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Jun 20, 2008

What's Your eAG? You'll Know Soon…

Tara Dairman

If you've ever wondered how your HbA1c level relates to the numbers you get on your blood glucose meter, help may be on the way. A recent study has found a more accurate way to "translate" HbA1c results into average blood glucose levels. In the near future, therefore, doctors and labs may be reporting HbA1c test results both as a percentage (the old way) and as an "estimated average glucose" (or eAG) number.

The HbA1c test, which is a measure of blood glucose control over the previous 2-3 months, measures how much glucose is bound to hemoglobin in the blood. It is expressed as the percent of hemoglobin molecules that have glucose attached. Typically, people who do not have diabetes have an HbA1c value of less than 6%; the American Diabetes Association (ADA) recommends an HbA1c goal of less than 7% for people with diabetes in general and lower goals for some individuals.

Now, the "International A1C-Derived Average Glucose" (ADAG) study has found a simple mathematical formula that can "translate" HbA1c levels into an eAG level expressed in milligrams per deciliter (mg/dl), the same units that people use when they monitor their blood glucose at home. (It can also translate HbA1c into an eAG in millimoles per liter [mmol/l], the unit commonly used outside of the United States.) The study was presented on June 7 at the American Diabetes Association's Scientific Sessions; it has been published online in Diabetes Care and will appear in print in the August issue of the journal.

The study took place in 10 centers and enrolled around 500 volunteers of various races and ethnicities. The volunteers consisted of 268 people with Type 1 diabetes, 152 people with Type 2 diabetes, and 80 people without diabetes. The researchers used a combination of continuous glucose monitoring and frequent blood glucose monitoring (seven times per day) to measure people's average glucose levels; they also checked their HbA1c levels in a central laboratory for three months.

By comparing these results, the researchers were able to develop a mathematical equation that accurately converted HbA1c levels into average glucose levels. They found the calculation to be about 84% accurate in all the different subgroups studied. The researchers point out, however, that people of African and Asian descent were underrepresented in the study, and that some groups of people—children, pregnant women, people with red blood cell disorders, and people whose diabetes was not in stable control—were not included in the study.

Why is this new number necessary? The researchers believe that an average glucose level in the units that people already use for self-monitoring will be easier to understand and will make it easier for people and their doctors see how to adjust their treatment.

It may take a year or more before eAG values start to show up alongside HbA1c values on lab reports across the country; this is because new software will need to be disseminated and loaded into lab machines. In the meantime, though, there are a few ways that you or your doctor can convert your HbA1c level into an eAG value now:

Go to www.diabetes.org/ag. There, you will find an online calculator that can convert HbA1c values into eAG values in mg/dl or mmol/l and vice versa; you'll also find a chart equating HbA1c values between 6 and 10 with eAG values.

Plug your HbA1c into the formula yourself:

28.7 x HbA1c - 46.7 = eAG (in mg/dl)

The ADA is also starting to provide handheld calculators to doctors that will allow them to calculate eAG values easily in the office.

Will eAG replace HbA1c down the road? The researchers who conducted this study think that it may. However, the eAG is just a new way of interpreting the same information provided by the HbA1c, and HbA1c values will still be reported by labs for the foreseeable future.

For more information about interpreting your HbA1c level, see the article "H-B-A-1-C (What It Is and Why It Matters)."

POST A COMMENT E-MAIL A FRIEND

Why is so much money being spent. If you can convert from A1C to eAC it isn't anything new. If I take my last A1C of 5.5 x 27.8 - 46.7 = 106.2. If I look at the old conversion chart 5.5 = 105. I don't see that we are gaining anything. LOWER is BETTER

Posted by: s6954118 | Jun 20, 2008 03:44 PM

Looks like there's a typo in your formula. The ADA site says '28.7 X A1C - 46.7 = eAG', not 27.8.

