Improved diagnostic classification of alcohol abusers by combining carbohydrate-deficient transferrin and γ-glutamyltransferase

Background: Biochemical markers can provide objective evidence of high alcohol consumption. However, currently available markers have limitations in their diagnostic performance. Methods: The diagnostic values of the most frequently used markers [carbohydrate-deficient transferrin (CDT), gamma -glutamyltransferase (GGT), aspartate aminotransferase, alanine aminotransferase, and mean corpuscular volume] were studied in an analysis of six different clinical studies (n = 1412) on alcohol abusers and social drinkers. The purpose of the analyses was to determine whether a combination of markers would improve the diagnosis of subjects. Results: Discrimination between alcohol abusers and social drinkers, as measured by the areas under nonparametric ROC plots, was significantly better (P <0.001) for the new combined marker [<gamma>-CDT = 0.8 In(GGT) + 1.3 In(CDT)] than for any of the separate markers or combination of CDT or GGT with other markers. The cutoff values for gamma -CDT (6.5) can be taken to be the same among males and females. Conclusions: The combined variable gamma -CDT is a powerful tool to discriminate alcohol abusers from social drinkers and is recommended for clinical use. (C) 2001 American Association for Clinical Chemistry.