[Analytical problems in determination of hemoglobin A1c and the different ways of its interpretation].Orv Hetil. 2009 Apr 19; 150(16):747-51.OH
Glycated proteins are formed during the nonenzymatic reaction of glucose and amino groups of proteins. Hemoglobin A1c is formed by the condensation of glucose with the N-terminal valine residue of each beta-chain of hemoglobin A. The amount of glycated hemoglobin in blood depends on both life-span of red blood cells and blood glucose concentration. As the rate of formation of hemoglobin A1c is directly proportional to the concentration of glucose in the blood, it represent the integrated values for glucose over the preceding 6 to 8 weeks. Hemoglobin A1c determination is widely used for monitoring long-term glycemic control, and it is a risk factor for complications of diabetes. The concentration of blood hemoglobin A1c depends on further factors such as half-life of hemoglobin, blood carbohydrates, blood analytes, methods of determination and calibration. Committees were established under the auspices of the American Association of Clinical Chemistry, American Diabetes Association, International Federation of Clinical Chemistry (IFCC) to standardize HbA1c assays (DCCT: Diabetes Control and Complications Trial, NGSP: National Glycohemoglobin Standardization Program, IFCC reference method for measurement of HbA1c). The NGSP recommends to report HbA1c result in % (g HbA1c/g hemoglobin) while IFCC suggests mmol HbA1c/mol hemoglobin A. Reports are presenting mathematical relationship between HbA1c and average glucose concentration in blood, however, the clinical usefulness of estimating average serum glucose from HbA1c level is under discussion.