Hemoglobin A1c (HbA1c)

Hemoglobin A1c values are used to assess glucose control in diabetes, and in 2010 the American Diabetes Associations affirmed the decision of an international expert committee recommendation to use the A1c test to diagnose diabetes with a threshold ≥6.5%. Point-of-care A1c assays are not sufficiently accurate at this time to use for diagnostic purposes.

Any cause of shortened erythrocyte survival will reduce exposure of erythrocytes to glucose with a consequent decrease in Hb A1c (%). Causes of shortened erythrocyte lifetime might be hemolytic anemia or other hemolytic diseases, homozygous sickle cell trait, pregnancy, or recent significant or chronic blood loss. Glycated Hb F (fetal hemoglobin) is not detected as it does not contain the glycated β chain that characterizes Hb A1c. Specimens containing high amounts of Hb F (>10%) may result in lower than expected Hb A1c.

Factors such as duration of diabetes, adherence to therapy, and age of patient should also be considered in assessing the degree of blood glucose control.

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