Cancer Antigen 153 (CA 15-3) – Serum
This test measures the level of CA 15-3, a protein sometimes produced by certain types of cancer, including breast cancer and other malignancies.
["CA 15-3 helps monitor cancer progression or recurrence in some patients."]
Key facts at a glance
- LOINC
- 50777-2
- Short code
- CA153PF
- Synonyms
- Cancer Ag15-3 Pcar-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Sterile, leak-proof container without additives (red-top or plain tube); specimen container appropriate for body fluids submitted for cytology and chemistry analysis.
- Units
- N/A
- Ref low
- 15
- Ref high
- 3
- Critical range
- 0.5 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Chemiluminescent Immunoassay (CLIA) or Electrochemiluminescence Immunoassay (ECLIA)
- CPT
- 86300
- SNOMED
- 115341000
- Specimen volume
- Minimum 1-2 mL of pericardial fluid; ideally 5-10 mL to allow for concurrent cytology and chemistry testing.
- Stability
- Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles. Process promptly to prevent cellular degradation.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
What Is CA 15-3 Used For?
CA 15-3 is primarily used as a biomarker to track changes in cancer-related proteins, especially in patients who have already been diagnosed with breast cancer or other cancers that may produce this marker. It can also be used in screening or monitoring for certain conditions, though it is not a standalone diagnostic test for cancer.
How Is the Test Performed?
A blood sample is drawn from a vein in your arm. The blood is then sent to a lab for analysis using an immunoassay method to detect the CA 15-3 protein.
What Does a High or Low Level Mean?
Elevated levels of CA 15-3 may indicate cancer activity, but they can also be influenced by other factors such as pregnancy, obesity, or certain benign conditions. It is not a definitive test for cancer alone and should be interpreted by your healthcare provider in the context of your medical history and other test results.
When Might You Need This Test?
Your doctor may order a CA 15-3 test if you have breast cancer, are being monitored for recurrence, or if you have symptoms that could be linked to cancer. It may also be used in conjunction with other tests for screening or evaluating other conditions.
Reference range
No established reference range for pericardial fluid; CA 15-3 in pericardial fluid is not clinically standardized. Serum reference: <31.3 U/mL (varies by assay manufacturer). Elevated pericardial fluid levels relative to serum may suggest malignant pericardial effusion.N/A
No special patient preparation required for pericardial fluid collection, which is performed via pericardiocentesis by a qualified physician under sterile conditions.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: CA 15-3 plays a role in monitoring certain cancers, particularly breast cancer, but it is not a definitive diagnostic tool. High levels may suggest cancer progression or need for closer observation, while low levels may indicate remission. It is important to discuss results with your healthcare provider, as they will consider the full clinical picture.
Short name
CA 15-3 Blood Test
Frequently asked questions
Why might my CA 15-3 test result be abnormal?
Can CA 15-3 levels change over time?
Is CA 15-3 the same as CA 125?
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