Doctors use diabetes test A1C as diagnostic tool

By Mary Brophy Marcus, USA TODAY
A test that doctors have been using for years to monitor blood sugar in people with diabetes may soon be recommended as a tool for diagnosing the disease.

Within the next six months, a consensus by several leading diabetes organizations will lead to the publication of guidelines recommending the A1C test as a diagnostic tool for type 2 diabetes, says Matt Petersen, director of information resources for the American Diabetes Association.

"Right now there are no criteria for A1C use in diagnosing diabetes, but we know it is being used in practices this way," Petersen says.

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The ADA guidelines currently recommend doctors use the fasting blood glucose (FBG) test in patients who are at risk for type 2 diabetes. A less common practice is for doctors to require an oral glucose tolerance test (OGTT).

Both are sensitive at measuring real-time glucose levels in the blood, but results can be easily thrown off, for example, if a person has a cold or hasn't eaten properly, says Daniel Einhorn, medical director of Scripps Whittier Diabetes Institute in La Jolla, Calif., and vice president of the American Association of Clinical Endocrinologists.

The benefit of the A1C test is that it can be taken at any time of day and is not thrown off by events of the day, Einhorn says. It probably would be used along with other tests.

Also called the HbA1c or glycated hemoglobin test, it tells what your average blood glucose level was over the past two or three months by measuring the concentration of hemoglobin molecules in your red blood cells that have glucose attached to them. The test also can predict the chance for future complications, such as nerve, eye and kidney damage.

Once glycated, or sugar-coated, the hemoglobin stays that way throughout the red blood cell's life span, which is about 120 days. So, if your A1C is an 8, that means 8% of your hemoglobin molecules are glycated. People who don't have diabetes typically have about a 6 or less reading. Higher results may indicate diabetes.

The only thing that has kept the reliable test from becoming a standard diagnostic tool is that the major diabetes groups have not yet agreed on what result constitutes a diagnosis.

Richard Wender, chairman of the department of family and community medicine at Thomas Jefferson University Hospital in Philadelphia, says: "We've been using A1C pretty liberally for screening in primary care and interpreting it based on our best judgment." Wender says he looks forward to a final consensus.