Experts Urge One Test to Diagnose Diabetes

07 june 2009-- The A1C test, which measures average blood glucose levels over a period of two to three months, should now be the main tool doctors use to diagnose diabetes, an international expert panel recommended Friday.

Besides giving a more accurate picture of diabetes risk, the A1C test is easier on patients than older tests, which often required fasting.

Individuals with hemoglobin A1c values at or above 6.5 percent can be considered to have diabetes, although that number is not set in stone, the experts stated at the American Diabetes Association (ADA) annual meeting in New Orleans.

"This is the first major departure from the way that we've been diagnosing diabetes for more than 30 years, using a laboratory tool that is slightly different than the acute [short-term] measurement of glucose -- measurement of a single glucose value -- which has been traditionally used," said Dr. David Nathan, chairman of the committee and director of the diabetes center at Massachusetts General Hospital in Boston.

He spoke at a special press conference at the ADA meeting on Friday.

The committee comprised members of the ADA, the International Diabetes Federation and the European Association for the Study of Diabetes, although these organizations have not yet issued position statements on the recommendations.

The ADA did, however, speak out unofficially in support of the conclusions.

"We support the conclusions of the paper that basically says that the A1c measurement is appropriate for diagnosing diabetes," said Dr. Paul Robertson, president of medicine and science for the ADA. "Right now, our focus is what comes next. What does this mean for diabetes?"

The guidelines will be referred to practice committees before an official statement is issued, he said.

The proposed diagnostic guidelines will also appear in the July issue of Diabetes Care.

Currently, two tests are widely used to diagnose type 2 diabetes, which now afflicts some 24 million Americans: fasting plasma glucose or oral glucose tolerance tests. Both look at short-term blood glucose levels and involve some inconvenience to patients, including fasting for periods of time before blood is drawn.

Blood glucose levels are also notoriously fickle, changing depending on how recently the patient exercised or ate a meal or snack. Blood sugar can also fluctuate if a person has a cold or if the blood sample is kept at room temperature or in a colder environment.

So, "the results are sometimes difficult to interpret," Nathan said. "With A1C, it doesn't really matter. We consider this a preferred method of diagnosing diabetes. It doesn't care what blood glucose levels are after dinner, before dinner, if you have a cold. It integrates all those levels."

The committee based its recommendations on a review of the literature, focusing on what A1C levels were more likely to result in diabetic retinopathy, a vision-threatening eye condition that is one potential complication of the disease.

"Diabetes is associated with both elevated levels of blood sugar and a host of complications and the one we can measure most quantitatively is retinopathy," Nathan explained. "Glucose levels span an enormous distribution. There's no clear-cut point. To pick a dividing line, we looked at glucose levels associated with this complication."

"After reviewing lots of clinical chemistry data, we determined that there are numerous advantages of A1C," he continued.

People with A1C levels between 6 and 6.5 percent are considered to be at higher risk for diabetes, the committee said.

Experts speaking at the teleconference emphasized that the conventional blood glucose tests are not to be discarded, especially in areas of the world where A1C testing might not be available.

"We're not discarding those tests. We just think that A1C is the preferred method in 2009, and that the world should be moving towards that universally," Nathan said.

Many physicians have already been doing so, added Dr. Spyros Mezitis, an endocrinologist with Lenox Hill Hospital in New York City.

"The change is consistent with the direction practice has been going," he said. "And tight glucose control is still our focus."