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

Reporting Name

CA 19-9, Peritoneal Fluid

Useful For

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

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Peritoneal


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


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

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

Reference Values

An interpretive report will be provided.

Day(s) Performed

Monday through Saturday

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

LOINC Code Information

Test ID Test Order Name Order LOINC Value
199PT CA 19-9, Peritoneal Fluid 50781-4

 

Result ID Test Result Name Result LOINC Value
199PN CA 19-9, Peritoneal Fluid 50781-4
SITEE Site 39111-0

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.

Interpretation

A peritoneal fluid carbohydrate antigen 19-9 (CA 19-9) concentration greater than 32 U/mL is suspicious, but not diagnostic, of a malignancy-related ascites. This clinical decision limit cutoff yielded 44% sensitivity and 93% specificity in a study of 137 patients presenting with ascites. However, ascites caused by malignancies not associated with increase serum CA 19-9 concentrations, including lymphoma, mesothelioma, leukemia, and melanoma, routinely had CA 19-9 concentrations less than 32 U/mL. Therefore, negative results should be interpreted with caution, especially in patients who have or are suspected of having a malignancy not associated with elevated CA 19-9 levels in serum.

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.

Supportive Data

An in-house study was performed to select a clinical decision limit to differentiate between malignancy-related benign causes of ascites with high specificity. The study included 83 cases of benign ascites and 54 cases of malignancy-related ascites. Within the malignancy-related ascites, there were 9 specimens with malignancies known not to secrete carbohydrate antigen 19-9 (CA 19-9) in serum (lymphoma, leukemia, melanoma, sarcoma, and neuroendocrine tumors). Amongst the group that are known to secrete CA 19-9 in serum (n=45), there were the following malignancies: pancreatic, breast, gastric, colon, bladder, cholangiocarcinoma, gynecological cancers, peritoneal carcinomatosis, and hepatocellular carcinoma. Using a clinical decision limit cutoff of greater than 32 U/mL, the specificity was 93% for the benign ascites group. The sensitivity was 49% for those malignancies associated with elevated CA 19-9 in serum.

Clinical Reference

1. Trape J, Molina R, Sant F: Clinical evaluation of the simultaneous determination of tumor markers in fluid and serum and their ratio in the differential diagnosis of serous effusions. Tumour Biol. 2004 Sep-Dec;25(5-6):276-281

2. Sari R, Yildirim B, Sevinc A, Bahceci F, Hilmioglu F: The importance of serum and ascites fluid alpha-fetoprotein, carcinoembryonic antigen, CA 19-9, and CA 15-3 levels in differential diagnosis of ascites etiology. Hepatogastroenterology. 2001 Nov-Dec;48(42):1616-1621

3. Block DR, Algeciras-Schimnich A: Body fluid analysis: clinical utility and applicability of published studies to guide interpretation of today's laboratory testing in serous fluids. Crit Rev Clin Lab Sci. 2013 Jul-Oct;50(4-5):107-124. doi: 10.3109/10408363.2013.844679

4. Jain T, Ram S, Kumar H, Saroch A, Sharma V, Singh H: Ascitic and serum levels of tumor biomarkers (CA 72-4, CA 19-9, CEA AND CA 125) in discrimination of cause of ascites: A prospective study. Arq Gastroenterol. 2022 Apr-Jun;59(2):198-203. doi: 10.1590/S0004-2803.202202000-37

Method Description

The instrument used is a Beckman Coulter DXI 800. The Access GI Monitor assay is a 2-site immunoenzymatic sandwich assay. A sample is added to a reaction vessel along with paramagnetic particles coated with polyclonal goat antibiotin antibody, mouse monoclonal biotin conjugate, and buffered protein solution. After incubation in a reaction vessel, separation in a magnetic field, and washing to remove materials not bound to the solid phase, a monoclonal-alkaline phosphatase conjugate is added. After incubation in a reaction vessel, materials bound to the solid phase are held in a magnetic field, while unbound materials are washed away. The chemiluminescent substrate Lumi-Phos 530 is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the concentration of carbohydrate antigen 19-9 (CA 19-9) in the sample. The amount of analyte in the sample is determined from a stored, multipoint calibration curve.(Package insert: Access GI Monitor Assay, Beckman Coulter, Inc; 2020)

Report Available

1 to 3 days

Specimen Retention Time

14 days

Reject Due To

Gross hemolysis Reject
Gross icterus OK

Method Name

Immunoenzymatic Assay

Secondary ID

61530