Dr David Nathan

Discussing the expected change here at the American Diabetes Association (ADA) 2007 Scientific Sessions last week, Dr David Nathan (Harvard University Medical School, Boston, MA) said that "patients have a glucose problem, not a hemoglobin problem" and that fasting glucose would be a better measure, as this new value "would help them understand their disease better." Reporting glycohemoglobin results as an A1_c-derived average glucose, said Nathan, would have the advantage of reporting chronic glycemia in the same units as the patients' self-monitoring of daily glycemia.

Nathan is the lead investigator of the international ADAGE trial, a study performed to confirm the relationship between average glucose and HbA1_c levels. To date, only a few studies with relatively infrequent glucose monitoring support a strong mathematical relationship between average glucose and HbA1_c, but if a switch is to be made from HbA1_c to average glucose levels, an international study is needed to establish the relationship across diabetes type, races, and ethnicities, said Nathan.

The ADAGE study, conducted at 10 centers in North America, Europe, and Africa, has almost completed recruitment, but Nathan presented preliminary results to the media and later during an ADA plenary session. The results of the first 250 subjects who have completed the study showed a close correlation between HbA1_c values at three months and average blood glucose during the same period. This relationship appeared to be the same for patients with type 1 and type 2 diabetes, said Nathan. The ADAGE investigators expect to present the final results of the study at the European Association for the Study of Diabetes this September.

Dr Richard Kahn, the chief scientific and medical officer of the ADA, said the change is not yet a foregone conclusion, and while there is "always concern when you change the currency," he believes that switching from reporting HbA1_c to average blood glucose levels will help patients better understand their disease and the importance of maintaining a healthy diet and lifestyle. Laboratories will still report the HbA1_c values, in addition to the new average glucose levels, but Kahn said an educational campaign would ensure that patients learn about the switch to average glucose and what these new values mean. The switch to average glucose wouldn't likely occur until sometime in 2008.

In a technical addition, Nathan and Kahn shed some light on a new standardization of the HbA1_c measurement, a process that involves better calibration of the machines to more accurately reflect HbA1_c. However, this recalibration is a "behind-the-scenes" process and won't be observed at the clinical or patient levels, they said.