ADA 2009: Expert Committee Recommends Use of Hemoglobin A1C for Diagnosis of Diabetes

Martha Kerr

June 07, 2009

June 7, 2009 (New Orleans, Louisiana) — The American Diabetes Association (ADA), the International Diabetes Federation (IDF), and the European Association for the Study of Diabetes (EASD) have joined forces to recommend the use of the hemoglobin A1C assay for the diagnosis of diabetes.

The international expert committee's recommendations were announced here on Friday during the opening hours of the ADA's 69th Scientific Sessions and released simultaneously online in the July issue of Diabetes Care.

"This is the first major departure in 30 years in diabetes diagnosis," committee chairman David M. Nathan, MD, director of the Diabetes Center at Massachusetts General Hospital and professor of medicine at Harvard Medical School in Boston, declared in presenting the committee's findings.

"A1C values vary less than FPG [fasting plasma glucose] values and the assay for A1C has technical advantages compared with the glucose assay," Dr. Nathan said. A1C gives a picture of the average blood glucose level over the preceding 2 to 3 months, he added.

"A1C has numerous advantages over plasma glucose measurement," Dr. Nathan continued. "It's a more stable chemical moiety.... It's more convenient. The patient doesn't need to fast, and measuring A1C is more convenient and easier for patients who will no longer be required to perform a fasting or oral glucose tolerance test.... And it is correlated tightly with the risk of developing retinopathy."

A disadvantage is the cost. "It is more expensive," Dr. Nathan acknowledged. However, cost analyses have not been done, "...and costs are not the same as charges [to the patient]."

The committee has determined that an A1C value of 6.5% or greater should be used for the diagnosis of diabetes.

This cut-point, Dr. Nathan said, "is where risk of retinopathy really starts to go up."

He cautioned that there is no hard line between diabetes and normoglycemia, however, " A1C level of 6.5% is sufficiently sensitive and specific to identify people who have diabetes."

"We support the conclusion of the committee, that this is an appropriate way to diagnose diabetes," stated Paul Robertson, MD, president of medicine and science at the ADA and professor of medicine at the University of Washington in Seattle.

"Now, we have to refer the committee's findings to practice groups for review of the implications and for recommendations," Dr. Robertson told Medscape Diabetes & Endocrinology after the committee's presentation.

"We purposely avoided using estimated average glucose, or EAG, as this is just a way to convert the A1C into glucose levels.... And one thing we want to try to get away from is the term prediabetes," Dr. Nathan said. "It suggests that people with it will go on to get diabetes, but that is not the case."

"We don't know if we will be diagnosing more patients with diabetes or less, with AIC," Dr. Nathan commented. Cut-off values or practice guidelines have not been established. More study needs to be done first, but "physicians should not mix and match A1C and blood glucose levels. They should stick with one in reviewing a patient's history," Dr. Nathan asserted.

"There is no gold standard assay," said session moderator Richard Kahn, PhD, chief medical and scientific officer of the ADA, which is headquartered in Alexandria, Virginia. "All of these tests measure different things. They all have value. But A1C is the best test to assess risk of retinopathy."

"We [the ADA] are not issuing a position statement at this time," Dr. Robertson stressed when speaking with Medscape Diabetes & Endocrinology. "It is too soon to write a position paper yet. We need to know what we are getting into first."

"Some parts of the world are not going to be able to use this," Dr. Robertson added. "It may be too expensive to use in the developing world. Some of these countries have severe chronic anemia, hemolytic anemia, and so on, where we will have to fall back on traditional tests. We are being very cognizant of the international implications." A1C assays are inaccurate in cases of severely low hemoglobin levels.

"We don't think physicians will have a hard time adopting the test...a lot of them are doing it already. We think it will only take a couple of years to be adopted widely into clinical practice," Dr. Kahn told Medscape Diabetes & Endocrinology. "Physicians won't be shocked by this report, but patients — and insurance companies — might be. There are wider social issues that haven't been looked at yet."

None of the speakers at this session disclosed any relevant financial relationships.

American Diabetes Association (ADA) 69th Scientific Sessions. Presented June 5, 2009.

Diabetes Care. Published online June 5, 2009.