In addition to diagnosing type 2 diabetes based on fasting blood glucose levels or a glucose tolerance test, the American Association of Clinical Endocrinologists (AACE) and the American College of Endocrinology (ACE) have now approved the use of A1c as an additional diagnostic criterion for type 2 diabetes.

The AACE decision was released in a position statement entitled "The AACE/ACE Statement on the Use of A1c for the Diagnosis of Diabetes", which can be found online here. The position statement also reviews the limitations of the test, such as certain ethnic groups having marginally elevated values, which do not necessarily indicate diabetes.

The A1c or hemoglobin A1c (HbA1c) test determines the average level of blood glucose over a 3-month period.  How does that work? Red blood cells contain a protein called hemoglobin A, which is the actual carrier of oxygen in the blood. Glucose in the blood also attaches to the protein (or glycates the protein).  More glucose in the blood means more of it can to stick to the hemoglobin A protein.  Once a hemoglobin molecule is glycated, it stays that way. And since hemoglobin A can survive in the bloodstream for about 3 months, measuring the amount of glycated hemoglobin gives you an average amount of glucose in the blood over about a 3 month period. An A1c of 7.0 indicates that 7 percent of the hemoglobin A molecules are glycated.

"Using A1c will provide doctors and patients a convenient additional tool to diagnose diabetes and thereby identify more patients with it," said Dr. Jeffrey R Garber, president of AACE, in a press release.

The most common criteria currently used to diagnose diabetes are a fasting glucose of 126 or greater, or a two-hour value on a glucose tolerance test (GTT) greater than 200. Both tests require patients to fast for a minimum of eight hours prior to being tested. The GTT is a 2-hour series of measuring glucose levels (multiple blood draws) following the administration of a large amount of glucose.

The AACE Guidelines for the Management of Diabetes use an A1c of 6.5 (meaning 6.5 percent of the hemoglobin A is glycated) or less as a goal for patients once they have been diagnosed with type 2 diabetes.

About the American Association of Clinical Endocrinologists (AACE) AACE is a professional medical organization with more than 6,000 members in the United States and 91 other countries. AACE members are physicians who specialize in endocrinology, diabetes, and metabolism. For more information about AACE, visit their web site at http://www.aace.com/.

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Sources: 

American Association of Clinical Endocrinologists: http://www.aace.com/ 

Press release http://media.aace.com/article_display.cfm?article_id=4942