CA 19-9 (Carbohydrate Antigen 19-9) has greatest utility in the management of patients with pancreatic and other gastrointestinal cancers. CA 19-9 is frequently elevated in the serum of subjects with various other gastrointestinal carcinomas such as colorectal, gastric and hepatitis carcinomas. Serial testing for patient CA 19-9 should be used in conjunction with other clinical methods for monitoring cancer. CA 19-9 values obtained by other methods cannot be used interchangeably due to differences in assay methods and reagent specificity.
Elevations of CA 19-9 have been reported in individuals with non-malignant conditions such as cirrhosis, hepatitis, pancreatitis and various other gastrointestinal diseases. Elevated levels may also be found in cystic fibrosis. Although not recommended, if used as a screening test, care must be taken in the interpretation of the results.