Longitudinal comparison of carbohydrate-deficient transferrin and gamma-glutamyl transferase: complementary markers of excessive alcohol consumption.

The utility of carbohydrate-deficient transferrin (CDT) and gamma-glutamyl transferase (GGT) as biochemical markers of excessive alcohol consumption was studied in alcohol-dependent subjects. Serum samples were collected once weekly from 10 male out-patients undergoing a 6-month alcohol treatment programme. Frequency of relapse into drinking (defined as any intake of alcoholic beverage) was assessed by self-reports during patient interviews three times per week and by daily determination of the 5-hydroxytryptophol level in urine. A marked decrease in mean CDT and GGT values was observed during the initial month. Only one patient remained totally abstinent throughout the observation period, while four had sporadic relapses (2-5 days with alcohol consumption). Both CDT and GGT remained below the respective reference limits in those patients. The other five patients drank more frequently (range 22-57 days) and increased their mean levels of CDT and GGT after the initial decrease. As determined from the values at admission and during the course of the study, CDT appeared to be the most sensitive marker in six out of the 10 patients. In one patient, both markers were affected in a parallel way, whereas two of those with frequent relapses responded to alcohol consumption with a marked increase in GGT, but with no or only a slight increase in CDT. One patient did not show any abnormal CDT or GGT values. In 54 female and 60 male serum samples collected at random from patients during admission at an alcohol detoxification unit, 35% and 58% of the CDT values exceeded the reference limits for females and males, respectively. For GGT, 59% of the female and 67% of the male values were above cut-off. Carbohydrate-deficient transferrin and GGT were not significantly correlated. Taken together, the present results indicate that measurement of both CDT and GGT will increase the possibility of identifying excessive alcohol consumption. By following changes in CDT and GGT values during a period of alcohol withdrawal, the most sensitive individual marker can be determined. This in turn allows for improved detection of relapse into heavy drinking during long-term monitoring of out-patients.