Background: Four fractions of gamma-glutamyltransferase (GGT) with different molecular weight (b-, m-, s-, and f-GGT) are present in human plasma. Differential GGT fraction pattern is found in non-alcoholic liver disease (NAFLD) and chronic viral hepatitis, characterized by normal or decreased b-GGT/s-GGT (b/s) ratio, respectively.
Methods: Chromatographic fractional GGT analysis was performed on plasma obtained from 51 subjects: 27 alcoholics (mean (SD), age 45 (9) years; 23 males; 14 positive for viral infection), 24 abstinents from at least 1 month (43 (12) years; 20 males; 6 positive for viral infection). Twenty-seven blood donors matched for age and gender (44 (9) years; 23 males) were selected as controls.
Results: All fractions were significantly increased in alcoholics (P<0.001), s-GGT showing the largest increase, while only m-GGT and s-GGT were elevated in abstainers (P<0.01), in comparison with controls. The b/s ratio was significantly lower in both alcoholics and abstainers than in controls (median (25th-75th perc.): 0.10 (0.07-0.15), 0.16 (0.10-0.24), 0.35 (0.29-0.53), respectively, P<0.001). Viral infection did not significantly changes absolute values of individual GGT fractions in alcoholics, but the b/s ratio was significantly lower in virus positive than in virus negative subjects (0.08 (0.05-0.12), 0.14 (0.09-0.20), respectively, P<0.01).
Conclusions: The fraction pattern analysis might increase the specificity of GGT as biomarker of alcohol abuse, especially concerning the differential diagnosis between alcoholism and NAFLD, a common cause of elevated GGT level in the general population.
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