If you've ever tried to explain what an A1C score means to someone who wouldn't know glycated hemoglobin from hash browns, you'll be glad to know there's a new, simpler way to talk about blood glucose levels. Instead of A1C percentages, doctors will soon start reporting to patients their eAG, or "estimated average glucose'' level.
In the last couple of years, a new international standard of the A1C test has been developed that is more precise in measuring those glycated hemoglobins. But the new test results in a "normal range'' for A1C that is 1.5 to 2% lower than the range everyone has become used to. For instance, what we call a 7% A1C would be reported as a 5% A1C with the new standard. Confused? Yes, that's what diabetes experts thought would happen. So a team of researchers in the U.S. conducted a study to define the mathematical relationship between the A1C and average glucose measurements reported in the same units everybody is familiar with from daily fingerstick monitoring -- milligrams per deciliter, or mg/dl. Diabetes experts have long assumed the A1C expressed two- to three-month average blood sugar levels, but the studies had not been done to prove it, until now.
In a press briefing today and a paper published on line in Diabetes Care, David Nathan of Harvard Medical School and colleagues report that a study involving 507 people who tested their blood sugars through continuous glucose monitoring along with fingerstick testing showed the A1C matches estimated average glucose (eAG) in both type 1 and type 2 patients.
The researchers provided a chart for comparison:
A1C of 6% equals eAG of 126 mg/dl
A1C of 6.5% equals eAG of 140
A1C of 7% equals eAG of 154
A1C of 7.5% equals eAG of 169
A1C of 8% equals eAG of 183
A1C of 8.5% equals eAG of 197
A1C of 9% equals eAG of 212
A1C of 9.5% equals eAG of 226
A1C of 10% equals eAG of 240
As it turns out, it looks likely that labs will continue to report an A1C value as we now know it, along with the new "lower" value based on the new test. But ADA and others will begin promoting the use of the term eAG and asking labs to report that value as well. Already, ADA has posted an online calculator at www.diabetes.org/AG so anyone can make the conversion from A1C to eAG at the click of a mouse. "The whole idea of this is to simplify clinical practice and education,'' says Dr. Robert Heine, a co-author of the paper. Labs may report three numbers to physicians, but "at the end of the day, one number will be reported to patients,'' he says, and it will be a number they will easily understand. With an eAG, "patients can relate what they are doing at home to what we're doing in the chemistry lab,'' he says. An accompanying editorial in Diabetes Care says the term A1C "with its current units and normal range will not vanish or change,'' but "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.''
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