[Identification of elevated carbohydrate-deficient transferrin (CDT) serum level as transferrin (Tf)-D-variant by means of isoelectric focusing].

Many studies have shown carbohydrate-deficient transferrin (CDT) to be a sensitive and specific marker of chronic alcohol abuse. We present the case of a 23-year-old, healthy professional soccer player who caused a car accident due to alcohol consumption. Several CDT test results were elevated above the laboratory reference range and were considered to be caused by alcohol intake at a level commensurate with misuse and thus license reapplication was refused. In addition, assuming chronic alcohol abuse, the young man suffered from increasing social isolation. He was finally referred to our out-patient clinic for further evaluation on the assumption of a liver disease. Since chronic alcohol consumption was denied, and there was no evidence of liver disease, a qualitative characterization of the transferrin isoforms was performed. Isoelectric focusing of serum transferrin revealed a pattern atypical for chronic alcohol intake but detected a genetically determined transferrin (Tf)-D-variant. The changed amino acid sequence caused an overlapping of transferrin isoforms with different degrees of sialylation, thus revealing false-positive serum CDT values. Determination of this Tf-D-variant heterozygosity resulted in his social rehabilitation and license reinstatement. Thus, where the evidence for alcohol dependency is either uncertain or uncorroborated, qualitative isoelectric focusing of transferrin is a useful method for analyzing unexplained CDT elevations, thus increasing the value of CDT as a marker for chronic alcoholic abuse.