Celiac HLA-DQ2/DQ8 Genotyping

What is celiac HLA-DQ2/DQ8 genotyping?

Celiac disease is a chronic condition in which the immune system develops a reaction that damages the small intestine in response to gluten, a protein found in wheat, barley and rye. It may present with symptoms such as diarrhea, bloating, weight loss and anemia, but in some people it may be noticed only through iron deficiency or osteoporosis, without any obvious complaints. Treatment relies on removing gluten-containing foods from the diet for life; for this reason, an accurate diagnosis is also important for avoiding unnecessary dietary restrictions.

For celiac disease to develop, certain tissue-type (HLA) genes must be present. Almost all patients carry at least one of the gene types known as HLA-DQ2 and/or HLA-DQ8. This test uses molecular methods to look for these gene types in DNA extracted from blood. However, these genes are common in the general population, and most people who carry them never develop celiac disease; for this reason, the test is a predisposition test.

When is the celiac HLA-DQ2/DQ8 test ordered?

Celiac disease is first investigated with blood tests such as tissue transglutaminase antibodies and, when considered necessary, confirmed with a small intestine biopsy. HLA genotyping does not replace these tests; it is ordered on a doctor's recommendation as a guide when the diagnosis remains unclear or the other tests cannot be interpreted.

• Antibody test and biopsy results that do not agree with each other
• People who started a gluten-free diet before being diagnosed and cannot go back to eating gluten
• Assessing risk in people who have a first-degree relative with celiac disease
• Conditions with an increased risk of celiac disease, such as type 1 diabetes, autoimmune thyroid disease, Down syndrome or Turner syndrome
• Unclear cases in which celiac disease needs to be ruled out

The test's greatest strength is that a negative result very likely rules out celiac disease. This makes it easier for the doctor to assess whether some people in risk groups need repeated antibody screening. With a positive result, follow-up and additional tests are planned by the doctor.

How do you prepare for the celiac HLA-DQ2/DQ8 test?

No fasting is needed for this test, and the blood sample can be given at any time of day. Unlike antibody tests, the genetic test is not affected by gluten intake; it can be done while you are on a gluten-free diet. This makes the test particularly useful for people who started the diet before being diagnosed. The blood sample is taken from the arm, and the procedure takes a few minutes. The medications you take do not affect the result either.

Genetic tests are performed with informed consent; if assessing family members is being considered, genetic counseling is recommended. If you have had a bone marrow transplant, mention this. Our nurse collects your blood sample at your home or workplace; if your doctor has also ordered antibody tests, samples for these can be given during the same blood draw.

How are celiac HLA-DQ2/DQ8 results interpreted?

The report states whether the gene types associated with HLA-DQ2 and HLA-DQ8 are carried and in which combination. If none of these types is detected, the likelihood of having celiac disease or developing it later is very low. With such a result, if your complaints continue, your doctor will look into other causes. Because genetic makeup does not change, this test usually does not need to be repeated.

A positive result, on the other hand, shows only a genetic predisposition and does not diagnose celiac disease. Because most people who carry these genes do not develop the disease, a positive result requires antibody tests and, if needed, a biopsy for diagnosis. The gene combination carried can give additional information about the degree of risk. Your result should be evaluated by your doctor together with your symptoms and other test results.