Haemoglobinopathies: a pitfall in the assessment of glycosylated haemoglobin by ion-exchange chromatography.

Total glycosylated haemoglobin was determined by a minicolumn ion-exchange chromatography technique (Bio-Rad) and correlated with the mean of fasting and post-prandial blood glucose values for the preceding 6 weeks. In 360 diabetic subjects, free of congenital haemoglobinopathies and other detected causes of haemoglobin A1 misinterpretation (reference diabetic group), a highly significant correlation was established between haemoglobin A1 and glucose (y = 0.54 X +4.91; r = 0.791; p less than 0.01). In 28 of the 29 patients with heterozygous haemoglobinopathies (HbS, C, D, E), the apparent haemoglobin A1 values were lower than expected according to the 95% confidence limits of the diabetic reference group. The apparent haemoglobin A1 value was above these limits in patient 29, with beta thalassaemia. Patients with inappropriate glycosylated haemoglobin values should be investigated for causes of haemoglobin A1 misinterpretation, in particular, haemoglobinopathies.