Abstract
Introduction: Glycated hemoglobin (HbA1c) is formed by non-enzymatic binding of glucose to the free amino group of the N-terminal end of the ß-chain of hemoglobin A. HbA1c is representative of the mean blood glucose level over three months. The aim of the study was to evaluate the Hemoglobin A1c immunoturbidimetric assay performance on two different commercial systems.Methods: We evaluated the precision and trueness for determination of HbA1c in whole blood. Concentrations of total hemoglobin and HbA1c were evaluated on Dimension Xpand (Siemens) and Cobas 501 (Roche) analyzers. HbA1c was measured in a latex agglutination inhibition test. Commercial controls Liquichek Diabetes Control Level 1 and Liquichek Diabetes Control Level 2 (Bio Rad) at two levels were used for quality control. Analytical validation of HbA1c included: within-run imprecision, between-day imprecision, inaccuracy and comparison determination on the human samples on 2 systems: Dimension Xpand and Cobas 501 analyzers. Results: Within-run imprecision on the commercially controls for Level 1 is 4.5% and Level 2 is 3.2% between-day imprecision on commercially controls is 6.1% Level 1 and 5.1% Level 2 for respectively inac- curacy on commercially controls for Level 1 is 1.8% and Level 2 is 4.8%. Method comparison on human samples shows the correlation coefficient of 0.99.Conclusion: The presented results of the analytical evaluation methods for the determination of HbA1c showed an acceptable accuracy and precision.
Highlights
Glycated hemoglobin (HbA1c) is formed by non-enzymatic binding of glucose to the free amino group of the N-terminal end of the ß-chain of hemoglobin A
A long time has passed since the discovery of HbA1c and its introduction in the laboratory practice related to the management of diabetes mellitus
Measurement of the total hemoglobin is based on a modification of the alkaline hematin reaction while the HbA1c measurement is based on turbidimetric inhibition immunoassay (TINIA)
Summary
Glycated hemoglobin (HbA1c) is formed by non-enzymatic binding of glucose to the free amino group of the N-terminal end of the ß-chain of hemoglobin A. The human erythrocyte is freely permeable to glucose, which can combine in non-enzymatic manner with hemoglobin to form HbA1c This non-enzymatic reaction between the alpha-amino group of the N-terminal valine of the hemoglobin beta-chain and glucose takes place to form an unstable aldimine of Schiff base intermediate. This reaction is slow and occurs at a rate that is proportional to the glucose concentration in the blood (1). They can be divided into two groups: the first group of HbA1c methods quantify glycated and non-glycated components (cation-exchange chromatography, agar gel electrophoresis); and the second group of HbA1c methods which separate glycated and non-glycated components based on structural differences (affinity chromatography and immunoassay) Most of these methods measure HbA1c, while other methods quantify total glycated hemoglobin (2). Laboratory results may differ depending on the analytical technique, the age of the subject and biological variation among individuals (3)
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