA, chemiluminescent immunoassay, or radioimmunoassay)
- CPT
- 86316
- SNOMED
- 115341005
- Specimen volume
- 1-2 mL of serum or plasma
- Stability
- Stable for 24 hours at room temperature (20-25°C); up to 7 days at 2-8°C; for longer storage, freeze at -20°C or below for up to 3 months. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 100
- Lipemia max
- 100
- Icterus max
- 50
- TAT
- 24–72 hours
- Order
- routine
What Is CA 50 Used For?
CA 50 is primarily used as a biomarker in the monitoring of advanced ovarian cancer, pancreatic cancer, and other malignancies. It may be ordered to assess disease progression, recurrence, or treatment effectiveness, especially when other markers are less informative.
How Is the Test Performed?
A blood sample is drawn from a vein in your arm. The blood is then processed to separate serum or plasma, which is sent to a lab for analysis using an immunoassay method to detect and quantify CA 50 levels.
What Does a CA 50 Test Tell You?
While CA 50 can indicate the presence of certain cancers, it is not a standalone test for diagnosis. Elevated levels may suggest cancer activity, but they can also be influenced by other factors like inflammation or certain medications. Your healthcare provider will interpret results in the context of your medical history and other tests.
When Might You Need a CA 50 Test?
You may be asked to have a CA 50 test if you have a history of ovarian or pancreatic cancer, or if you’re undergoing treatment for these conditions. It may also be used in follow-up care to monitor changes in your cancer status over time.
Reference range
Negative: < threshold value established by laboratory (typically < 25 U/mL; assay-dependent). Positive: ≥ threshold value. Reference values vary by assay manufacturer.N/A
No fasting required. Avoid hemolyzed, lipemic, or icteric specimens as they may interfere with assay performance. Patient should be informed that this test is a screening/monitoring aid and not a definitive diagnostic test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
CA 50 Tumor Marker
Frequently asked questions
Why was I asked to have this test?
Can CA 50 levels change without cancer?
How often should I get this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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.
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Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy