International co-validation of glycated hemoglobin A1c certified reference materials

Accurate quantification of glycated hemoglobin A1c (HbA1c) is essential for the diagnosis and glycemic control in diabetic patients. The validation of HbA1c certified reference material (CRM) enhances the accuracy and comparability of HbA1c measurements. An international co-validation of HbA1c CRMs was conducted among the National Institute of Metrology, P.R. China (NIM), the Korea Research Institute of Standards and Science (KRISS), and the National Metrology Institute of Japan (NMIJ). Candidate reference materials (RMs) of VHLTPE, glycated VHLTPE, and two levels of HbA1c were developed and supplied by NIM. NIM investigated the homogeneity and stability of these materials, finding no inhomogeneity and confirming stability throughout the co-validation period. Isotope dilution mass spectrometry was employed for the quantitation of both hexapeptides in solution and HbA1c in a matrix. All three national metrology institutes (NMIs) were involved in the quantification of hexapeptides in solution, whereas only NIM and KRISS were involved in the quantification of HbA1c in the matrix. E_n values for both hexapeptides and HbA1c in the matrix were calculated, all being less than 1, indicating good agreement with the certified values. The successful co-validation of these CRMs demonstrates the reliability of the certified values, thereby benefiting the accuracy and comparability of HbA1c measurements.