Use of Carbohydrate-Deficient Transferrin (CDT) and a Combination of GGT and CDT (GGT-CDT) to Assess Heavy Alcohol Consumption in Traffic Medicine

Aims: Carbohydrate-deficient transferrin (CDT) has become widely used in traffic medicine to detect chronic alcohol abuse among subjects applying for driving-license renewal or regranting. By defining cut-off values in a large population of abstainers and moderate drinkers, we report on CDT, GGT-CDT (a combination of gamma-glutamylaminotransferase (GGT) and CDT) and the association between blood alcohol concentration (BAC) and CDT among Italian drivers. Methods: CDT was evaluated by a high performance liquid chromatography (HPLC)-based commercial kit in 652 abstainers or moderate drinkers, 603 drivers applying for driving-license regranting after a rehabilitation programme and 105 drivers involved in car accidents with blood alcohol concentration higher than the legal limit used in Italy (BAC > 0.5g/l). GGT-CDT was calculated according to Sillanaukee and Olsson and Niemela. BAC has been assessed by gas chromatography-mass spectrometry. Results: A common CDT cut-off (1.8%) and gender-specific GGT-CDT cut-off (4.15% for males, 3.56% for females) were calculated as 99.9th percentiles of the control population. Also, 3% and 27% of subjects were classified as CDT positive respectively among drivers applying for license regranting and drivers involved in car accidents. A significant association between BAC and both CDT values and CDT positivity was found, with a frequency up to 49% of CDT samples, suggesting chronic alcohol abuse, among drivers with BAC > 2.5g/l. Concordance between CDT and GGT-CDT was only moderate (kappa = 0.44), with CDT performing better than GGT-CDT. Conclusions: A relevant proportion of drivers with high BAC are chronic abusers. GGT-CDT, previously validated with CDT immunoassays, should not be applied to traffic medicine in its current form and its performances re-evaluated with CDT measured by HPLC.