Best use of the recommended IFCC reference method, material and values in HbA_1C analyses

Abstract

The results of Finnish HbA_1C surveys (Labquality Ltd.) during the past 10 years have undergone continuous improvement with smaller overall coefficients of variation for the HbA_1C mean values of all methods (from 7.5 to 5.4% for normal and from 8.9 to 4.7% for diabetic samples). Most of the HbA_1C methods are certified for traceability to the Diabetes Control and Complication Trial (DCCT) designated comparison method, which originally was a high‐performance liquid chromatography (HPLC) method (Bio‐Rex 70, Bio‐Rad) but is no longer in routine use. It was therefore important that the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) had prepared both reference preparations and method for the determination of HbA_1C. However, the very demanding reference method is not realistic for use in clinical laboratories. According to the present study, the mean HbA_1C values of the Labquality Ltd. showed significant correlations to the HbA_1C values of The European Reference Laboratory for Glycohemoglobin (r = 0.999) and to the values using the IFCC method (r = 0.999). The reference values of the IFCC method (mainly those of the manufacturer) range from 2.85 to 3.81%, being significantly lower than the present DCCT values (4.0–6.1%). Since it may take some time before consumers are ready to accept the new IFCC reference values for general use, we propose that the IFCC reference materials and method should be used for calibration of the present methods to the well‐known DCCT levels.

• DCCT
• diabetes
• NGSP
• quality assurance
• treatment recommendations

Acknowledgements

We thank Dr. Cas Weykamp, Winterswijk, The Netherlands, for analyzing the HbA_1C values with the reference methods, and Labquality Ltd. for the results of the HbA_1C surveys placed at our disposal. We also thank laboratory technician Tero Hongisto for preparing the EDTA blood samples for the surveys, and the members of the Glycohemoglobin Working Group of Labquality Ltd. for fruitful discussions.