Posted by: David | Jun 20, 2008 05:26 PM

Invalid Study

To do any study about diabetes with only 500 people is pure folly, considering the number of diabetics out there! Furthermore, out of that number, only 268 had Type 1 diabetes. This represents too small a number to be of any statistical significance.

It is my sincere hope that people with diabetes will write to the ADA and to their doctors with requests not to use the results of this foolhardy study.

This is also not new or revolutionary. Other mathematical formulas, with slightly different results, have been around for more than six years. As this study has only an 84% rate of accuracy, that is too much for me. And, it doesn't take into account those people who have both very high and very low Blood Glucose numbers. An "average" by itself, is meaningless. Also, most doctors, and informed patients know what the
averages are without the need for this misleading study.

Posted by: *~*Wisewords | Jun 22, 2008 08:06 AM

Re: this blood glucose standards war, see

http://www.diabetesmine.com/2008/06/eag-estimated-average-glucose-glucose-standards-war.html

Posted by: AmyT of www.diabetesmine.com | Jun 22, 2008 08:02 PM

Thanks, David--I've corrected the formula.

Posted by: Tara Dairman, Web Editor | Jun 23, 2008 09:45 AM

What is the big deal? You still have to know the HbA1c in order to calculate the eAG. If you can not understand the relationship between the percentage HbA1c and your Blood Glucose levels and its impact on your health. Why would you be any more likely to understand new value that utilizes that same HbA1c in its calculation? The HbA1c is not going away no matter which you prefer. Those of satisfied with HbA1c will continue to utilize it and those who think eAG is the "answer" can ignore the HbA1c once they have done the calculation. This is just a tempest in a tea pot!

Posted by: buzzart | Jun 25, 2008 12:38 PM

The new eAG is closer to whole blood glucose averages and I prefer the plasma averages since meters are made to give out the plasma equivalent.I do not feel the study covered enough people to be accurate enough. There are just too many factors that were not figured into the equation. I wills tick with hba1c for now.

Posted by: deafmack | Jun 25, 2008 11:39 PM

Where's the BENEFIT to the eAG???

If I want my Average Blood Glucose, I can get THAT by simply downloading my GLUCOMETER readings into my computer, and telling the software to display my AAG (Actual Average Glucose) at MUCH LOWER COST than the cost to get the HgA1c test, then use a formula to arrive at an ESTIMATED Average Glucose reading...

But then again, I can also CALCULATE my Estimated HgA1c using my meter's indicated Average Glucose reading.

And over the past THREE YEARS, EVERY TIME, my calculated A1c result has ALWAYS been within 0.2 of the blood test resulting A1c reading. Meaning my formula to calculate my A1c reading based on Average Glucose Reading has proven at least 95% more reliable than their formula to arrive at an Average Glucose Reading calculated from the A1c test result.

Posted by: rcmodelr | Jun 26, 2008 02:14 PM

The A1C is a plasma blood result that is done in a lab. I believe a blood sugar average from this result would be easier for patients to understand. Most patients seen in our Diabetes Education do not understand what an A1C is. I am in favor of the eAG.

Posted by: Annette | Jul 11, 2008 02:58 PM

Tara,
Can you tell me about how long I should wait after donating red blood cells before the A1c test results would again be accurate? I assume that the donation of red blood cells would affect the A1c results, but I could be wrong. (I donate two bags of red cells and they return the plasma.) I trust your organization would be aware of any impact donation would have on the A1c.

Posted by: stuartgoldman | Jul 13, 2008 04:53 PM

sir there, I printed five pages , and second page with blank column, it printed match mixed in third page. printed about what's your eAG? you'll know soon....

Eugene Zenzen

Posted by: ekzen@aol.com | Jul 16, 2008 11:46 PM

Hi Eugene,

To print more easily, click on "Print" up at the top right-hand corner of the blog entry (next to "Text Size"). This displays the Printer-friendly version of the entry.

Posted by: Tara Dairman, Web Editor | Jul 17, 2008 10:03 AM

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