Comparison of HPLC and Capillary Electrophoresis for Confirmatory Testing of the Alcohol Misuse Marker Carbohydrate-Deficient Transferrin

Abstract

The major form of the iron-transport glycoprotein transferrin in blood contains 2 N-linked disialylated biantennary oligosaccharide chains (glycans) and is named tetrasialotransferrin. Regular high alcohol consumption (mean of at least 50–80 g/day) generally alters the glycosylation profile of transferrin (1), increasing the relative amounts of glycoforms lacking one (disialotransferrin) or both (asialotransferrin) N-glycans (2)(3). The alcohol-related glycoforms are collectively referred to as carbohydrate-deficient transferrin (CDT). CDT measurements are widely used for identifying individuals with alcohol problems in various medical settings (e.g., addiction treatment) and for monitoring abstinence from alcohol in outpatient treatment programs (e.g., when drunk-driving offenders reapply for a driver’s license) (4). When drinking is discontinued, the CDT concentration normalizes with a half-life of 1.5–2 weeks (5)(6). The main advantage of CDT over the conventional alcohol biomarkers, such as the liver function test γ-glutamyltransferase, is the higher specificity for alcohol misuse with resulting lower risk for false-positive identifications (7)(8). Since the discovery of CDT as an alcohol marker (1), a multitude of analytical techniques and methods have been applied for its measurement (1)(9). The most widely used assays worldwide today are the Axis-Shield %CDT immunoassay and various automated applications thereof, such as %CDT TIA from Bio-Rad and Tina-quant® %CDT from Roche (10)(11). These assays are based on ion-exchange minicolumn chromatographic isolation of the CDT fraction, separate measurement of CDT and total transferrin using the same transferrin antibody, and calculating CDT as a percentage of total transferrin (%CDT). Immunologic methods are convenient and time-efficient for routine use in central laboratories with high specimen throughput, but because these tests separate CDT from non-CDT moieties on the basis of differences in isoelectric point (pI), they will be disturbed by genetic transferrin polymorphisms (12) and by congenital disorders of glycosylation (13), which …