The globalization of glycohemoglobin measurement for monitoring and for diagnosis of diabetes mellitus. Are we there yet?

Several milestones have been achieved since the discovery of HbA1c. These include identification of and agreement on a reference material that can be used as calibrant, development of a reference methodology, and improvement in between-laboratories performance and precision. There is now a clear definition of the HbA1c reference material (β-N-(1-deoxy)-fructosyl-hemoglobin). Reference methodologies have been developed and accepted as reference methods. The International Network of Reference Laboratories is already in place. A number of issues remain to be resolved, including reporting units for HbA1c and introduction of new target values. Comparison studies with International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) methodologies revealed that IFCC reference methodology, although the slope is invariably one that implies a stable relationship between IFCC reference methodologies and National Glycohemoglobin Standardization Program certified methods, the intercept is 0.88 to 2.15, suggesting that the IFCC reference method is lower. Several studies are now being conducted to establish the relationship between HbA1c and mean blood glucose levels. This may prove to be an acceptable method for reporting HbA1c. If this proves to be successful, globalization of HbA1c measurement can truly be achieved.