To investigate the clinical value of serum carbohydrate antigen 19-9 (CA19-9) in the differential diagnosis of benign and malignant biliary system diseases.

Clinical data of 167 patients with biliary system diseases in Department of General Surgery, the First Hospital of Lanzhou University from January 2008 to March 2011 were analyzed retrospectively. The informed consents of all patients were obtained and the ethical committee approval was received. The patients were divided into benign biliary system diseases group (benign diseases group, n=85) and cholangiocarcinoma group (malignant diseases group, n=82). Blood alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), total bilirubin (TB), direct bilirubin (DB), total protein (TP), albumin (ALB) and CA19-9, cancer antigen (CA) 125, carcino-embryonic antigen (CEA), alpha fetoprotein (AFP) were detected after admission to hospital. The indexes of two groups were expressed in M (Q₂₅,Q₇₅), and were compared by Wilcoxon rank sum test. The correlation study was analyzed using Spearman rank correlation analysis. The sensitivity and specificity of serum CA19-9 in diagnosis of cholangiocarcinoma was analyzed using receiver operating characteristic (ROC) curve.

The median level of serum CA19-9 in malignant diseases group was significantly higher than that in benign diseases group [318(41,733) μg/L vs. 43 (15,139) μg/L ; Z=3.736; P<0.05]. Serum CA19-9 in benign diseases group was positively correlated with GGT, ALP, TB, DB and CA125 (r=0.318, 0.335, 0.282, 0.355, 0.387; P<0.05), while was negatively correlated with TP and ALB (r=-0.300,-0.437; P<0.05). CA19-9 in malignant diseases group was positively correlated with ALP, TB, DB and CA125 (r=0.340, 0.394, 0.385, 0.480; P<0.05), while was negatively correlated with ALB (r=-0.389, P<0.05). For all the patients or the jaundice patients, the best positive reference values of CA19-9 in diagnosis of cholangiocarcinoma were both 309 μg/L and the diagnostic sensitivity and specificity were 0.51 and 0.89 in all the patients, 0.57 and 0.85 in the jaundice patients respectively.

The best reference value of CA19-9 in the differential diagnosis of benign or malignant biliary system diseases is 309 μg/L. The diagnostic specificity of serum CA19-9 for cholangiocarcinoma is comparatively high but the sensitivity is moderate.