Testing Positive for the Celiac Disease Gene

With the advent of advanced molecular genetic testing, doctors are now more than ever able to identify chromosomal disorders either directly or indirectly linked to a disease. One of these is celiac disease.

Unlike some conditions in which a positive result is directly associated with the symptoms of a disease, a positive result for a celiac gene test suggests the likelihood—rather than certainty—of disease.

In most cases, the likelihood will be small.

Identifying the Celiac Genes

Two chromosomal mutations, known as HLA-DQ2 and HLA-DQ8, are commonly associated with celiac disease.

By definition, HLA (human leukocyte antigen) is a cellular protein which triggers an immune response. With celiac disease, aberrations in the HLA coding can cause the immune system to go haywire in the presence of gluten and attack cells of the small intestine.

Despite the fact that HLA-DQ2 and HLA-DQ8 are both linked to this effect, having the mutation doesn't necessarily mean that you'll get the disease. In fact, as many as 40 percent of the U.S. population have these mutations, mostly in people of European descent.

Of those who do carry the mutation, only around one percent to four percent will go on to develop the disease in their adult years. All told, around one of every 100 people in the U.S. will get celiac disease in one form or another with symptoms ranging from serious to virtually non-existent.

What Happens if You Test Positive

Testing positive for either HLA-DQ2 or HLA-DQ8 does not mean you have to change your eating habits unless you have symptoms of the disease (including damage to the villi that line the small intestines). The test will simply tell you that you have a propensity for the disease, nothing more.

With that being said, most celiac specialists will advise you and your family to be regularly monitored in the event one or more of you eventually become symptomatic.

This is because the HLA mutations are passed from parent to child, with some children inheriting two copies of the mutation (one from each parent) while others only inherently one. Clearly, those inheriting two are at greatest risk.

On the other hand, if you have symptoms and all other test results are negative, a positive HLA test may justify a trial period during which you stop gluten to see if your symptoms improve.

A Word From Verywell

People who suspect they have celiac disease will often preemptively start a gluten-free diet to see if their condition improves. While this is perfectly fine and won't cause any harm, starting preemptively may impede your ability to get an accurate diagnosis if you do decide to undergo testing.

This is because a standard celiac blood panel will look for specific antibodies to gluten in your bloodstream, while an endoscopic exam will search for visual evidence of damage in the small intestine. Without exposure to gluten, the tests are less able to identify characteristics of the disease and may end up returning a false negative result.

When looking for an accurate diagnosis, you must be exposed to gluten. A genetic test can only suggest the likelihood of disease rather than offer a definitive diagnosis.

Source:

Wessels, M.; Vriezinga, S.; Koletzko, S. et al. "Impact on parents of HLA-DQ2/DQ8 genotyping in healthy children from coeliac families." Eur J Hum Genet. 2015; 23, 405-88. DOI: 10.1038/ejhg.2014.113.