Immunonephelometric Carbohydrate-Deficient Transferrin Results and Transferrin Variants

To the Editor:Carbohydrate-deficient transferrin (CDT)1 is a biomarker of growing importance in the assessment of alcohol abuse after conviction for drunk driving. CDT is a more specific indicator for alcohol than traditional liver function tests and is used for identification and follow-up of chronic high alcohol consumption (1). Various methods have been introduced for assaying CDT in serum, including isoelectric focusing, ion-exchange chromatography, HPLC, capillary zone electrophoresis (CZE), and latex enhanced immunonephelometry (1, 2).Measuring the CDT percentage (%CDT) in a forensic context demands CZE or HPLC methodology, because it provides high-resolution separation of serum transferrin (Tf) isoforms and allows the detection of genetic variants and glycosylation disorders. In some cases, the interpretation of CDT results is hampered by the presence of mutant Tf (3). In addition to wild-type Tf (C), D variants (cathodal to C) and B variants (anodal to C) have been described (1). The allele frequencies of the Tf subtypes vary among populations of different ethnicities (4). Exact measurement of D variants of CDT is difficult, however, because di- and trisialylated Tf may coelute with the tetrasialylated D peak …