ADA: Diabetes Yardstick Gets New Look

CHICAGO, June 27 -- Now that physicians are growing familiar with glycosylated hemoglobin percentages, average glucose levels are rising to the fore, investigators here reported.

The new standard, which involves more of a technical than clinical change, involves a more accurate calculation of HbA1c in the lab, but reporting of results as both HbA1c and an average glucose level, said David Nathan, M.D., of Harvard.

The technical change has already been performed behind the scenes, with clinical labs and manufacturers calibrating their equipment to the new standards, Dr. Nathan and colleagues reported at the American Diabetes Association meeting here.

Dr. Nathan presented preliminary results of an international study looking at whether the new HbA1c standard can be accurately and consistently translated into average glucose.

"It sounds technical and somewhat dry, but from the point of view of diabetes management, this is something that has been absolutely dominating our interest and attention -- clinical chemists, clinical pathologists, and clinicians, and investigators -- for a couple of years now," Dr. Nathan said.

There was concern among physicians that patients would be confused by the new measurement, which would effectively change an HbA1c of less than 7% (the current ADA standard) from an "A" to a "C-," Dr. Nathan said.

To prevent that confusion, the world's leading diabetes organizations -- the ADA, European Association for the Study of Diabetes, and International Diabetes Federation -- agreed on a means for translating the new measurement into a uniform reference number.

The reference number can then be translated into the familiar HbA1c values using simple mathematic formulas, and into the average blood glucose number, which may be an easier number to grasp for patients who are accustomed to daily finger sticks and blood glucose monitoring, Dr. Nathan said.

"We hope that we will have converted the hemoglobin A1c into an easily translatable value that has actually has more significance for patients," Dr. Nathan said.

The International A1c-AG study was conducted at 10 centers in the North America, Europe, and Africa, in an attempt to determine, as accurately as possible, the relationship between average blood glucose levels and HbA1c.

The study has recruited almost 650 of its goal of 700 volunteers (300 patients with type 1, 300 with type 2, and 100 without diabetes).

The patients' HbA1Cs are measured in a central laboratory in Holland using the new reference standard monthly for four months, with patients using a combination of continuous glucose monitoring for two to three days for each of the four months, plus frequent finger sticks equivalent to daily self-monitoring.

The results of the first 250 volunteers who have completed the study showed that there was a close correlation between HbA1c values at three months and average blood glucose during the same period, Dr. Nathan reported.

"The relationship appears to be the same for those with type 1 and type 2 and for men and women," Dr. Nathan said.

The investigators hope to present final results of the study at a meeting of the European Association for the Study of Diabetes in Amsterdam this September.