[New methods for the determination of transferrin isoforms in the diagnostics of alcohol abuse]

The new biochemical marker of chronic alcohol abuse are transferrin isoforms with a reduced number of sialic acids (asialo-, monosialo-, and disialotransferrin) called carbohydrate-deficient transferrins (CDTs). The usefulness of this indicator in the diagnostics of alcohol abuse has clearly been confirmed during the last years. The sensitivity and specificity of the CDT method as a marker of chronic alcohol abuse are higher than those found in commonly used tests. In routine analysis, CDTs have been assayed in the laboratories for ten years. Current CDT techniques allow for the determination of total CDT concentration (the absolute and/or relative amount) and provide the possibility of assaying its isoforms. In this paper the molecular structure of transferrin and different methods of CDT analysis are shown, with particular attention given to commercial tests. Analytical specificity and method-dependent (electrophoretic and chromatographic) reference values or cut-offs for serum CDT concentrations indicating chronic alcohol abuse are given in a table. Electrophoretic methods are characterized by higher selectivity (genetic variants) and higher sensitivity than chromatographic techniques. Isoelectric focusing, capillary electrophoresis, and high-performance liquid chromatography are used as the reference methods. Commercial procedures are based on transferrin saturation with iron followed by fractionation of protein (separating CDTs from non-CDT forms) by ion-exchange chromatography using microcolumns and a quantitative determination of CDT isoforms by immunological methods (radioimmunoassay, enzyme immunoassay, and turbidimetric immunoassay). Due to the different existing analytical methods, further standardization of CDT analysis and a redefinition of CDTs are necessary.