VALIDATION BY ISOELECTRIC-FOCUSING OF THE ANION-EXCHANGE ISOTRANSFERRIN FRACTIONATION STEP INVOLVED IN DETERMINATION OF CARBOHYDRATE-DEFICIENT TRANSFERRIN BY THE CDTECT ASSAY

Serum concentration of carbohydrate-deficient transferrin (CDT) is use d for laboratory diagnosis of chronic alcohol abuse. Using isoelectric focusing for validation of the initial isotransferrin fractionation s tep involved in the determination of CDT by the CDTect assay, we found a complete in vitro iron saturation of transferrin and sufficient sta bility of the transferrin iron load during column passage; effective s eparation of non-CDT-isotransferrins and CDT-isotransferrins at the mi crocolumns; partial coelution of trisialo-Fe-2-transferrin, which did not significantly affect CDT measurement; partial retention of CDT-iso transferrins, especially disialo-Fe-2-transferrin, which may cause fal sely negative results for CDT at the upper reference limits; good prec ision of the isotransferrin fractionation step; and no significant eff ects of low concentrations of serum protein and transferrin. We strong ly urge standardization of CDT analysis and suggest isoelectric focusi ng for validation of CDT analysis methods and verification of odd resu lts.