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  • Dr. Scot Lewey
    Dr. Scot Lewey

    Ten Facts About Celiac Disease Genetic Testing

    Reviewed and edited by a celiac disease expert.

      Celiac disease is arguably the most common autoimmune disease. It is very common. It is easily treated. It affects 1/100 people worldwide.


    Caption: Image: CC--Stuart Caie

    Celiac.com 04/16/2019 (originally published 04/24/2008) - Genetic tests for celiac disease and gluten sensitivity are readily available. Testing can be performed on either blood and mouth swab samples. Tests can be done at home and mailed to the lab for analysis.

    A good testing laboratory will provide an accurate prediction of celiac disease risk, and will also provide information about the statistical risk to your children, your likelihood of developing more severe celiac disease, whether one or both of your parents had the risk gene, and for some laboratories, you may determine your risk of gluten sensitivity without celiac disease.

    DQ2 & DQ8 Not the Whole Story

    About 95% of celiacs carry HLA-DQ2; while about 25% carry HLA-DQ8. If any part of the high risk gene patterns DQ2 and DQ8 is missing, then the likelihood of that person getting celiac disease is 99.9% AGAINST. 

    Negative Genetic Test Only Part of the Story

    However, "negative celiac genetic testing” is not sufficient for entirely ruling out celiac disease. To definitively declare negative celiac genetic tests requires the laboratory to test for the presence or absence of the entire HLA DQ genetic pattern, including both alpha and beta subunits.

    The DQ genetic patterns DQ2 and DQ8 have two subunits, but many laboratories only test for the beta subunit. Few labs test for both. This DQ typing is complicated and difficult to understand even by physicians and scientists. I have written an updated detailed review that appears in the Spring 2008 issue of Scott-Free newsletter published by celiac.com.

    No DQ2 & DQ8 Can Still Mean Gluten Problems

    Data collected by Dr. Ken Fine of Enterolab supports the fact that the absence of DQ2 and DQ8 does not exclude the risk of being gluten intolerance or sensitive, though it is now looks likely that one or both of those genetic white blood cell patterns are required for celiac disease or celiac sprue to develop. 

    However, there is a new study that reports that being negative for DQ2 and DQ8 does not completely exclude the possibility of celiac disease, especially in men. 

    Previous studies have documented blood test negative celiac sprue, which is also more common in elderly men with long-standing severe disease. 

    Since DQ2 or DQ8 is almost universally present where tissue transglutaminase and anti-endomysial antibodies are present it is not surprising that individuals without DQ2 or DQ8 with negative blood tests are being reported that meet criteria for celiac disease.

    These new studies are also providing further information that the genetics of celiac 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. Again, in this situation your blood tests may be negative. If you are a woman, the risk for Celiac disease is generally higher than a man, especially if you have received the at risk gene from your father instead of your mother.

    Celiac disease 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 3 or more doctors. Genetic testing can be extremely helpful in determining your risk for celiac disease, potential severity, and risk for family members. Don't be one of those whose diagnosis is missed or needlessly delayed for over a decade. Get tested! Learn about the genetic tests for celiac disease and if necessary educate your doctor about this testing.

    Important Facts About Celiac Disease:

    Genetic Testing Can Determine Celiac Risk

    Celiac genetic tests can be done on blood or a mouth swab sample but your doctor may be unaware of the tests, not know how to order them, or know how to interpret the results.

    Diet Will Not Change Genetic Test Results

    Genetic testing is not affected by diet. You can be eating gluten or on a gluten-free diet. Unlike blood tests for celiac disease antibodies, which require a patient to be eating gluten, genetic tests can be done whether or not the person being tested is eating wheat or gluten. 

    Diagnostic Codes Can Help Secure Insurance Approval

    Many insurance companies pay for celiac genetic testing. Most that pay require pre-authorization. The following diagnostic codes are helpful when requesting insurance coverage: 579.0 (celiac disease); V18.59 (family history of GI disease); and/or V84.89 (genetic susceptibility to disease).

    Some Genetic Labs Perform Limited Tests

    Many laboratories do not perform the all of the necessary components of the test to completely exclude the possible genetic risk of celiac disease and most don't test for or report the other gluten sensitive DQ patterns. Before you accept that have a negative test you need to know if your test included both the alpha and beta subunits of HLA DQ or did they just perform the beta typing.

    Negative Results Can Still Mean Celiac in Rare Cases

    In rare cases, some people, especially men, may have a negative genetic test and still have celiac disease. As with blood tests, men more commonly have negative genetic tests, especially older men with long-standing severe disease.

