Hemoglobin A1c and the Estimated Average Glucose

Hemoglobin Variants

July 2009

In the United States, hemoglobin S is the most common variant, followed by hemoglobin C, then hemoglobin E, and hemoglobin D (Punjab/Los Angeles).  Worldwide, hemoglobin variants follow this similar trend except hemoglobin E is more common than hemoglobin C.  Many, but not all, HbA1c methods are unaffected by the presence of some or all of these variants.  For patients who have no hemoglobin A, such as homozygous S or C patients, hemoglobin A1c measurement will be inaccurate and it is recommended that an alternate form of glycemia be used such as fructosamine.  In these patients a shortened red blood cell lifespan is typically encountered, which leads to a falsely low hemoglobin A1c.

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Hemoglobin Variants

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Jump to section:

• Introduction
• US Diabetes Prevalence
• Diagnosis of Diabetes
• Categories of Glucose Values
• Importance of Diagnosis
• Role of the Laboratory
• Fasting Plasma Glucose
• Fasting Plasma Glucose
• Hemoglobin A1c (HbA1c)
• Glycation
• HbA1c Concentration
• Diabetes Treatment Goals
• HbA1c Methods
• Hemoglobin Variants
• Hemoglobinopathies
• Reporting HbA1c as an eAG
• HbA1c and Average Glucose
• Derivation of Estimated Average Glucose (eAG)
• HbA1c/eAG Table
• Limitations
• Endorsement of eAG
• HbA1c for Diagnosis of Diabetes
• Disadvantages
• International Expert Committee Report on the Role of the A1c Assay in the Diagnosis of Diabetes
• HbA1c at Mayo Clinic
• Conclusions
• Questions?