title: Accuracy of b-GGT fraction for the diagnosis of non-alcoholic fatty liver disease.
abstract: 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.
  
  
  OBJECTIVE
  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.
authors.affiliation: Scuola Superiore Sant'Anna, Pz. Martiri della Libertà 33, Pisa, Italy. m.franzini@sssup.it
authors.forename: Maria
authors.initials: M
authors.lastname: Franzini
authors.forename: Irene
authors.initials: I
authors.lastname: Fornaciari
authors.forename: Vanna
authors.initials: V
authors.lastname: Fierabracci
authors.forename: Hassan Aziz
authors.initials: HA
authors.lastname: Elawadi
authors.forename: Valeria
authors.initials: V
authors.lastname: Bolognesi
authors.forename: Simona
authors.initials: S
authors.lastname: Maltinti
authors.forename: Angelo
authors.initials: A
authors.lastname: Ricchiuti
authors.forename: Nicola
authors.initials: N
authors.lastname: De Bortoli
authors.forename: Santino
authors.initials: S
authors.lastname: Marchi
authors.forename: Alfonso
authors.initials: A
authors.lastname: Pompella
authors.forename: Claudio
authors.initials: C
authors.lastname: Passino
authors.forename: Michele
authors.initials: M
authors.lastname: Emdin
authors.forename: Aldo
authors.initials: A
authors.lastname: Paolicchi
mesh_terms: D000368:Aged; D000410:Alanine Transaminase / Q000097:blood; D001219:Aspartate Aminotransferases / Q000097:blood; D016022:Case-Control Studies; D005234:Fatty Liver / Q000097:blood / Q000175:diagnosis*; D005260:Female; D019698:Hepatitis C, Chronic / Q000097:blood*; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease; D011237:Predictive Value of Tests; D012372:ROC Curve; D005723:gamma-Glutamyltransferase / Q000097:blood*
chemical_list: D005723:gamma-Glutamyltransferase; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase