Race May Affect A1C Levels
< Jun. 16, 2010 > -- Management of blood sugar levels over the long term is assessed with the hemoglobin A1C test in people with diabetes. However, a new study finds that the test may have different results depending on race, even if daily blood sugar levels are the same.
In addition, the new research suggests those differences became greater as blood sugar levels and A1C increased.
The study is published this week in the Annals of Internal Medicine.
"We found that those who self-identify as black, on average, had higher A1Cs than those who self-identify as white," says study author Dr. David Ziemer, an associate professor in the division of endocrinology and metabolism at the Emory University School of Medicine in Atlanta.
Hemoglobin is a component of red blood cells. It is hemoglobin that makes blood red, and its primary function is to carry oxygen from the lungs to the rest of the body. If hemoglobin comes into contact with sugar, which is what occurs when blood sugar levels are too high, the sugar molecules attach themselves to the hemoglobin. The hemoglobin A1C test measures what percentage of your hemoglobin is combined with sugar (glycated).
A normal A1C level is generally between 4 percent and 5.7 percent. A level between 5.7 percent to 6.4 percent is considered prediabetes, according to the American Diabetes Association, and an A1C level of 6.5 percent or higher means that you have diabetes.
However, certain factors can affect A1C readings. Medical conditions, such as certain anemias and other conditions that can affect red blood cell counts, can cause variations in A1C readings, according to an accompanying editorial in the same issue of the journal.
Adding to Earlier Research
Previous research had already found higher A1C levels in African Americans, but researchers suspected it was due to other factors, such as body-mass index levels (overweight or obesity), socioeconomic factors, or differences in diabetes control.
To assess whether or not A1C levels are affected solely by race, or if other factors might play a role in the difference, Dr. Ziemer and his colleagues ran A1C tests, a random blood glucose test, and an oral glucose tolerance test on almost 1,600 African-American and Caucasian volunteers between 18 and 87 years old. None had been previously diagnosed with diabetes.
The researchers also reviewed A1C and glucose tolerance test data from almost 2,000 people included in the Third National Health and Nutrition Survey (NHANES). Everyone in that US study was over 40 years old.
In both studies, the researchers found that African Americans had higher A1C levels than whites, even in the presence of normal blood sugar readings. In the first study, African Americans without diabetes had an average A1C that was increased by 0.13 percent. In the NHANES group, the difference between African Americans and Caucasians was 0.21 percent. Even that seemingly small difference, however, could change the diagnosis of prediabetes or diabetes, experts note.
In those with prediabetes, A1C levels in African Americans were 0.26 and 0.30 percent higher, respectively. And, for those with diabetes, the average A1C level for African Americans was 0.47 percent above that of Caucasians in both studies.
Further Analysis Needed
Dr. Ziemer says there are numerous potential mechanisms to explain why African Americans might have higher A1C levels, but nothing has been proved to date.
"This was a very interesting analysis that really needs more explanation," says Dr. Richard Bergenstal, president of medicine and science for the American Diabetes Association.
He suggests that another study - this time conducted with continuous glucose monitoring, a way of measuring blood sugar every few minutes - could measure blood sugar levels over the lifespan of an A1C, allowing researchers to see if blood sugar levels really are comparable for A1C levels, as has been previously thought.
"Among people without diabetes, these differences won't make much of a difference," explains Dr. Ziemer. "But, when you get up to the level of diabetes, will the average A1C difference of 0.4 or 0.5 percent translate into an increased risk of complications?"
Furthermore, he worries that people may be labeled as having poorer control of their diabetes because their A1Cs are higher.
Always consult your physician for more information.
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Monitoring Blood Sugar
Blood glucose levels (also called blood sugar levels) are signs of how well diabetes is being controlled and how well the plan of care (diet, exercise, and medication) is working. If the blood sugar levels are consistently under control (with levels near normal), diabetes complications may be prevented or slowed down in their progression.
Checking blood glucose levels regularly is very important in proper diabetes management. Current methods of blood sugar monitoring require a blood sample. Blood sugar monitoring can be done at home with a variety of invasive devices to obtain the blood sample (invasive means the penetration of body tissue with a medical instrument).
Usually a drop of blood obtained through a finger prick is sufficient to use on a test strip that is then measured in a monitor. A finger prick can be done with a small lancet (special needle) or with a spring-loaded lancet device that punctures the fingertip quickly. The drop of blood is placed on a testing strip. The testing strip is then placed in a blood glucose monitor (also called a glucose meter) which reads the blood sugar level.
There are many types of monitors on the market today, ranging in price, ease of use, size, portability, and length of testing time. Each monitor requires its own type of testing strip. Blood glucose monitors have been found to be accurate and reliable if correctly used, and most monitors provide results within two minutes. Some glucose monitors can also give verbal testing instructions and verbal test results for people who are visually or physically impaired. There are also glucose monitors available that provide verbal instructions in Spanish and other languages.
People with diabetes may have to check their blood sugar levels up to four times a day. Blood sugar levels can be affected by several factors, including the following:
Certain blood glucose monitors are equipped with data-management systems, which means your blood glucose measurement is automatically stored each time. Some physician offices have computer systems compatible with these data-management systems, which allow the blood sugar level recordings, and other information, to be transferred electronically. One advantage of a data-management system is the ability to plot a graph on the computer depicting patterns of blood sugar levels.
Always consult your physician for more information.
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