Electrophoretically determined haemoglobin A1 concentrations during short-term changes in glucose concentration.

In our experience, electrophoresis on agar gel is a very satisfactory alternative to the more widely used chromatographic methods for the determination of haemoglobin A1 (HbA1). Like the chromatographic method, the electrophoretic method is unable to detect any difference between the labile intermediate form of HbA1, which changes rapidly with acute changes in blood glucose level, and the more stable end-product, which reflects long-term glucose levels. In vitro at 37 degrees C the electrophoretically determined HbA1 concentration increases with increasing glucose concentration and with time in both normal and diabetic erythrocytes, but decreases to the preincubation concentration during further incubation of the erythrocytes in a glucose-free medium at 37 degrees C. Similarly, if normal or diabetic erythrocytes are incubated with isotonic saline before the HbA1 assay, the labile fraction is eliminated. In diabetics, the decrease in HbA1 concentration correlates with both the blood glucose level and the preincubation HbA1 concentration. Thus for HbA1 to be an accurate indicator of long-term glucose control in diabetic patients saline incubation of the erythrocytes may be necessary before HbA1 assay by the electrophoretic method, otherwise the assay results will also reflect recent changes in the blood glucose level.