All about A1c (Part 2)

9:41 am Health Care

1. A1c can give false results in some people. It can be unreliable for diagnosing or monitoring diabetes in people with certain conditions that are known to interfere with the results. Interference should be suspected when A1c results seem very different from the results of a blood glucose test. People of African, Mediterranean, or Southeast Asian descent, or people with family members with sickle cell anemia or a thalassemia are particularly at risk of interference. People in these groups may have a less common type of hemoglobin, known as a hemoglobin variant that can interfere with some A1c tests. Most people with a hemoglobin variant have no symptoms and may not know that they carry this type of hemoglobin.
2. Not all of the A1c tests are unreliable for people with a hemoglobin variant. People with false results from one type of A1c test may need a different type of A1c test for measuring their average blood glucose level.
3. False A1c results may also occur in people with other problems that affect their blood or hemoglobin. For example, a falsely low A1c result can occur in people with anemia, heavy bleeding.
4. A falsely elevated A1c result can occur in people who are very low in iron, for example, those with iron deficiency anemia.
5. Other causes of abnormal A1c results include kidney failure and liver disease
6. Health care providers can use the A1c test to monitor blood glucose levels in people with type 1 or
type 2 diabetes. The A1c test is not used to monitor gestational diabetes.
7. The American Diabetes Association (ADA) recommends that people with diabetes who are meeting treatment goals and have stable blood glucose levels should have the A1c test twice a year. Health care providers may repeat the A1c test as often as four times a year until blood glucose levels reach recommended levels.
8. The A1c test helps health care providers adjust medication to reduce the risk of long-term diabetes complications. Studies have demonstrated substantial reductions in long-term complications with the lowering of A1c levels.
9. When the A1c test is used for monitoring blood glucose levels in a person with diabetes, the blood sample can be analyzed in a health care provider’s office using a POC test to give immediate results. However, POC tests are less reliable and not as accurate as most laboratory tests.
10. Estimated average glucose (eAG) is calculated from the A1c. It helps people with diabetes relate their A1c to daily glucose monitoring levels. The eAG calculation converts the A1c percentage to the same units used by home glucose meters i.e. milligrams per deciliter (mg/dL). The eAG number will not match daily glucose readings because it is a long-term average rather than the blood glucose level at a single time, as measured with the home glucose meter. (Diabetes Care 2011;34(Supp 1):S11–S61, Table 9)

A1c (%) eAG (mg/dL)
6 126
7 154
8 183
9 212
10 240
11 269
12 298

11. People will have different A1c targets depending on their diabetes history and their general health.
12. Studies have shown that people with diabetes can reduce the risk of diabetes complications by keeping A1c levels below 7%.
13. An A1c level that is safe for one person may not be safe for another. For example, keeping an A1c level below 7% may not be safe if it leads to problems with hypoglycemia.
14. Less strict blood glucose control, or an A1c between 7-8 % or even higher in some circumstances, may be appropriate in people who have limited life-expectancy; long-standing diabetes and difficulty attaining a lower goal; severe hypoglycemia and advanced diabetes complications such as chronic kidney disease, nerve problems, or cardiovascular disease
15. Large changes in a person’s blood glucose levels over the past month will show up in their A1c test result, but the A1c does not show sudden, temporary increases or decreases in blood glucose levels. Even though the A1c represents a long-term average, blood glucose levels within the past 30 days have a greater effect on the A1c reading than those in previous months.

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