Analysis of short-term changes in reversibly and irreversibly glycosylated haemoglobin AI: relevance to diabetes mellitus.

We have determined the stable (irreversibly glycosylated) fraction of haemoglobin AI (HbAI) on Bio-Rex 70 after incubation of red blood cells in 0.9 % saline solution for 6 h at 37 degrees C. The total (reversibly + irreversibly glycosylated fractions) HbAI was determined before each incubation. Labile (reversibly glycosylated) HbAI represented the difference between total and stable HbAI fractions. Total and stable HbAI fractions were determined during insulin- or meal-induced blood glucose fluctuations in 24 insulin-dependent diabetics and in seven subjects with impaired glucose tolerance. In the diabetics, the maximal fluctuation of total HbAI was 1.47% over 2-12 h, while the simultaneous plasma glucose variation was 21.5 mmol/l. The stable HbAI fraction did not change significantly. In diabetics the differences between the maximal and minimal values of plasma glucose and total HbAI were significantly correlated. Plasma glucose correlated with simultaneously determined total and labile HbAI fractions, but not with stable HbAI. In subjects with impaired glucose tolerance, similar changes in total but not in stable HbAI were observed during an oral glucose tolerance test. We conclude that, although rapid changes in chromatographically determined HbAI are relatively small, the determination of stable HbAI should be performed to circumvent this problem and to ensure a more accurate index of blood glucose control.