Background
Serum gamma‐glutamyltransferase (GGT) activity is a sensitive but non‐specific marker of non‐alcoholic fatty liver disease (NAFLD). Recently, four GGT fractions (big‐, medium‐, small‐, free‐GGT) were described in humans.
Aim
We aimed to investigate whether a specific GGT fraction pattern is associated with NAFLD.
Methods
Gamma‐glutamyltransferase fractions were determined in patients with NAFLD (n = 90), and compared with those in control subjects (n = 70), and chronic hepatitis C (CHC, n = 45) age and gender matched.
Results
Total GGT was elevated in NAFLD as compared to controls (median, 25°–75°percentile: 39.4, 20.0–82.0 U/L vs. 18.4, 13.2–24.9 U/L respectively, P < 0.001). All fractions were higher in NAFLD than in controls (P < 0.001). The b‐GGT showed the highest diagnostic accuracy for NAFLD diagnosis [area under ROC curve (ROC‐AUC): 0.85; cut‐off 2.6 U/L, sensitivity 74%, specificity 81%].
Also subjects with CHC showed increased GGT (41.5, 21.9–84.5 U/L, P < 0.001 vs. controls, P = n.s. vs. NAFLD), as well as m‐, s‐, and f‐GGT, while b‐GGT did not show any significant increase (P = n.s. vs. HS, P < 0.001 vs. NAFLD). In subjects with CHC, s‐GGT showed the best diagnostic value (ROC‐AUC: 0.853; cut‐off 14.1 U/L, sensitivity 73%, specificity 90%). Serum GGT did not show any value in the differential diagnosis between NAFLD and CHC (ROC‐AUC 0.507, P = n.s.), while b‐GGT/s‐GGT ratio showed the highest diagnostic accuracy for distinguishing NAFLD and CHC (ROC‐AUC: 0.93; cut‐off value 0.16, sensitivity 82%, specificity 90%).
Conclusions
b‐GGT increases in NAFLD, but not in CHC. GGT fraction analysis might help in improving the sensitivity and specificity of the diagnosis of NAFLD and other liver dysfunctions.