Study Questions Diabetes Threshold

American Diabetes Association Plans to Review Fasting Glucose Benchmark for Diabetes Diagnosis

Medically Reviewed by Louise Chang, MD on February 29, 2008
From the WebMD Archives

Feb. 29, 2008 -- A guideline for type 2 diabetes diagnosis is getting questioned in a new report.

Writing in The Lancet, researchers report that their findings "suggest that the criteria for diagnosing diabetes could need reassessment."

But not everyone agrees.

The new report "raises more questions than answers" and until a better benchmark becomes available, "we are probably best sticking with what we know," states an editorial published with the study.

The American Diabetes Association and its international partners had already planned to discuss the issue in May, according to M. Sue Kirkman, MD, vice president for clinical affairs at the American Diabetes Association.

Retinopathy Review

The new report is based on data from three studies that together included 11,423 adults in the U.S. and Australia.

Participants provided blood samples after fasting. They also got high-tech photos taken of their eyes to look for signs of retinopathy, which is damage to blood vessels in the eye's retina.

Retinopathy is a common complication of uncontrolled diabetes. But it isn't always caused by diabetes.

Most participants didn't have retinopathy. The percentage with retinopathy varied among the studies, ranging from about 10% to 15%.

Retinopathy was more common among people with higher fasting glucose levels. But there was no clear benchmark for fasting glucose levels among retinopathy patients.

More than 60% of the people with retinopathy didn't have fasting glucose levels in the range that is used to help diagnose type 2 diabetes, prompting the reviewers to question the use of that fasting glucose standard for type 2 diabetes diagnosis.

The reviewers included Tien Wong, MD, of the Centre for Eye Research Australia at the University of Melbourne.

Diabetes Diagnosis: What Is the Alternative?

"While interesting, Wong and colleagues' study offers no alternative criteria," states an editorial published with the study.

"We perhaps should focus less on a single universal cutoff" and instead focus on individual risk factors, the editorialists suggest.

"But what would we tell our patients when they asked if they had diabetes? We are probably best sticking with what we know until a better alternative diagnostic tool becomes available," conclude the editorialists.

They included Quresh Mohamed, MD, of England's Cheltenham General Hospital.

Expert: Diabetes Risk Is Not Fixed

The study's data "are not so dramatically different from previously available data," Professor John Buse, MD, PhD, tells WebMD via email.

Buse is chief of the endocrinology division and director of the Diabetes Care Center at the University of North Carolina at Chapel Hill. He is also the American Diabetes Association's president for medicine and science.

Buse points out that in many cases, thresholds don't determine risk. For example, he mentions the threshold for LDL "bad" cholesterol, which should ideally be less than 100 to help prevent heart disease.

"People with an LDL cholesterol of 99 are not immune from heart disease and those with an LDL of 101 are not doomed," writes Buse. "It's not as if there is a cliff and if you ever cross the threshold you fall off. All these 'diseases' are defined by arbitrary cutpoints in what are otherwise continuous variables with fairly graded risk well into the 'normal' range."

Buse adds that two working groups at the American Diabetes Association are looking into the issues raised by the paper about diabetes screening and diagnosis.

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Wong, T. The Lancet, March 1, 2008; vol 371: pp 736-743.

Mohamed, Q. The Lancet, March 1, 2008; vol 371: pp 700-702.

Email from M. Sue Kirkman, MD, vice president, clinical affairs, American Diabetes Association.

Email from Richard Kahn, PhD, chief scientific & medical officer, American Diabetes Association.

Email from John Buse, MD, PhD, chief and professor, division of endocrinology and director, Diabetes Care Center, University of North Carolina at Chapel Hill; president, Medicine & Science, American Diabetes Association.

National Eye Institute: "Diabetic Retinopathy."

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