[Does cholestasis change the clinical usefulness of CA 19-9 in pacreatobiliary cancer?]

CA 19-9 is used for diagnosis of gastrointestinal neoplasia, mainly pancreatic and biliary cancer. False positive results have been described in cholestasis.

To establish the clinical value of CA 19-9 in the diagnosis of pancreatic and biliary cancer in patients with and without cholestasis.

Five hundred forty-eight medical records of patients with serum CA 19-9 determination performed from May-1996 to June-1998 were reviewed. Cases were grouped by final diagnosis; malignancy was established by histology or clinical and radiological characteristics. ROC curves were used to calculate ideal cut-off values (ICV) for the test. Cholestasis was defined as bilirrubinemia above 3 mg/dL.

Thirty percent of serum determinations were done in patients with non-pancreatic and non-hepatobiliary benign diseases (only 1.3% with values > or = 100 U/mL). CA 19-9 levels were higher in pancreatic and hepatobiliary malignancy compared to benign diseases of the same origin, as well as in pancreatic cancer when compared with hepatobiliary cancer. ICV for differentiation of malignant hepatobiliary diseases was set around 100 U/mL, with increased specificity when compared with the usual cut-off value (37 U/mL). Cholestasis increased the values of the antigen in malignant and benign diseases and modified the efficacy of the test by increasing sensitivity while decreasing specificity. The ICV for determining resectability in pancreatic tumors was 224 U/mL.

CA 19-9 is a valuable test for diagnosis of malignant pancreato-hepatobiliary disease. Given that cholestasis modifies the operational characteristics of the test, a cut-off value has to be tailored for each patient depending on the clinical setting, so to maintain the usefulness of the marker.