Abstract:

The International Federation of Clinical Chemistry and Laboratory Medicine（IFCC） introduces the reference methods on the determination of glycated hemoglobin A_1c（HbA_1c） and the laboratory network inter-comparison and value assignment. This article briefly introduces the principle and operation of reference methods and also includes the last international reference laboratory network inter-comparison as an example. A total of 6 calibrators,5 inter-comparison samples,2 controls and 3 CalCheck samples are used with glutamic acid endoproteinase to release glycated six peptides （Glu-Val-His-Leu-Thr-Pro-Glu） and non-glycated six peptides （Val-His-Leu-Thr-Pro-Glu）. High performance liquid chromatography（HPLC） is used to collect fraction of six peptides' mixture. The HbA1c and hemoglobin A₀（HbA0） mixture is separated by capillary electrophoresis. The peak areas of HbA_1c and HbA₀ are integrated,and the ratio is calculated. The calibration curve is made by measuring 5 calibrators. The linearity between test values and given values is good with the equation Y_{given values}= 0.998 36 Xtest values-0.000 08 （R2=0.999 82）. The test results show low proportional bias（-0.001） and systematic bias （0.23）when they are assessed with other network laboratories. IFCC reference method can accurately measure HbA_1c. In this inter-comparison,the results are qualified and thus can assign values accurately and reliably to IFCC calibrators. The values provide supports for global HbA_1c traceability to IFCC international units.

Key words: Glycated hemoglobin A1c, Reference method, The International Federation of Clinical Chemistry and Laboratory Medicine, Comparison