Respective Value of Alkaline Phosphatase, Gamma-glutamyl Transpeptidase and 5′ Nucleotidase Serum Activity in the Diagnosis of Cholestasis

We studied the value of alkaline phosphatase (AP), gamma-glutamyl transpeptidase (GGT), and 5'-nucleotidase (5'-NU) activities in the diagnosis of intrahepatic (IHC) versus extra-hepatic cholestasis (EHC). Eighty patients were included prospectively. All presented with cholestasis as defined by a concomitant increase in at least two of three cholestatic enzymes (AP, GGT, 5'-NU), a low cytolytic ratio (alanine aminotransferase/AP [xN/xN] < or = 5), and no evidence for associated liver tumor. We compared 43 patients with IHC due to chronic liver disease to 37 patients with EHC due to main bile duct obstruction. Fasting blood samples for activity determination (AP, GGT, 5'-NU) were taken before performing liver biopsy in cases of IHC and before endoscopic or surgical management in cases of EHC. Enzyme activities were compared using univariate and multivariate analysis. AP (276 IU/L [35-3,140] vs. 123 IU/L [37-699]: p < 0.0001), GGT (595 IU/L [98-5,200] vs. 211 IU/L [38-925]; p < 0.0001), and 5'-NU (32 IU/L [10-142] vs. 16 IU/L [4-107]: p < 0.0003) were significantly higher in EHC when compared to IHC. Only in GGT and 5'-NU activities were independent variables significantly linked to the mechanism of cholestasis. In IHC, the ratio GGT/5'-NU (xN/xN) was significantly lower than in EHC (2.8 [0.7-7.2] vs. 3.7 [1.8-10.5]: p < 0.006). A threshold of GGT/5'-NU < 1.9 had a sensitivity of 40% and a specificity of 100% for the diagnosis of IHC. Although such hepatobiliary enzymes cannot be regarded as diagnostic, they can provide useful information to orientate the clinician in the diagnosis of cholestasis.