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Interpretive Handbook

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Test 89508 :
Carbohydrate Antigen 19-9 (CA 19-9), Pancreatic Cyst Fluid

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Carbohydrate antigen 19-9 (CA 19-9) is a modified Lewis(a) blood group antigen, and has been used as a tumor marker. Serum CA 19-9 concentrations may be elevated in patients with gastrointestinal malignancies such as cholangiocarcinoma, colon cancer, or pancreatic cancer. While serum CA 19-9 is neither sensitive nor specific for pancreatic cancer, concentrations of CA 19-9 in pancreatic cyst fluid may help determine whether a pancreatic cyst is benign.

 

Cystic lesions of the pancreas are of various types:

-Benign cysts:

 - Inflammatory cysts (pseudocysts)

 - Serous cysts (serous cystadenoma)

 

-Mucinous cysts:

 - Premalignant (mucinous cystadenoma)

 - Malignant (cystadenocarcinoma, intrapapillary mucinous neoplasia)

 

Pancreatic cyst fluid CA 19-9 results should be used in conjunction with imaging studies, cytology, and other cyst-fluid tumor markers, such as carcinoembryonic antigen and amylase.

Useful For Suggests clinical disorders or settings where the test may be helpful

As an adjunct in the assessment of pancreatic cysts, when used in conjunction with carcinoembryonic antigen, amylase, imaging studies and cytology

Interpretation Provides information to assist in interpretation of the test results

Cyst fluid carbohydrate antigen 19-9 (CA19-9) concentrations < or =37 U/mL indicate a low risk for a mucinous cyst, and are more consistent with serous cystadenoma or pseudocyst. The sensitivity and specificity are approximately 19% and 98%, respectively, at this concentration.

 

Correlation of these test results with cytology and imaging is recommended.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Carbohydrate antigen 19-9 (CA 19-9) and other tumor markers are not specific for malignancy and CA 19-9 testing has limited utility when used as the sole tumor marker test. Other tests (eg, carcinoembryonic antigen, amylase, cytology) should be performed in conjunction with CA 19-9 for assessing pancreatic cyst aspirates.

 

A low or negative result (<5 U/mL) may be uninformative or misleading since some individuals (Lewis nonsecretors) do not produce the CA 19-9 antigen. In such cases, a serum CA 19-9 measurement is necessary to verify that the patient is (or is not) a CA 19-9 secretor.

 

This test should not be ordered for pancreatic fluid of noncyst origin (eg, pancreatic duct fluid, peripancreatic fluid) since reference values have not been established for this specimen type. Contact Mayo Medical Laboratories for ordering assistance.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Snozek CL, Jenkins SM, Bryant SC, et al: Analysis of CEA, CA19-9 and amylase in pancreatic cyst fluid for diagnosis of pancreatic lesions. Clin Chem 2008;54(6 Suppl S):A126-127

2. van der Waaij LA, van Dullemen HM, Porte RJ: Cyst fluid analysis in the differential diagnosis of pancreatic cystic lesions: a polled analysis. Gastrointest Endosc 2005;62:383-389

3. Khalid A, Brugge W: ACG practice guidelines for the diagnosis and management of neoplastic pancreatic cysts. Am J Gastroenterol. 2007 Oct;102(10):2339-2349


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