International clinical harmonization of glycated hemoglobin in Japan: From Japan Diabetes Society to National Glycohemoglobin Standardization Program values

In 1999, the Japan Diabetes Society (JDS) launched the previous version of the diagnostic criteria of diabetes mellitus, in which JDS took initiative in adopting glycated hemoglobin (HbA1c) as an adjunct to the diagnosis of diabetes. In contrast, in 2009 the International Expert Committee composed of the members of the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD) manifested the recommendation regarding the use of HbA1c in diagnosing diabetes mellitus as an alternative to glucose measurements based on the updated evidence showing that HbA1c has several advantages as a marker of chronic hyperglycemia. The JDS extensively evaluated the usefulness and feasibility of more extended use of HbA1c in the diagnosis of diabetes based on Japanese epidemiological data, and then the ‘Report of the Committee on the Classification and Diagnostic Criteria of Diabetes Mellitus’ was published in the Journal of Diabetes Investigation and Diabetology International. The new diagnostic criterion in Japan came into effect on 1 July 2010. According to the new version of the criteria, HbA1c (JDS) ‡6.1% is now considered to indicate a diabetic type, but the previous diagnosis criteria of high plasma glucose (PG) levels to diagnose diabetes mellitus also need to be confirmed. Those are as follows: (i) FPG ‡126 mg ⁄dL (7.0 mmol ⁄L); (ii) 2-h PG ‡200 mg ⁄dL (11.1 mmol ⁄L) during an oral glucose tolerance test; or (iii) casual PG ‡200 mg ⁄dL (11.1 mmol ⁄L). If both PG criteria and HbA1c in patients have met the diabetic type, those patients are immediately diagnosed to have diabetes mellitus. In the report, the HbA1c measurements in Japan are well calibrated with JapaneseClinical-Laboratory-Use Certified Reference Material (JCCRM). The certified values are determined by a high-resolution type ion-exchange high performance liquid chromatography (HPLC) (KO 500 method) and certified using the designated comparison method (DCM) of the Japan Society of Clinical Chemistry (JSCC) and the JDS. After incorporating a proportional bias correction to the value anchored to the peptide mapping method of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), the DCM actually measures b-N-monodeoxyfructosyl hemoglobin and has an intercept approximately equal to zero against the peptide mapping method of IFCC inmeasuring fresh raw human blood samples. Furthermore, standardization of HbA1c in Japan was initiated in 1993, and the serial reference materials from JDS Lot 1 to JDS Lot 4 are well certified using the DCMuntil now. In the new diagnosis criteria, the new cut-point of HbA1c (JDS) for diagnosis of diabetes mellitus is 6.1%, which is equivalent to the internationallyused HbA1c (National Glycohemoglobin Standardization Program [NGSP]) 6.5%, as HbA1c (NGSP)(%) is reported to be equivalent to 1.019 · HbA1c (JDS)% +