To explore the clinical application of the detection of serum alkaline phosphatase (ALP), gamma glutamyl transpeptidase (GGT) and ALP/upper limit of normal (ULN) divided by GGT/ULN (ALP^×/GGT^×) in the differential diagnosis of the cholestatic liver disease.

Twenty patients with drug-induced cholestatic patients (drug-induced cholestatic liver disease group), 50 cases with primary biliary cholangitis [primary biliary cholangitis group(PBC)] and 55 cases with choledocholithiasis (choledocholithiasis group) were enrolled from January 2012 to July 2016, according to the diagnostic criterias respectively.ALP and GGT were examined by rate method.To compare mean differences of above makers and draw their ROC curves among groups.

There were no significant differences of ALP among groups (F=0.27, P>0.05). The differences of GGT among groups were significant (F=9.44, P<0.05). However, there was no significant difference between drug-induced cholestatic liver disease group and PBC group (q=2.52, P>0.05). The level of GGT of choledocholithiasis group [(424.7±317.0)U/L] was higher than those of drug-induced cholestatic liver disease group [(152.2±51.0)U/L] and PBC group [(230.5±121.0)U/L], the differences were significant (q=10.2, 8.3; P<0.05). The differences of ALP^×/GGT^× among groups were statistically significant(F=8.23, P<0.05). The level of ALP^×/GGT^× of drug-induced cholestatic liver disease group (0.95±0.54) was higher than those of PBC group (0.64±0.33)and choledocholithiasis group (0.37±0.18), and the ALP^×/GGT^× of PBC group was higher than that of choledocholithiasis group, these differences were statistically significant (q=4.2, 6.4, 5.6; P<0.05). The areas of ALP, GGT and ALP^×/GGT^× under the receiver operating characteristic (ROC) curves in the differential diagnosis between drug-induced cholestatic liver disease group(+ ) and choledocholithiasis group(-) were 0.552, 0.189, 0.972, those were 0.498, 0.298, 0.749 between PBC group (+ ) and choledocholithiasis group(-), those were 0.645, 0.319, 0.741 between drug-induced cholestatic liver disease group(+ ) and PBC group(-). The areas of ALP^×/GGT^× were the largest.The sensitivity and specificity of ALP^×/GGT^× were superior to those of ALP and GGT, which were 90.9% and 62.0%, 100.0% and 84.6%, 100.0% and 38.5%, respectively in the differential diagnosis of drug-induced cholestasis group and PBC group, drug-induced cholestasis group and choledocholithiasis group, PBC group and choledocholithiasis group.

ALP^×/GGT^× may be expected to become a new marker for differential diagnosis of cholestatic liver disease.ALP^×/GGT^× makes up for the insufficient application of serum ALP and GGT, which is important to differential diagnosis of drug-induced cholestasis, PBC and choledocholithiasis.