Sunday, October 3, 2010

What is the celiac gene?

How common is this gene?

People with coeliac disease usually have the coeliac gene (over 95% of coeliac carry this gene). This gene has been characterised as HLA type DQ2 or DQ8. If these genes are detected, then it means that you have the genetic possibility of developing coeliac disease, if you continue eating gluten.
It does not mean that you have coeliac disease.

Positive tests

However, in population studies, about 1 in 4 people (25%) have these genes. As coeliac disease is found in 1 in 100 people, if you carry the “coeliac gene” you have a 1-in-25 chance of getting coeliac disease. Therefore, this DQ2/DQ8 gene is only indicative of the possibility of developing coeliac disease.

Negative tests

If the gene test is negative, that means that it is very unlikely that you would develop coeliac disease (in a group of 100 coeliacs, between 3 and 5% will not have the coeliac gene).

Coeliac disease vs gluten-sensitivity

In coeliac disease, there is damage to the small bowel mucosa by the toxic inflammatory affects of gluten on the bowel. This bowel damage is associated with a high tTG antibody (and high DGP antibodies). On small bowel biopsy (by endoscopy) abnormal tissue is found which is called villous atrophy. In gluten-sensitivity, there is no bowel damage. But there are a multitude of symptoms that can be caused by gluten. Gluten-sensitivity (the Gluten Syndrome) is not restricted to people with the coeliac gene, although it is found more often in people with a positive gene test.

Value of HLA tests

The coeliac gene is a useful test to decide who should go ahead to have a small bowel biopsy. Also, to identify those people who need ongoing surveillance for developing coeliac disease. If you do have coeliac disease this means that you need to be gluten free life-long. On the other hand, with gluten-sensitivity, gluten can be eaten to tolerance (this is a debatable point). Unfortunately, most people who are gluten-sensitive are extremely sensitive to gluten: even trace amounts of gluten causing symptoms.

I hope this helps you understand the place of this “gene” test.

(It is a lot more complex than this – but this is the most simple answer)

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