Are HbA1c or GHb assays superior in measuring glycemic control?

Updated: Jul 13, 2021
  • Author: Romesh Khardori, MD, PhD, FACP; Chief Editor: George T Griffing, MD  more...
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Glycated hemoglobin can be measured as HbA1c, HbA1 (HbA1a, b, and c), or total glycated hemoglobin (GHb). HbA1c constitutes approximately 80% of GHb.

Whether HbA1c or GHb assays are superior for measuring glycemic control is debatable. Hemoglobinopathies can affect both measurements. Because the Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospective Diabetes Study (UKPDS), as well as the ADA Standards of Care, use HbA1c measurements, this article refers to HbA1c as the standard for glycemic control.

Using GHb measurements is acceptable, but these values are 1-2% higher than HbA1c concentrations. When using GHb, a conversion factor to HbA1c for the assay utilized is helpful.

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