Capillary zone electrophoresis with a dynamic double coating for analysis of carbohydrate-deficient transferrin in human serum: impact of resolution between disialo- and trisialotransferrin on reference limits

Capillary electrophoresis with a dynamic double coating formed by charged polymeric reagents represents a very effective tool for the separation of iron-saturated transferrin (Tf) isoforms and thus the determination of carbohydrate-deficient transferrin (CDT) in human serum. The resolution between di- and trisialo-Tf is dependent on the applied voltage and capillary temperature. With a 50 microm inside diameter (ID) capillary of about 60 cm total length mounted into the P/ACE MDQ, 28 kV and 40 degrees C, the resolution of the two Tf isoforms is shown to be between 1.0 and 1.4, whereas with reduced voltage and/or temperature, increased resolution at the expense of elongated run times is observed. Best data with complete resolution (Rs > or = 1.4) are obtained at 20 kV and 30 degrees C. For the determination of CDT in serum, incomplete separation of di- and trisialo-Tf is demonstrated to have an impact on the reference limits. Analysis of the sera of 54 healthy individuals with no or moderate alcohol consumption and using valley-to-valley peak integration, the upper (lower) reference limits for CDT in relation to total Tf at the two power levels are 1.33 (0.52) and 1.57 (0.81)%, respectively, representing intervals that are significantly different (P < 0.001). Furthermore, the reference intervals are shown to be strongly dependent on the peak integration approach used. Valley-to-valley peak integration should only be employed for conditions with complete resolution between disialo- and trisialo-Tf.