According to the American Diabetes Association, an international expert committee recommends the A1c blood test as the gold standard for diabetes testing. As of June 5, 2009, the American Diabetes Association, the International Diabetes Federation and the European Association for the Study of Diabetes have yet to adopt the recommendation. The committee says the A1c test should replace the glucose tolerance test, which requires several blood draws and fasting conditions. Doctors continue to have many tests at their disposal that measure blood sugar levels.
Types of Tests
The fasting blood sugar test, the glucose tolerance test, or GTT, and the glycosylated hemoglobin A1c test remain the favored types of tests for diabetes. Fasting blood glucose tests measure the amount of glucose in the blood at the time of collection. Glucose tolerance tests, which also require fasting, challenge the body to use a glucose load as fuel and graphs the blood sugar response over one to several hours. A1c testing is an average of blood glucose over the past three months. Fasting is not required for the A1c test.
The Facts
Blood sugar tests provide an immediate result. The test, which uses a blood sugar meter to test a drop of blood, is rapid and easy, and can be done at home or at a patient's bedside. In most instances, the fasting status is not considered; results can vary widely. These tests screen for diabetes rather than provide a definitive diagnosis.
Clinicians order blood to be drawn at intervals for a glucose tolerance test, which shows a pattern of blood sugar levels over a certain amount of time. Fasting for this test is difficult and hard on patients, and can result in nausea. Time out of a busy day is required to participate in the test. Inconclusive tests need repeating at the expense of the patient. Pregnant women may be required to take a modified one-hour GTT to detect gestational diabetes.
According to Lab Tests Online, A1c and eAG calculations are used to screen for and diagnose diabetes. The A1c and eAG, which stands for estimated average glucose, does not require a fasting period, but cannot be done on pregnant women, patients who have undergone a recent blood transfusion or those with certain blood disorders.
Considerations
Clinicians decide which of the three types of tests to order based on the status of the patient. The ease of the fasting blood sugar makes the test affordable and a logical first step for screening. The GTT is graphic and measures more than one single instance of blood glucose over time. The A1c must be performed on a chemistry analyzer that is not always available in area laboratories.
Recommendations
Each type of test has merit. The trend in the U.S. is to follow the American Diabetes Association guidelines for the diagnosis of diabetes. As of December 2009, the recommendation is to use the hemoglobin A1C test to diagnose diabetes and identify pre-diabetes. Laboratories across the nation are adding the A1c test to their menu.
Future Considerations
An annual health checkup should include a blood test to detect diabetes. According to the U.S. Centers for Disease Control and Prevention, a quarter of all Americans with diabetes, or about 5.7 million people, do not recognize the signs and symptoms of diabetes. Another estimated 57 million people have pre-diabetes. The only way to know is to be tested. The A1c test is simple, requires only a small blood sample and can be done along with other blood work ordered by a clinician.
