Carbohydrate Antigen 19-9 (CA 19-9), Peritoneal Fluid
Use
This test is useful as an adjunct to cytology to differentiate between malignancy-related ascites and benign causes of ascites formation. Malignancy accounts for approximately 7% of ascites cases, often caused by mechanisms such as peritoneal carcinomatosis or liver metastasis. By measuring CA 19-9 levels in ascitic fluid, it's possible to aid in the diagnosis of malignancy-related ascites. Elevated levels of CA 19-9 can indicate gastrointestinal malignancies such as cholangiocarcinoma and pancreatic cancer, making this measurement a valuable tool alongside cytology.
Special Instructions
For 12 hours prior to specimen collection, patients should not take multivitamins or dietary supplements containing biotin (vitamin B7). If not ordering electronically, complete, print, and send an Oncology Test Request (T729) with the specimen. Specimen retention time is 12 months after testing.
Limitations
The test should not be used as absolute evidence of malignant disease presence or absence. Interpretation should consider the clinical evaluation and other diagnostic procedures. Approximately 10% of the White population doesn't express CA 19-9 due to an enzyme deficiency. High concentrations of analyte may cause a 'hook' effect in some immunoassays, possibly leading to inaccurate readings. Peritoneal washings are not acceptable; interference from human anti-mouse antibodies or heterophile antibodies may also affect results.
New York Approved
Methodology
Immunoassay (Immunoenzymatic Assay)
Biomarkers
LOINC Codes
- 50781-4
- 50781-4
- 39111-0
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Body Fluid
Volume
2 mL
Minimum Volume
0.5 mL
Container
Plain, plastic, screw-top tube
Collection Instructions
Sources: Peritoneal, abdominal, ascites, paracentesis fluid. Peritoneal washings are not acceptable.
Patient Preparation
For 12 hours before specimen collection, patient should not take multivitamins or dietary supplements containing biotin (vitamin B7).
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 7 days |
| Frozen | 90 days |