Cancer Antigen 19-9 (CA 19-9) in Aspirate Fluid
This test measures a protein linked to certain cancers, often checked in fluid collected from a procedure like a biopsy or drainage of a fluid-filled mass.
["CA 19-9 helps detect or monitor pancreatic, biliary, or other cancers by tracking protein levels in aspirate samples."]
Key facts at a glance
- LOINC
- 97750-4
- Short code
- CA19-9
- Synonyms
- Cancer Ag19-9 Aspirate-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top tube for serum collection; sterile leak-proof container for aspirate/fluid specimens
- Units
- N/A
- Ref low
- 0
- Ref high
- 37
- Critical range
- 0.5 N/A – 1000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Immunoassay (Chemiluminescent or Electrochemiluminescent)
- CPT
- 86301
- SNOMED
- 45261009
- Specimen volume
- 1-2 mL of aspirate or 1 mL of serum minimum
- Stability
- Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or lower): 3 months. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 50
- Lipemia max
- 100
- Icterus max
- 25
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your doctor may order this test if you’re at risk for cancer, have symptoms like abdominal pain or unexplained weight loss, or if fluid has been collected during a procedure (e.g., fine-needle aspiration). It helps assess whether cancer cells are present in the fluid or if cancer has spread.
What to Expect Before the Test
No special preparation is needed unless your doctor specifies. You may need to fast for 8–12 hours before the procedure if fluid is collected via a needle. Follow any instructions given by your healthcare team.
What the Test Results Mean
Higher-than-normal levels may suggest cancer or other conditions affecting fluid production. Very low levels could indicate normal fluid or certain non-cancerous conditions. Results are interpreted by your doctor in the context of your medical history and symptoms.
Common Conditions Monitored
CA 19-9 is often used alongside other tests to monitor pancreatic cancer, biliary tract cancer, or metastatic disease. It may also be checked in patients with unexplained abdominal masses or symptoms.
Reference range
<37 U/mL (commonly cited reference cutoff; reference values may vary by laboratory and assay manufacturer)N/A
No fasting required. Patient should be informed that CA 19-9 is a tumor-associated antigen and is not recommended as a screening test for cancer in the general population.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated CA 19-9 in aspirate fluid is strongly associated with malignant cells, particularly in pancreatic or biliary cancers. It’s not a definitive test alone but supports diagnosis when combined with imaging, biopsy results, and clinical findings. False positives can occur in infections or benign conditions, so results must be reviewed carefully by a healthcare provider.
Short name
CA 19-9 (Aspirate)
Frequently asked questions
Will this test hurt?
How soon will I get my results?
Can I drink or eat before the 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.
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