[The glycated hemoglobin: indication, interpretation and limitations].

HbA1c is defined by the slow and irreversible binding of glucose to the N-terminal valine of one or both of the beta chains of hemoglobin A (HbA). It is a marker that is becoming increasingly important because of its role in both the diagnosis and monitoring of diabetic patients with type 1 and type 2. It reflects glycemic control of two or three months. Learned societies such as the IFCC and NGSP contributed to its standardization, which allows inter-laboratory comparison of results. Its assay uses chromatographic, electrophoretic or immunochemical methods. The HbA1c concentration is expressed in percent and in mmol/mol, and a number that is between 4 and 6% (20 and 42mmol/mol) is desirable. However, HbA1c cannot be used in some cases and fructosamine assay must be considered.