A1c Test Identifies Diabetes, Heart Risk

Study Shows Non-Fasting Diabetes Test More Accurate Than Blood Glucose Test

By Daniel J. DeNoon
WebMD Health News

Reviewed By Laura J. Martin, MD

March 3, 2010 -- You don't have to fast before taking the newly recommended A1c test to screen for diabetes -- and it spots early diabetes and heart disease better than the older test, researchers find.

Late last year, the American Diabetes Association recommended using the A1c test to screen for diabetes. The test had been around for decades, but recent standardization made it useful as a screening tool.

And now there's convincing evidence that A1c outperforms the older test, which measured blood sugar (glucose) in people who had fasted for eight hours. It comes from a study in which Johns Hopkins researcher Elizabeth Selvin, PhD, MPH, and colleagues compared results of both tests in 11,000 adults screened with both tests.

A1c "was similarly associated with a risk of diabetes and more strongly associated with risks of cardiovascular disease and death from any cause as compared with fasting glucose," Selvin and colleagues report.

The ADA says that an A1c level at or above 6.5% means you have diabetes. Selvin's team showed that the risk of diabetes, heart disease, and death rises with A1c.

Compared to people with a normal A1c level of 5.0% to 5.5%, they found that:

  • An A1c level of less than 5.0% means a 48% lower risk of diabetes and about the same risk of heart disease.
  • An A1c level of 5.5% to 6.0% means an 86% higher risk of diabetes and a 23% higher risk of heart disease.
  • An A1c level of 6.0% to 6.5% means a 4.5-fold higher risk of diabetes and a 78% higher risk of heart disease.
  • An A1c level of 6.5% or more means a 16.5-fold higher risk of diabetes and a twofold higher risk of heart disease.

A1c stands for glycated hemoglobin. The A1c percentage measures how much sugar is attached to the blood's hemoglobin protein. The A1c test result gives a measure of how well your body has controlled the amount of sugar in the blood over the past two to three months.

For this reason, the A1c test is not as prone as the fasting glucose test to individual fluctuations due to stress or illness. But it is more expensive, and the test can be misleading in patients with certain forms of anemia.

The Selvin study appears in the March 4 issue of the New England Journal of Medicine.

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SOURCES: Selvin, E. New England Journal of Medicine, March 4, 2010; vol 362: pp 800-811.

WebMD Health News: "A1C Blood Test OK for Diabetes Diagnosis."

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