Labile glycosylated hemoglobin contributes to hemoglobin A1 as measured by liquid chromatography or electrophoresis.

The utility of glycosylated hemoglobin (HbA1) measurement as an index of chronic control in diabetes can be adversely affected by interference from a labile glycosylated fraction that changes rapidly with acute changes in blood glucose concentration. I used a "high-pressure" liquid-chromatographic assay and a newly developed electrophoretic assay to quantitate the contribution of this labile fraction. If erythrocytes are incubated at 22 degrees C in isotonic saline for 12 h before hemolysis, the labile fraction is eliminated. Its contribution is similar as measured by both assays: 2-3.5% of total HbA1 in normal cells and 7-9.5% in diabetic cells. A 3-h incubation of erythrocytes with glucose produces acute changes in apparent HbA1 concentrations by both assays, but such changes can be eliminated by the incubation in saline. Although current methods are time consuming, the labile glycosylated hemoglobin must be removed when the sample is prepared for HbA1 measurement by liquid chromatography and electrophoresis if results are not to be factitiously high.