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Test ID 199PT Carbohydrate Antigen 19-9 (CA 19-9), Peritoneal Fluid


Specimen Required


Patient Preparation: For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

Container/Tube: Plain, plastic, screw-top tube

Specimen Volume: 2 mL


Useful For

An adjunct to cytology to differentiate between malignancy-related ascites and benign causes of ascites formation

Method Name

Immunoenzymatic Assay

Reporting Name

CA 19-9, Peritoneal Fluid

Specimen Type

Peritoneal

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Peritoneal Frozen (preferred) 90 days
  Ambient  7 days
  Refrigerated  7 days

Clinical Information

Malignancy accounts for approximately 7% of cases of ascites formation. Malignant disease can cause ascites by various mechanisms, including peritoneal carcinomatosis (53%), massive liver metastasis causing portal hypertension (13%), peritoneal carcinomatosis plus massive liver metastasis (13%), hepatocellular carcinoma plus cirrhosis (7%), and chylous ascites due to lymphoma (7%). The evaluation and diagnosis of malignancy-related ascites is based on the patient clinical history, ascites fluid analysis, and imaging tests.

 

The overall sensitivity of cytology for the detection of malignancy-related ascites ranges from 58% to 75%. Cytology examination is most successful in patients with ascites related to peritoneal carcinomatosis, as viable malignant cells are exfoliated into the ascitic fluid. However, only approximately 53% of patients with malignancy-related ascites have peritoneal carcinomatosis. Patients with other causes of malignancy-related ascites almost always have a negative cytology.

 

Carbohydrate antigen 19-9 (CA 19-9) is a modified Lewis(a) blood group antigen. CA 19-9 may be elevated in the serum patients with gastrointestinal malignancies, such as cholangiocarcinoma, pancreatic cancer, or colon cancer. Measurement of CA 19-9 in ascitic fluid is sometimes used in combination with cytology for detecting malignancy-related ascites.

Reference Values

An interpretive report will be provided.

Cautions

Do not use peritoneal fluid carbohydrate antigen 19-9 (CA 19-9) concentrations as absolute evidence of the presence or the absence of malignant disease. The CA 19-9 result should be interpreted in conjunction with information from the clinical evaluation of the patient and other diagnostic procedures.

 

Approximately 10% of the White population does not express CA 19-9 due to the deficiency of a fucosyltransferase enzyme. Consequently, low values in these individuals are not informative regarding malignancy-related ascites.

 

In some immunoassays, the presence of unusually high concentrations of analyte may result in a high-dose "hook" effect. This may result in a lower or even normal measured analyte concentration. If the reported result is inconsistent with the clinical presentation, the laboratory should be alerted for troubleshooting.

 

In rare cases, some individuals can develop antibodies to mouse or other animal antibodies (often referred to as human anti-mouse antibodies [HAMA] or heterophile antibodies), which may cause interference in some immunoassays. Caution should be used in interpretation of results, and the laboratory should be alerted if the result does not correlate with the clinical presentation.

 

CA 19-9 values are method-dependent; therefore, the same method should be used to serially monitor patients.

Day(s) Performed

Monday through Saturday

Report Available

1 to 3 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

86301

NY State Approved

Yes