Glike Hemoglobin (HBA1C)
Synopsis
Diabetes is a chronic metabolic disorder in which carbohydrate, fat, and protein metabolism cannot be adequately utilized due to insulin deficiency or defects in insulin action. According to criteria by the American Diabetes Association (ADA) and the Turkish Society of Endocrinology and Metabolism (TEMD), an HbA1c value of ≥6.5% (≥48 mmol/mol) indicates overt diabetes, whereas values between 5.7% and 6.4% (39-47 mmol/mol) represent a high-risk group for diabetes. HbA1c is formed when plasma glucose non-enzymatically and irreversibly binds to the N-terminal region of the erythrocyte beta chain, forming a stable ketoamine structure via Amadori rearrangement. This parameter reflects the average plasma glucose concentration over the approximate 120-day lifespan of erythrocytes, correlating best with the glycemic status of the preceding 8-12 weeks. Techniques such as cation-exchange chromatography, boronate affinity, and immunoassay are used for measurement; although HPLC offers high analytical performance, it can be affected by high levels of triglycerides, urea, bilirubin, or conditions that shorten red blood cell lifespan. HbA1c should not be used as a diagnostic test in conditions altering the erythrocyte lifespan, such as pregnancy, recent bleeding or transfusion, hemodialysis, and erythropoietin therapy. Standardizing test results according to the IFCC reference system and reporting them in both % and mmol/mol units has been accepted globally.
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