Evaluation of hemoglobin A2 quantitation assay and hemoglobin variant screening by capillary electrophoresis

To critically assess the method of capillary electrophoresis, we examined 97 clinical samples submitted for hemoglobin electrophoresis by both conventional methods (electrophoresis on cellulose acetate and citrate agar for detection of abnormal variants, ion-exchange chromatography for quantification of HbA2, alkali denaturation for quantification of HbF, supravital stains for detection of HbH) and CE. CE was performed using a 72 cm (50 cm to detector) x 50 microns i.d. fused-silica capillary with detection of absorbance at 200 nm. Of the 97 samples examined, 34 contained a hemoglobin variant. Migration time, the difference of the variant peak to that of HbA, was used in an attempt to identify the hemoglobin variant by CE. We found the method to be suitable for the quantification of HbA2, useful as a screening technique for the presence of hemoglobin variants, but unsuitable for the quantification of HbF.