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Dr. Bill's Commentaries

Egads - the eAG   (September 30, 2008)

Everyone who's had diabetes for a while is aware that there's some sort of relationship between their blood glucose (BG) levels and the results of their hemoglobin A1c (A1C) test. If someone's BGs are completely normal for the last three months, it's probably safe to assume that the A1C, if measured today, would be normal. But the reverse is not true: a normal A1C doesn't mean all the BGs the past three months have been normal: that might have been the case, but it's also possible, and indeed likely, that the BGs were a mixed bag, some high, some low, and some normal. For whatever it's worth, the A1C has become the "gold standard" lab test for measuring diabetes control: the lower the better; the usual advice is to aim to get your number under 7 (per one organization's recommendation) or 6.5 (per the recommendations of some other organizations).

A recent publication (Translating the A1C Assay Into Estimated Average Glucose Values) examined the relationship of the A1C assay and a more recent concept, the "estimated average glucose" (eAG). Researchers looked at BG and A1C results from 507 people (including 268 patients with type 1 diabetes, 159 with type 2, and 80 without diabetes). They looked at A1C levels compared to "at least 2 days of continuous glucose monitoring performed four times, with seven-point daily self-monitoring of fingerstick glucose performed at least 3 days per week." Approximately 2,700 glucose values were obtained from each participant during three months! Looking through all these results, they developed a mathematical formula, AG (in mg/dl)  = 28.7 x A1C - 46.7, to show the relationship between A1C and BG. Don't bother to memorize the formula: an interactive A1C / eAG calculator, is available [as of February 2012, moved at the ADA website at Estimated Average Glucose (eAG) ] , where they also have other materials regarding eAG.

In light of the study results, the American Diabetes Association (ADA) is recommending the use of eAG: pointing out that physicians can report now A1C results to patients using the same units (mg/dl or mmol/l) that patients see routinely in blood glucose measurements. The ADA states "Using eAG may help facilitate a better understanding of actual daily control - helping you and your health care provider to make necessary changes to your diet and physical activity to improve overall diabetes management." And in an accompanying editorial, it's said that "for those interested in adding another strategy to improve outcomes, we now have a new term that will likely be easier to explain to patients and to convey more meaning and importance to glucose control."

My take on the eAG? I think it's one more way for patients and physicians to get confused about how to measure diabetes control. After over 20 years of explaining the A1C concept to PWD, and getting at least a general understanding of the idea, now the "experts" want us to use another acronym that's just as hard to explain. And despite pronouncements that the eAG "will likely be easier to explain to patients" and "may help facilitate a better understanding", I'm unaware that anyone has done any studies to support these claims.

I'll bet that the eAG concept disappears within a year. Wanna bet?

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Dr. Bill Quick began writing at HealthCentral's diabetes website in November, 2006. These essays are reproduced at D-is-for-Diabetes with the permission of HealthCentral.

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