Proteins may undergo glycosylation by enzymatic or nonenzymatic mechanism.1 Nonenzymatic glycosylation of proteins can occur under physiological conditions. Nonenzymatic glycosylation of hemoglobins (Hbs) results in the formation of Hb A1a, Hb A1b, and Hb A1c, which are collectively known as glycosylated hemoglobins. Hemoglobin A1c is the Amadori reaction product of the N-terminal valine of each β-chain of Hb A with glucose.2
Hemoglobin A1c has been extensively used as a measure of metabolic control in diabetic patients.1 The degree of control of hyperglycemia as evaluated by the concentration of Hb A1c in blood has been found to correlate with the occurrence of diabetic complications, particularly vasculopathy.3 Brancati,4 in an excellent, thought-provoking editorial in the April 10, 1995, issue of the Archives discussed many aspects of the benefits of tight glycemic control in diabetes mellitus. However, the role that Hb