International Body Aims to Adopt A1C Standardization
A worldwide standardization of the hemoglobin A1C measurement.
By Daniel Trecroci
For the seasoned person with diabetes, the term A1C is all part of the vernacular and that higher A1cs equal a greater risk for diabetes complications. For others, however, A1C is a foreign language. Many don't know that the A1C is a representation of average blood glucose over a three-month period. Furthermore, some might be confused as to what a 7% A1C might equal as an average blood glucose. Then there is the question of whether an A1C measured at one lab equals the same A1C at another.
In an effort to adopt worldwide standardization of A1C measurement, the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC)—with support from the American Diabetes Association; the European Association for the Study of Diabetes; and the International Diabetes Federation—recently developed a "Consensus Statement on the Worldwide Standardization of the Hemoglobin A1C Measurement."
The consensus statement was published in the September 2007 issue of Diabetes Care. What it notes is that:
- A1C test results should be standardized worldwide.
- The new IFCC reference system for A1C represents the only valid anchor to implement standardization of the measurement.
- A1C results are to be reported worldwide in IFCC units (mmol/mol), derived NGSP units and as A1C-derived average glucose (ADAG).
"There is a lot of confusion among patients about what a particular ‘A1C' result means," says John B. Buse, MD, PhD, CDE, president of the American Diabetes Association. "The hope is that the translation of A1C to estimated average glucose will put A1C into terms that patients are accustomed to."
Richard Kahn, PhD, the ADA's chief medical and scientific officer, says there was never any inconsistency in the way A1C has been reported thus far. Current A1C testing devices use reference methods that measure a mixture of glycated hemoglobins (e.g. hemoglobin A1c, Hb1c , HbA1c or HgA1c). However, to achieve a more uniform standardization of A1C measurements, it is desirable to have a reference method that measures only one glycated hemoglobin—in this case, A1C.
"So, an organization came along—the IFCC—and they said we have a new method to standardize the machines that will really measure A1C," says Kahn. "So now, you can calibrate your machines off of a true A1C."
Kahn likens a standardized A1C testing method to a tire-pressure gauge. "You have these instruments like a tire-pressure gauge, and it comes out with a reading of 22. And you want to know when a 22 is really 22," says Kahn. "So it has to be standardized against a reference method that will make that little thing pop out when it is actually at 22 pounds of pressure in the tire."
In short: Standardized A1C testing methods ensure that a 7% A1C is really a 7% A1C.
As for glycemic goals appearing in clinical guidelines being expressed in IFCC units, Kahn notes that the worldwide endocrinology community did not like the idea.
"So we said, well how about if we express things according to the estimated average glucose? Because that is really what the A1C is supposed to represent."
Kahn's guess is that nobody is going to want to use the IFCC method of A1C results reported in worldwide units (mmol/mol).
"Some might choose to have the machine convert the IFCC number to the old A1C number and many—I hope most, if not all—will choose to take the A1C number and convert it to an estimated average glucose number.
What does this mean to patients who might be confused as to what A1C is in the first place? John Buse says there will need to be a massive professional and patient education campaign to facilitate this understanding of A1C standardization. Kahn says it will be easy for some patients and hard for others.
" If the lab chooses to report to a clinician the A1C as an ‘estimated average glucose,' it should be really easy for the patient to understand. Now for patients who have been with diabetes for a number of years, who understand what an A1C is and look forward to getting their results, there might be some confusion [if their doctor says], ‘Well, your estimated average glucose is 162.'".
Kahn says that, for some time, there might be a cheat sheet available to doctors and patients that explains estimated average glucose as a measure of A1C or vice versa.
The American Diabetes Association; European Association for the Study of Diabetes, and International Diabetes Federation feel that the A1C standardization recommendations be implemented globally as soon as possible.
For a complete listing of all of the topics from the Diabetes Technology Meeting, log on to http://www.diabetestechnology.org.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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