Correlation of glycosylated hemoglobin measured by affinity vs ion exchange chromatography with mean blood sugar in pediatric IDDM patients.

Affinity chromatography provides a more specific estimate of glycosylated hemoglobin (GlyHb) than does ion exchange chromatography (HbA1). However, whether GlyHb correlates closer than HbA1 with mean blood glucose has not been established. GlyHb and HbA1 were measured in pediatric IDDM patients attending a clinic (n = 285 visits) over a one year period and correlated with the mean of a patient's blood glucose measurements from records of home blood glucose monitoring. Mean GlyHb was higher than mean HbA1 (10.8% vs 9.6%) as was its standard deviation (2.2% vs 1.5%). While both GlyHb (r = 0.75) and HbA1 (r = 0.65) were strongly correlated with estimates of mean blood glucose, the correlation with GlyHb was significantly stronger than with HbA1 for the entire spectrum of metabolic control (P = 0.03), as well as for a segregated group of 'poorly controlled' patients with mean blood glucose greater than 150 mg/dl (P = 0.04). The results suggest that GlyHb is more accurate than HbA1 for estimating metabolic control and that GlyHb shows greater discriminating power than HbA1, especially at high concentrations of blood sugar. The mean blood glucose can be estimated from the equation: mean blood glucose (mg/dl) = (11.3 x GlyHb) + 32.