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Subject: Cancer Antigen 19-9 (CA 19-9)
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CA 19-9 is a modified Lewis(a) blood group antigen and has been used as a tumor marker. It is shown to be elevated in sera of some patients with GI tumors.
Normal value: <35 U/mL.
Detection, diagnosis, and prognosis of pancreatic cancer
Monitor response to therapy (e.g., postsurgical recurrence correlates with increased concentrations)
May be a useful adjunct to CEA for diagnosis and to detect early recurrence of certain cancers
May indicate development of cholangiocarcinoma in patients with primary sclerosing cholangitis
Carcinoma of the pancreas (80%).
Pancreatitis—concentrations are usually <75 U/mL but are much higher in pancreatic cancer.
Hepatobiliary cancer (22–51%).
Gastric cancer (42%).
Colon cancer (20%) is associated with very poor prognosis.
Noncancerous conditions that may elevate include cirrhosis, cholangitis, hepatitis, pancreatitis, and nonmalignant GI diseases.
Can be considered as a marker of MTC dedifferentiation and diseases aggressiveness.
Individuals with blood group antigen Le a-b- do not synthesize CA 19-9 (5–10% of population).
No value in screening because its PPV <1%. However, levels of >1,000 U/mL have 97% PPV.
The CA 19-9 levels in a given specimen determined with assays from different manufacturers can vary due to differences in assay methods and reagent specificity and cannot be used interchangeably. If, in the course of monitoring a patient, the assay method used is changed, additional sequential testing should be carried out to confirm baseline values.