CA 19‑9, Peritoneal Fluid
Use
Measurement of carbohydrate antigen 19‑9 in peritoneal (ascitic) fluid may serve as an adjunct to cytology for differentiating between malignancy‑related ascites and benign causes of ascites formation. Elevated CA 19‑9 levels in ascitic fluid, particularly above 32 U/mL, are suspicious—though not diagnostic—for malignancy‑related ascites, offering higher specificity in combination with clinical evaluation and imaging.
Special Instructions
Patient should refrain from taking multivitamins or dietary supplements containing biotin (vitamin B7) for 12 hours prior to specimen collection. Peritoneal washings are not acceptable as a specimen type. If ordering manually, complete and submit an Oncology Test Request (T729) with the specimen.
Limitations
Results are method‑dependent and should not be used in isolation to diagnose malignancy. A negative result does not exclude malignancy, particularly for tumors not associated with elevated CA 19‑9 (e.g., lymphoma, mesothelioma, leukemia, melanoma). Approximately 10% of individuals (e.g., persons lacking Lewis antigen) may not express CA 19‑9, limiting interpretability. High analyte concentrations may produce a ‘‘hook’’ effect resulting in falsely low measurements; heterophile antibodies (e.g., HAMA) may interfere, causing erroneous results.
New York Approved
Methodology
Immunoassay (Immunoenzymatic Assay)
Biomarkers
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Other
Volume
Not provided
Minimum Volume
Not provided