    DQ Type Can Influence Celiac Risk and Severity

    Both the DQ type, and number of copies you have, matter when determining not only your risk, but also the possible severity of celiac disease. Two copies of DQ2 carries more risk than one copy of DQ8 or only partial DQ2. Even a single copy of DQ2 alpha subunit ("half DQ2 positive") carries risk for celiac disease, but most of the commonly used laboratories for Celiac genetics do not test for or report the presence of this component of the celiac genes.

    Negative DQ2 and DQ8 Can Still Mean Gluten Intolerance

    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 true autoimmune celiac disease.

    No Prescription Needed for Genetic Celiac Testing

    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 $99-300 (www.enterolab.com).

    Genetic Testing Labs for Celiac Disease

    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 therefore their test can miss part of a minor alpha subunit that carries a risk of celiac disease. A negative DQ2 and DQ8 report from these labs may not necessarily be truly negative for the risk of celiac disease.

    Celiac Genetic Testing References and Resources:

     


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    I am using a 'beta only' lab to save money. I've done a lot of research and have found that you can determine most of the alpha units by looking at a chart that tells you which beta and alpha units usually link together. I use the one at the Wikipedia HLA DQ page.

    The only problem I've found with this method is with a DQ2,7 combination. It is important to know if the 7 is a 7.5 or not. If it is, it will combine with the 2 to make a 2.5 trans, which is very high risk. If not, there is still some risk with the DQ2, but much lower. If you do have this combination and you have celiac symptoms, it's probably safe to assume it is 7.5.

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    On 14/06/2008 at 6:49 AM, Guest Richard said:

    Very informative, as a scientist and a celiac I am amazed how complex the genetic marking of celiac disease is. I would even dare to say that it would be easier to look for a gluten-tolerant marker and use the non-presence of this marker as an indicator of gluten related conditions! However, I am even more amazed at the very un-scientific diagnosis process that many 'doctors' follow. Too many people are reporting multiple misdiagnoses and inaccurate testing regimes. As a researcher (astrochemist) I would not trust these 'doctors' in my lab!

    Yes methodology is everything and sadly people dont understand the significance of strict scientific process. Labs take advantage and are too eager to empty the pocketbooks of unsuspecting clients. 

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    Thank you for the interesting article, I was diagnosed by endoscope biopsy aproxametly 15 years ago and have been strict gluten-free with great results ever since. I just had 23and me run my genetic propensity test and it came up negative. Any thoughts? Are they known to be a reliable lab?

    Thank you, Rob in N.CA

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    https://www.ncbi.nlm.nih.gov/pubmed/23085892/

    Human leukocyte antigen DQ2. 2 and celiac disease by Mubarak

    Finding 5.8% of celiac patients (9 patients) not having HLA DQ2.5  or HLA-DQ8 had HLA-DQ2.2.  HLA-DQ2.2 is HLA - DQA1*02:01 and DQB1*02:02. He concluded "Therefore, HLA-DQ2.2 should be included as an important HLA-type related to celiac disease."

    This article was in Journal Pediatric Gastroenterology Nutrition 2013

    My son was very ill for 12 years and we finally figured out from his suffering and symptoms that his father and sister had celiac (100 percent confirmed by endoscopy).  My son was unable to have standard blood tests for celiac because he was on another medication (doctors thought he had a rare childhood autoinflammatory  disease and put him on 3 times a day medication for 3 years).  So genetic testing was performed and I was told he did not have either of the 2 main genes so 99.9 percent he did not have celiac.  Thankfully, I did believe the results especially since a strict gluten-free diet ended all of his medical problems and we figured out to test his dad because of his symptoms.  I continued reading research articles and when I read about HLA Dq2.2 I went immediately to his results and of course he has DQ2. 2. He is now assumed to be a celiac and followed at a celiac center with his sister. 

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  • About Me

    A practicing gastroenterologist in direct patient care but who also participates in teaching medical students and physicians in training as a Clinical Professor of Medicine at Rocky Vista University College of Osteopathic Medicine and at Kansas City University of Medicine and Biosciences. In addition to authoring peer review articles, book chapters and presenting clinical research Dr. Lewey has conducted, he has authored over 50 online articles, numerous blog posts and tweets about digestive and food related issues. As a physician who is a fellow of six professional societies Dr. Lewey serves at a national level on several committees, as a reviewer for journal articles and case reports, a media representative for the AOA Media and ACG on digestive health and disease and has been featured in various print, television, podcast and online media publications about digestive issues. As a expert in digestive diseases Dr. Lewey is also a medical legal consultant and expert witness. Dr. Lewey can be reached at Facebook.com/thefooddoc, on twitter @thefoodgutdoc and at www.thefooddoc.com, and his blog www.thefooddoc.blogspot.com.

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