Hemoglobin A(1c): Past, present and future

Hemoglobin A(1c) (HbA(1c)) has been used for decades to monitor the control of glycemia in diabetes. Although HbA(1c) is currently undergoing a reassessment, and major developments have been underway in recent years, HbA(1c) is not recommended at present for diabetes screening or diagnosis. The objective of this review is to summarize the recent developments and to review a potential diagnostic role for HbA(1c). Implementation of changes in HbA(1c) results and units of measurements have been suggested for the purpose of test standardization. These include lower reference ranges (by about 1.5–2 points) and measurement units expressed in percentage (%), as mg/dL (mmol/L) or mmol/mol (or a combination of these units). In diabetes screening and diagnosis, the current diagnostic guidelines use measurement of plasma glucose either fasting or after glucose load. These diagnostic methods have shortcomings warranting a potential diagnostic role for HbA(1c). While recent developments in HbA(1c) methodologies are acknowledged, it is not yet known which changes will be implemented, and how soon. Given the recent literature supporting HbA(1c) diagnostic abilities, and given the shortcomings of the current guidelines, it is possible that a diagnostic role for HbA(1c) may be considered in future practice guidelines, globally. Very recently, the first of such recommendations has been proposed by an expert panel, as announced by the US Endocrine Society.