Expert committee proposes HbA1c replace glucose levels for diabetes

A 21-member International Expert Committee proposes that hemoglobin A_1c (HbA_1c) assays be the mainstay of type 2 diabetes screening and diagnosis, replacing fasting blood glucose (FBG) level and the oral glucose tolerance test (OGTT). "This is the first major departure from how we've been diagnosing diabetes in the past 30 years," says David M. Nathan, MD, chair of the committee and Professor of Medicine, Harvard Medical School, Boston, MA (pictured left).

Committee members reviewed the evidence linking glycemic exposure with complications and concluded that an HbA_1c of 6.5% should be diagnostic for diabetes, says Dr. Nathan. "Diabetic retinopathy is the complication we can measure most readily, and HbA_1c correlates very closely with diabetic retinopathy.

"The committee also recommends that patients with HbA_1c levels between 6.0 and 6.5% be cautioned that they are in the highest risk group for developing type 2 diabetes. "The risk for developing diabetes is a continuum. Prediabetes is not a great term to use," Dr. Nathan says.

The report was published online yesterday and will be in the July issue of Diabetes Care.

"An HbA_1c of 6.5% is the level above which you see eye disease and below which you don't see it," explains Paul Robertson, president, Medicine and Science, American Diabetes Association (pictured left). He says the ADA practice working group will review the new recommendations along with international organizations and associations including the Centers for Disease Control and the World Health Organization. "We are very keen on being sure we are inclusive of the world on this," Robertson says. "This is very important in the context of the recent epidemic of diabetes."

Distinct advantages seen

Although glucose levels have been used to diagnose type 2 diabetes traditionally, using HbA_1c has definite advantages. HbA_1c reflects the average glucose level over a period of several months, whereas glucose levels only measure one point in time. "HbA_1c is also a more stable chemical moiety; glucose levels can change with temperature and time," Dr. Nathan said.

HbA_1c testing is also much more convenient for patients and eliminates the need for 8-hour fasting before a blood glucose level is taken or an oral glucose tolerance test is administered.

However, cost may be a concern. Currently, a patient is charged $4 or $5 for a laboratory glucose test, and an HbA_1c assay costs double to triple that amount, says Dr. Nathan. "Patients diagnosed with glucose levels now go on to have an HbA_1c assay, so using HbA_1c for screening would serve as their baseline measurement," he says.

Members of the International Expert Committee were appointed by the ADA, the European Association for the Study of Diabetes, and the International Diabetes Federation.