Question 1

How accurate is the HLA-DQ2/DQ8 genetic test for celiac disease?

Accepted Answer

The test has a high negative predictive value but a low positive predictive value. This means if the test is negative, you can be very confident you don't have celiac disease risk, but a positive test doesn't guarantee you will develop the disease. More than 95% of celiac disease patients are positive for DQ2, half DQ2, or DQ8, but many individuals with these genetic results do not develop celiac disease. The test is most valuable for ruling out celiac disease rather than confirming it.

Question 2

Can I take this test if I'm already on a gluten-free diet?

Accepted Answer

Yes, this is one of the major advantages of genetic testing. Unlike antibody tests for celiac disease, genetic testing is not affected by gluten intake and can be performed regardless of diet. Since this test examines your genetic makeup, which doesn't change over time, it provides accurate results whether you're eating gluten or following a gluten-free diet. This makes it particularly useful for people who have already started eliminating gluten from their diet.

Question 3

What's the difference between this genetic test and other celiac disease tests?

Accepted Answer

Unlike antibody tests that detect immune responses to gluten exposure, this genetic test examines your DNA for inherited risk factors. Antibody tests require ongoing gluten consumption to be accurate and can become negative after starting a gluten-free diet. The genetic test provides permanent information about your risk since genetics don't change. However, genetic testing alone cannot diagnose active celiac disease --- it only indicates predisposition or rules out the possibility entirely.

Question 4

If my test is positive, does that mean I have celiac disease?

Accepted Answer

No, a positive genetic test does not confirm celiac disease. These genetic markers are necessary but not sufficient for disease development. While the presence of HLA-DQ2 or HLA-DQ8 increases risk, most people with these variants never develop celiac disease. About 30% of the healthy population has genetics compatible with celiac disease, yet only 1% of the population develops the disease. Additional testing with antibody tests and possibly intestinal biopsy would be needed to confirm active celiac disease.

Question 5

Should family members get tested if someone in my family has celiac disease?

Accepted Answer

Between 10% and 30% of first-degree relatives of a celiac person also have genetic predisposition compatible with celiac disease, though this only means they may develop the disease, not that they will. The risk for developing celiac disease increases significantly when there is a first-degree relative with celiac disease, with risk approaching 40% for siblings with the same HLA genotype as a patient with celiac disease. Genetic testing can help family members understand their risk and guide decisions about monitoring and additional testing.

Celiac Disease Genetic Test (HLA-DQ2/DQ8)