Quantification of carbohydrate-deficient transferrin by ion-exchange chromatography with an enzymatically prepared calibrator.

The current HPLC method for the determination of carbohydrate-deficient transferrin (CDT) yields ratios of CDT isoforms in relation to total transferrin, whereas the use of absolute concentrations obtainable in routine analysis by RIA and the reference ranges based here-upon is more convenient. We describe a modified HPLC method that likewise gives absolute CDT concentrations by using a calibrator prepared by treatment of transferrin with neuraminidase. Separation of isoforms could be improved and analysis time reduced to approximately 2 h. Iron saturation proved stable during chromatography. In contrast to a commercial RIA, the cheaper and more time-saving HPLC method excludes erroneous results caused by aged samples or genetic transferrin variants and enables the determination of asialo- and disialotransferrin. Both methods showed comparable precision and correlated with each other (y = 1.76 + 0.27x; Sy[symbol: see text]x = 5.38); for the HPLC method precision was 1.3-9.8% (within assay) and 6.2-10.6% (between assay). The clinical evaluation with a cutoff concentration of 80 mg/L resulted in a diagnostic specificity of 100% and a sensitivity of 82.5%.