Gamma-glutamyltransferase in alcohol use disorders: Modification of decision limits in relation to treatment goals?

Serum gamma-glutamyltransferase (GGT) is recommended as a marker for alcohol use disorders by the Swedish National Guidelines for Addiction, although it has a low sensitivity and specificity. GGT is inexpensive and easily accessible but additional knowledge is required on how to use the marker in patients with various levels of alcohol intake. Levels of GGT were obtained from 37 male social drinkers (< 100 grams pure alcohol weekly) and 18 former alcohol-dependent males with long-term (6 +/- 5 years) abstinence. Reproducibility was calculated through repeated blood samplings. Mean serum activity of GGT, in former alcohol-dependent males, was 0.26 microkat/L with an intra-class correlation coefficient of 0.85. In social drinkers, these figures were 0.34 microkat/L and 0.92, respectively. In treatment of males, with the goal of abstinence, upper reference limit is suggested to be 0.40 microkat/L. Goals of non-harmful drinking (< 100 grams weekly) suggest higher limits (0.62 microkat/L). Thirty percent increase of GGT should be suggestive of relapse.