Wednesday, April 16, 2008
Ten facts you need to know about celiac genetic testing
Celiac disease is a genetic disorder. There are many unanswered questions about the genetics but much has been learned. Here are 10 facts you need to know about celiac disease genetic testing.
10 facts you need to know about celiac disease genetic testing.
1. Genetic testing can help determine your risk as well as your children’s risk for celiac disease.
2. Celiac genetic tests are readily available and can be done on blood or on a sample from a mouth swab but your doctor may unaware of the tests, how to order them, or how to interpret the results.
3. Genetic testing can be done whether you are eating gluten or not eating gluten. Blood tests for celiac disease antibodies however need to be done while eating gluten and become negative within a few weeks of restricting gluten.
4. Your insurance may not pay for the test. Even if your insurance covers the test they likely will require a pre-authorization. When ordering the tests the following diagnostic codes are helpful: 579.0 (Celiac disease); V18.59 (family history of GI disease); and/or V84.89 (genetic susceptibility to disease).
5. Even if your doctor orders celiac genetic testing and your insurance covers it, the laboratory that performs the test may or may not perform the all of the necessary components of the test. So, before you accept that have a negative test you need to know if the test included both the alpha and beta subunits of HLA DQ or just beta typing.
6. If you are a man a negative genetic test may not exclude the possibility of celiac disease anymore than a negative blood test. Men more commonly have negative genetic tests and blood tests.
7. The number and type of at risk genes matter when determining both your risk and the severity of celiac disease. Two copies of DQ2 carries more risk than one copy of DQ8 or only partial DQ2 but even a single copy of DQ2 alpha subunit carries risk for celiac disease though most laboratories do not test for this component of the celiac genes.
8. The absence of at risk genes DQ2 and/or DQ8 does not exclude the possibility of being gluten intolerant or sensitive. You may respond to a gluten free diet even if you don’t have DQ2 or DQ8 or have true autoimmune celiac disease.
9. You can get genetic testing without a doctor’s order and the tests can be done without having blood drawn or insurance authorization if you are willing to pay between $150-400.
10. Laboratories in the U.S. that are known to offer complete alpha and beta subunit genetic testing include Kimball Genetics, Prometheus, and LabCorp. Bonfils, Quest and Enterolab only test for the beta subunit portions and may miss part of a minor alpha subunit that carries a risk of celiac disease.
So, in summary, genetic tests for celiac disease are readily available both on blood and mouth swab samples. These tests can determine the risk of developing celiac disease and predict severity as well provide information regarding family members risk. The absence of any portion of the high risk genetic patterns DQ2 and DQ8 nearly excludes the possibility of celiac disease with an approximate accuracy of 99.9%. However, this requires that both alpha and beta subunit testing is performed. Even then being negative for DQ2 and DQ8 does not completely exclude the possibility of celiac disease, especially in men, and by no means excludes the risk of gluten intolerance or sensitivity.
Recent studies have provided further information that is gender specific. If you are a man, your risk of celiac disease may be higher than a woman if you don’t have the classic genetic patterns and your blood tests may be negative. If you are a woman your risk for celiac disease is generally higher than a man, especially if you have received the at risk gene from your father.
Celiac is arguably the most common autoimmune disease. It is very common. It is easily treated. It affects 1/100 people worldwide. However, most people with celiac disease (>90%) are unaware, undiagnosed or misdiagnosed. Most adults finally diagnosed with celiac disease have suffered at least 10-11 years and have seen more than 3 or more doctors. Don’t be one of those missed or who suffers needlessly. Learn about the genetic testing of celiac disease and if necessary educate your doctor about this testing.
HLA-DQ and Susceptibility to Celiac Disease: Evidence for Gender Differences and Parent-of-Origin Effects. Megiorni F et al. Am Journal Gastroenterol. 2008;103:997-1003
Copyright © 2008, The Food Doc, LLC, All Rights Reserved.
Scot M. Lewey, D.O., FACP, FAAP, FACOP
Dr. Scot Lewey is a digestive disease specialist doctor (board certified gastroenterologist) whose medical practice focuses on digestive and food related illness. Also, known as Dr. Celiac, the Food Doc, Dr. Lewey shares his experiential knowledge for a healthy gut, healthy life on-line. Start learning today from his extensive personal and professional experience. Dr. Lewey is uniquely qualified as an expert and one of the few GI doctors who is also gluten sensitive and dairy sensitive. He has nearly a quarter of century of experience in the diagnosis and treatment of food allergy & intolerance, colitis, Crohn's disease and IBS. He is married to someone who has Celiac disease. He and his family live gluten free in Colorado.
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Posted by The Food Doc, Dr. Scot Lewey on Wednesday, April 16, 2008