The American Diabetes Association (ADA) recommended in their 2010 guidelines that A1C screening for diabetes be used to test for pre-diabetes; that is, people with a high risk of developing type 2 diabetes. Early testing is important, because type 2 diabetes (unlike type 1) develops slowly over time and there may not be symptoms in the beginning stages. The A1C screening for diabetes shows the average blood sugar levels in the body over a period of a few months, and this can be done with a simple blood test that does not require fasting or any special preparation. However, while it is convenient and highly regarded, there are some limitations.
A1C Screening Limitations
Certain limitations in A1C screening for diabetes have been discovered by various research groups. It was reported in the ADA journal Diabetes Care [http://care.diabetesjournals.org/content/early/2010/07/15/dc10-0433] that the test produced racial differences, where African Americans yielded more false positives, and white Caucasians more false negatives. They concluded that most Americans as yet undiagnosed with diabetes or prediabetes would be missed by this test. A study by U-M’s C.S. Mott Children’s Hospital found that the A1C screening for diabetes was not reliable in identifying children at high risk [http://www.sciencedaily.com/releases/2011/11/111121151552.htm]. The test missed two out of three children who were known to have diabetes. Researchers are studying other non-fasting tests, such as the glucose challenge and random glucose tests, to see if there is a more accurate alternative for diabetes testing in children. The A1C screening for diabetes should not be given to women who are pregnant, people with blood disorders like anemia, those who have had recent severe bleeding or blood transfusions, and people with chronic kidney or liver disease.
What is the Best Test for Diabetes?
Is the A1C screening for diabetes the best test available? For diagnosing diabetes in children, it has been found to be less accurate than for adults, so it is best not to rely on this one test, especially if there are other risk factors, such as a family history of the disease, high cholesterol or blood pressure. Studies have shown that for adolescents, the fasting glucose test found more cases of diabetes and prediabetes than did the A1C test. The fasting glucose test, otherwise known as the oral glucose tolerance test (OGTT), is still believed to be the most accurate. Research is underway to find more accurate non-fasting testing methods for diabetes screening. One of the most recent discoveries is a non-invasive test that checks the person’s skin for diabetes biomarkers [http://www.thedenverchannel.com/health/30033234/detail.html]. The person places their arm on a portable machine, which uses light to detect the optical signature that indicates the presence of diabetes. However, as this system is still being tested, it likely won’t be approved by the FDA for general use until 2013.
