Genetic Testing for Type 2
Diabetes risk factors add up: the more diabetes risk factors you have, the greater your chance of developing diabetes. Like all common diseases, rarely is one risk factor alone responsible for causing the disease.
In April 2007, a genetic testing company released a new genetic test designed to detect the first, confirmed genetic type 2 diabetes risk factor (marker), called deCODE T2™. This test looks for a marker in the TCF7L2 gene that has been proven to show an increased diabetes risk in over 20 different populations and ethnic groups around the world.
People who test positive for the TCF7L2 marker are twice as likely to develop diabetes than people who do not have the risk marker. About 1 in 5 people with diabetes (18%) carry the risk marker compared to about 1 in 10 (8-11%) of the general population.
For people who do test positive, studies show that preventive measures – diet, exercise and/or medication – can be especially important in lowering your overall risk and helping to prevent diabetes.
There is additional research under way which suggests that, for people who test positive, certain medications may be more effective at preventing and treating diabetes than others.
Should You Consider Testing?
If you have type 2 diabetes or any of the following diabetes risk factors, you might want to consider testing. Depending on your reason for testing, results can provide you with important information that might help your doctor with treatment decisions. They may also provide you with the motivation to make preventive lifestyle changes.
- You are overweight
- Your doctor has told you that you are at increased risk for developing diabetes
- You have had abnormal results on tests that measure blood sugar
- You are have prediabetes
If you have a family history of diabetes, the TCF7L2 test may provide insight into a specific genetic risk that may be contributing to your family history. It is important to realize that there may be other genetic risks in your family for which DNA testing is not currently available. Researchers continue to study other hereditary causes of diabetes, including inherited obesity.
If you have other risk factors for diabetes, listed below, this test might motivate you to make changes. Diabetes risk factors add up. This test may be useful if having a positive result would motivate you to make preventive lifestyle changes.
• Poor exercise regimen
• High blood pressure
• High triglycerides
• High cholesterol
• History of gestational diabetes
• Ethnic Risk: African American, Latino, Asian American, Pacific Islander, Native American
(Note: The TCF7L2 test does not diagnose diabetes — it tells you about your risk for developing diabetes. Diabetes is diagnosed by other tests, including fasting blood glucose (sugar) tests, urine glucose tests, and glucose tolerance tests.)
What You Can Do With Test Results
If you test positive, you can work with your healthcare team to decide how best to lower your risk for diabetes.
- If you have a positive result and have prediabetes, an NIH-sponsored clinical trial has shown that weight loss, exercise, and (in some cases) medication can overcome the increased risk for diabetes that this gene marker carries.
- If you have a positive result and have diabetes, this test result can partly explain your diabetes. It can also help your doctor to determine the most effective treatment.
- If you have a positive result and do not have diabetes or prediabetes, this result indicates that you are about twice as likely to develop diabetes as someone with a negative test result. For many people in this situation, this test result gives them extra motivation to pursue a healthy lifestyle to reduce their risk and to get regular screening for diabetes.
If you test negative, it simply means that you do not have this particular genetic risk. A negative result does not mean that you will never develop diabetes. Remember, diabetes may be caused by a number of factors including lifestyle, environmental, and other genetic factors that have not yet been identified.
READ MORE: TCF7L2: Frequently Asked Questions
1 - DNA Direct. "Diabetes Risk (deCODE T2™)", www.dnadirect.com (Accessed 11/5/07.)
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