Clarity on control (American Diabetes Assn. Scientific Sessions)
■ The ADA plans to roll out a new method of reporting hemoglobin A1c results -- one it hopes will be easier for patients to understand.
By Amy Snow Landa — Posted Aug. 6, 2007
When you tell a patient her hemoglobin A1c result is 8%, how does she relate that number to the blood glucose levels she measures at home in units of mg/dL? Is an A1c of 8% equivalent to an average glucose of 180?
As if diabetes management isn't complicated enough, dealing with different types of blood glucose measures can make it more so.
The American Diabetes Assn. hopes that a new method of reporting A1c results will help clear up the confusion.
The ADA plans to begin encouraging physicians later this year to tell patients their A1c results in "average glucose" units that are the same units patients use in self-monitoring.
The idea is to make it easier for patients to understand their A1c results by reporting them in units that are familiar, said Richard Kahn, PhD, the ADA's chief medical and scientific officer.
It should make the physician's job easier as well, Dr. Kahn said during a news conference at the ADA's annual scientific sessions June 22-26 in Chicago.
"It's just too complicated to explain to someone what a hemoglobin of 7% means and how it relates to [his] 140, 150, 180," he said. "It's so much easier to say to someone they've got an average glucose of X."
Waiting for trial results
But before rolling out its new initiative, the ADA is waiting for the final results of an international clinical trial aimed at determining whether hemoglobin A1c accurately reflects average blood glucose.
Reporting A1c results in average glucose units requires certainty about the correlation between the two numbers, explained David M. Nathan, MD, director of the Diabetes Center and the General Clinical Research Center at Massachusetts General Hospital and professor of medicine at Harvard Medical School.
That certainty has been elusive in the past, Dr. Nathan said. Previous studies were based on infrequent glucose monitoring, which meant there was a possibility of sampling error. So researchers weren't sure if an A1c of 5% represented a blood sugar of 80, 90 or 100, or if an A1c of 10% was a 200, 250 or 300, he said.
But the ADA, in cooperation with the European Assn. for the Study of Diabetes and the International Diabetes Foundation, is finishing up a clinical trial that may eliminate that uncertainty for good.
The International A1c-AG Study involves 10 diabetes centers in the United States, Europe and Africa that have recruited more than 600 diabetic and nondiabetic patients of various races and ethnicities. Researchers use continuous glucose monitoring and frequent finger sticks to measure average glucose levels over four months and compare them with patients' A1c levels.
Final results will be announced in September. But the preliminary findings, reported at the ADA meeting, are very encouraging, Dr. Nathan said. "As we had thought, based on incomplete evidence in the past, in fact there is a tight correlation between average blood glucose and hemoglobin A1c results. And we can use that tight correlation to provide a transformation of the A1c value into an actual blood glucose."
Assuming that the preliminary results hold up, the ADA, EASD and IDF will convene a committee in late summer or early fall to draft a template for converting A1c results to average glucose units.
But it won't be an overnight transformation. It will take time to recalibrate lab machines to produce A1c results in the new units. In the meantime, the ADA plans to offer a "cheat sheet" to help doctors convert A1c percentages into average glucose units, Dr. Kahn said.
Doctors and patients also can choose to stick with the current system, Dr. Kahn said. Even after the machines are recalibrated, doctors still will get a printout that includes the A1c as a percentage. "So if you have a reluctant patient who says, 'I don't want to know what my average is, I want to know what my A1c is,' then the physician will have it."
But both Dr. Kahn and Dr. Nathan predict that over time most patients and doctors will realize how much easier it is to track average glucose.
And that should help improve patients' management of their diabetes, Dr. Nathan said. "To have the average level given as the same units as their everyday measurements just seems to me inherently a good thing."