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Test ID: CA19 Carbohydrate Antigen 19-9 (CA 19-9), Serum

Reporting Name

Carbohydrate Ag 19-9, S

Useful For

As a potential adjunct for diagnosis and monitoring of pancreatic cancer


Potentially differentiating patients with cholangiocarcinoma and primary sclerosing cholangitis (PSC) from those with PSC alone

Clinical Information

Carbohydrate antigen 19-9 (CA 19-9) is a modified Lewis(a) blood group antigen. CA 19-9 may be elevated in patients with gastrointestinal malignancies such as cholangiocarcinoma, pancreatic cancer, or colon cancer.


Benign conditions such as cirrhosis, cholestasis, and pancreatitis also result in elevated serum CA 19-9 concentrations but in these cases values usually are below 1000 U/mL.


Individuals that are Lewis negative (5%-7% of the population) do not express CA 19-9 due to the lack of the enzyme fucosyltransferase needed for CA 19-9 production. In these individuals, a low or undetectable serum CA 19-9 concentration is not informative regarding cancer recurrence.


Serial monitoring of carbohydrate antigen 19-9 (CA 19-9) should begin prior to therapy to verify post-therapy decreases in CA 19-9 and to establish a baseline for evaluating possible recurrence. Single values of CA 19-9 are less informative.


Elevated values may be caused by a variety of malignant and nonmalignant conditions including cholangiocarcinoma, pancreatic cancer, and colon cancer.

Report Available

1 to 3 days

Day(s) Performed

Monday through Friday

Clinical Reference

1. Torok N, Gores GJ: Cholangiocarcinoma. Semin Gastrointest Dis. 2001 Apr;12(2):125-132

2. Scara S, Bottoni P, Scatena R: CA 19-9: Biochemical and clinical aspects. Adv Exp Med Biol. 2015;867:247-60. doi: 10.1007/978-94-017-7215-0_15

Method Name

Immunoenzymatic Assay

Specimen Type


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.


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.6 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection 

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  90 days
  Ambient  8 hours

Reference Values

<35 U/mL 

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
CA19 Carbohydrate Ag 19-9, S 83084-4


Result ID Test Result Name Result LOINC Value
CA19 Carbohydrate Ag 19-9, S 83084-4


If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-General Request (T239)

-Oncology Test Request (T729)

Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-Neuroimmunology, mml-Neuro-oncology, mml-Pediatric