Genetic tests for celiac disease look for genes called HLA-DQ2 and HLA-DQ8. Most people with celiac disease have one or both of these genes, but their presence doesn’t necessarily mean you have celiac disease. It only means it’s possible for you to develop it.
This article looks at genetic testing for celiac disease, why it’s done, and what the process is. It also helps you understand how the results are interpreted.
What Is Celiac Disease?
In people who have certain genes, eating gluten can trigger symptoms of celiac disease. Gluten is a protein found in the grains of wheat, barley, and rye.
Celiac disease is an autoimmune condition. Autoimmune conditions cause your immune system to mistake a normal part of your body for an invader. When you have celiac disease, your white blood cells attack the lining of your small intestine.
If your healthcare provider suspects celiac disease, they will first do a physical exam and take your medical history. Blood tests that look for high levels of certain antibodies can help confirm the diagnosis.
Your healthcare provider may also order a biopsy. This is a procedure where a small sample of cells is taken from your small intestine.
A biopsy that tests for celiac disease is done during an upper endoscopy. During this test, a healthcare provider views the upper part of your digestive system with a camera attached to a long, flexible tube.
Your doctor may also order a genetic test to help confirm celiac or rule it out.
Genes Involved in Celiac
The genes that predispose you to celiac disease are members of the HLA complex of genes located on chromosome 6. Specifically, they’re known as DQ genes. Everyone gets two copies of a DQ gene, one from their mother and one from their father.
There are many different types of DQ genes, but only a few are associated with celiac disease. These include:
HLA-DQ2HLA-DQ8HLA-DQ7
Studies have shown that about 96% of those diagnosed by biopsy carry either DQ2, DQ8, or both.
HLA-DQ2
HLA-DQ2 is by far the most common celiac-related gene found in the general population. Between 90 and 95% of people with celiac disease carry this gene.
HLA-DQ8
HLA-DQ8 is carried by significantly fewer people with celiac disease. It is found in between 2.5 and 5% of celiac patients.
HLA-DQ7
Because there is a small percentage of celiac patients who do not carry either HLA-DQ2 or HLA-DQ8, researchers are looking for other genes that may predispose people to developing celiac disease.
At least one study has suggested that the HLA-DQ7 gene may also predispose you to celiac disease. In that study, 2% of people with a biopsy-proven celiac disease carried HLA-DQ7, but not DQ2 or DQ8. There’s some controversy, however, about this gene and whether it actually predisposes you to celiac disease. Genetic testing in the U.S. does not currently recognize DQ7 as a “celiac disease gene.”
Research indicates you don’t need to carry HLA-DQ2 or HLA-DQ8 in order to develop non-celiac gluten sensitivity. There may be additional HLA-DQ genes involved in gluten sensitivity.
Reasons for Celiac Gene Testing
If you have one copy of the DQ2 or DQ8 gene, you have a much greater risk of developing celiac disease. Since you get one DQ gene from your mother and one from your father, it’s also possible for you to have two copies of DQ2 or DQ8. There is some evidence that carrying two copies of one of these genes may increase your risk even more. Knowing which genes you carry, if any, can help you understand what your risk is.
Not everyone who has celiac disease genes will develop the celiac disease. Up to 30% of the population has DQ2, DQ8, or both. Only around 1% of the general population has celiac disease, however.
The genetic test can only tell your healthcare provider if you might have celiac disease. It can also be used to rule out celiac disease if the cause of your symptoms isn’t clear.
Celiac Gene Testing Process
Testing for celiac disease genes isn’t invasive. You’ll either:
Provide a sample of your bloodUse a swab to collect a few of the cells from inside your cheekUse a syringe or a vial to gather saliva
Your blood, cheek cells, or saliva will be analyzed by a laboratory. All of these methods produce equally accurate results.
Most people have genetic testing performed along with other tests ordered by their healthcare provider. It is also possible to order the test from a genetic testing company like Enterolab or 23andMe.com. Enterolab also performs gluten sensitivity testing.
Enterolab will analyze your genes and tell you which HLA-DQ genes you carry, if any. Cells are collected with a cheek swab, so there’s no blood draw involved. Once you ship off your sample, the results are emailed to you within about three weeks.
With 23andMe.com, meanwhile, you’ll spit into a vial and send the vial to be tested. Results are available electronically in about three to four weeks.
How to Prepare
You don’t need to do anything special to prepare for a genetic test. Unlike with conventional celiac testing, you do not need to be eating gluten for the results to be accurate. If you are having a blood test, you also will not need to fast ahead of time.
Cost
Genetic testing may not be covered by your insurance provider. Many insurers have different policies regarding different types of genetic testing, however. If you’re not sure, call your insurance provider and make sure it’s covered before scheduling your test.
The Enterolab genetic test costs around $150, paid at the time you place the order. 23andMe provides celiac disease gene testing through its “Health and Ancestry” option, which costs around $200. With 23andMe, your report also will provide detailed information on your ancestry and data on genetic relatives.
Interpreting Test Results
Depending on where you get your test, results could take anywhere from a few days to a few weeks. Many labs provide your results electronically.
Not everyone who carries a celiac gene is diagnosed with celiac disease. This means a positive genetic test does not equal a diagnosis. A positive celiac disease genetic test just puts you in what healthcare providers consider a “high-risk” group for celiac disease.
The gene tests are mainly useful to rule out celiac disease when celiac-like symptoms are present. In some cases, a person might have celiac test results that aren’t clear-cut. When this happens, a gene test can help confirm or rule out celiac.
If someone in your family has been diagnosed with celiac, your healthcare provider may recommend celiac testing for you, too. This can help rule out celiac disease or alert you to any predisposition you might have.
A gene test may also be helpful in suggesting celiac disease in someone who’s already on a gluten-free diet. Sometimes, a patient may stop eating gluten to improve their symptoms, and then decide to be tested afterward. In this case they would either have to attempt a gluten challenge, or undergo genetic testing.
The gene test can only tell you if you have the potential to develop celiac disease. Still, even though genetic testing can’t provide absolute answers, many people prefer it to a gluten challenge.
Summary
Celiac disease is associated with two distinct genes: HLA-DQ2 and HLA-DQ8. Genetic testing can tell you if you carry one or both of these genes.
Genetic testing can’t, however, tell you if you have celiac disease. It can only tell you if you’re predisposed to it. Many people who carry these genes never develop celiac disease.
A Word From Verywell
There’s much we don’t yet know about celiac disease. It’s not clear why some people with celiac disease genes develop it while others do not. Celiac disease genetic testing can help determine the risk for this condition in family members, and in cases that aren’t completely clear-cut.
If you have symptoms of celiac disease, talk to your healthcare provider. Testing, both genetic and otherwise, can help you find answers and ensure your condition is managed correctly.
