The 2007 Consensus Statement from the American Diabetes Association endorsed that Estimated Average Glucose (eAG) as the best way to predict A1C.

A1C, an abbreviated term used to indicate glycated hemoglobin testing, measures the amount of glucose attached to a protein called Hemoglobin. ADA standards consider A1C values less than 7% as a satisfactory control for people for diabetes. It was found in the 1970s, A1C fluctuated proportionately with fasting, postprandial and mean glucose over the past 8-12 weeks. Average Glucose (AG) was then proposed to define relationship with A1C, offering practical daily goals for patients with diabetes. Intensive treatment to achieve A1C goals are associated with decreased diabetes complications in patients with type 1 or type 2 diabetes.

The A1C-Derived Average Glucose (ADAG) study introduced the term eAG using continuous glucose monitoring (CGM) to examine the relationship between A1C and glucose. 507 participants wore CGM devices for at least 2 days and repeated 4 times to yield 25,000 glucose values of each participant. The study included 10 centers worldwide.

Although using eAG for reporting has yet to be standardized, the findings have been endorsed as the current best method correlating to lab A1C values.

SOURCE:
The Diabetes Educator, August 2009.
Diabetes Care August 2008 vol. 31 no. 8 1473-1478.