HbA1c: how do we measure it and what does it mean?

Purpose of review Description of recent developments in the standardization of HbA(1c) measurement and interpretation of HbA(1c) results. Recent findings HbA(1c) is extensively used in the management of patients with diabetes. The two major schemes to standardize HbA(1c) produce values that differ substantially. A prospective, multinational study revealed a linear correlation between HbA(1c) and average blood glucose. Some, but not all, assay methods are able to accurately measure HbA(1c) in individuals with common hemoglobin variants. Summary Progress in standardization of methods for HbA(1c) measurement has significantly reduced variation among different methods. The improved accuracy could allow HbA(1c) to be used for screening and diagnosis of diabetes. A consensus document recommends that HbA(1c) be reported in both NGSP (%) and IFCC (mmol/mol) units. HbA(1c) results can be translated into estimated average glucose (eAG), which could be reported in addition to HbA(1c).