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Hemoglobin A1c Levels Differ in Black and White Persons Independent of Glucose Level FREE

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The summary below is from the full report titled “Glucose-Independent, Black–White Differences in Hemoglobin A1c Levels. A Cross-sectional Analysis of 2 Studies.” It is in the 15 June 2010 issue of Annals of Internal Medicine (volume 152, pages 770-777). The authors are D.C. Ziemer, P. Kolm, W.S. Weintraub, V. Vaccarino, M.K. Rhee, J.G. Twombly, K.M.V. Narayan, D.D. Koch, and L.S. Phillips.

Ann Intern Med. 2010;152(12):I-24. doi:10.7326/0003-4819-152-12-201006150-00001
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What is the problem and what is known about it so far?

Hemoglobin is the protein in red blood cells that makes them red. Its principal function is to carry oxygen from the lungs to other parts of the body. When hemoglobin comes into contact with sugar, they combine to form hemoglobin A1c. The more sugar in the blood, the higher the hemoglobin A1c level. Normal values range from 4.0% to 5.9%. Clinicians use hemoglobin A1c levels to estimate the average blood sugar during the previous 4 weeks to 3 months. Because patients with untreated diabetes have elevated levels of blood sugar, clinicians can use the hemoglobin A1c level to determine whether a patient has diabetes and whether patients with diabetes are being treated adequately. Although black persons have higher hemoglobin A1c levels than white persons, most observers thought that was because blood sugar levels were higher in black persons than in white persons. Recently, 3 studies have found that in patients with diabetes or a condition that leads to diabetes, black persons have higher hemoglobin A1c levels than white persons with the same blood sugar levels.

Why did the researchers do this particular study?

To find out whether hemoglobin A1c levels are higher in black persons than in white persons when they do not have diabetes or a condition that leads to diabetes.

Who was studied?

1581 non-Hispanic black and white persons in the Atlanta area between 18 and 87 years of age who did not have known diabetes and were well enough to work and 1967 non-Hispanic black and white persons older than 40 years without known diabetes, who were otherwise representative of the U.S. national population.

How was the study done?

Research staff interviewed and examined people and drew blood that was tested for sugar and hemoglobin A1c.

What did the researchers find?

Black persons had higher hemoglobin A1c levels than white persons with similar sugar levels regardless of whether they had diabetes, a condition that leads to diabetes, or neither condition. The differences between black and white persons increased as sugar levels increased.

What were the limitations of the study?

We do not know why the black–white differences occurred.

What are the implications of the study?

Race affects hemoglobin A1c levels, which should change the way we use hemoglobin A1c testing to screen for diabetes, predict the risk for complications from diabetes, and measure quality of care.





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