Coeliac disease and Gluten-intolerance in Bloating and IBS

This is a slightly complicated area but definitely worthwhile knowing about about, given all the views about gluten out there on social media.

22.1 Coeliac disease

Coeliac disease, to keep things simple, may be considered an Allergy (so, involves the immune system) to gluten, a protein found in wheat, barley and rye and gives bread its nice, chewy and moist texture.

The Symptoms of Coeliac disease are many and include Bloating, Diarrhoea, cramps or even, bizarrely, Constipation. Many, many people with IBS who have these symptoms say they feel better when they avoid gluten. This does not mean that they have Coeliac disease, but rather, it is much more likely that they have an "Intolerance" - the immune system is NOT involved.

Coeliac disease has a major distinctive feature. The lining of the gut in a person with untreated coeliac disease does not have the microscopic finger-like "fronds" called villi through which we absorb nutrients. This is because they have been damaged by the immune system. On the other hand, the gut lining of people with IBS who have Gluten intolerance with similar symptoms and who feel better when they avoid gluten, is completely normal.

Something to highlight straight away: we can do tests for Coeliac disease, but, there are NO tests for Gluten-intolerance.

The problem with tests to see whether we have Coeliac disease or not is that they look for the body's reaction to gluten. So, if we are not eating enough gluten (two slices of bread daily for at least six weeks), then the tests may normal, when in fact Coeliac disease is present. That goes especially for blood tests but if you were to have an endoscopy with taking samples of the small bowel lining, then probably two weeks on gluten should bring about enough change.

22.1.1 Blood tests for Coeliac disease
There are two blood tests that look for antibodies (molecules produced by the immune system to target something that it is threatened by- so commonly viruses or bacteria. They are positive in the vast majority of people with Coeliac disease, but they are negative in people with IBS:

• Anti-endomysial antibodies

• Anti-tissue Transglutaminase (TTG) antibodies (the most accurate one)

These tests are very accurate but, it is essential that gluten has been eaten every day for at least six weeks before blood tests are done otherwise the test result will be negative (even when the person does actually have coeliac disease). About two slices of ordinary bread each day is considered enough. No gluten, no test!

Just mention, there is an older blood test that looks for "alpha-gliaden antibodies". This is a "bad" test as it may often be positive for no good reason. Many labs no longer bother doing it as it causes more confusion than anything with these "false-positives". Even the newer "de-aminated gliaden" blood test is not that accurate.

One last thing about these blood antibody tests- sorry! There are different families of antibodies. The main ones are called A, G and M. The antibody type looked for mainly with coeliac blood testing is the "A" type.

Now, some of us have naturally low levels of A-type antibodies, so you cant really go looking for A type antibodies to gluten if we don't make A-type antibodies to start with! For this reason, laboratories should routinely include a "total" IgA level with the coeliac blood results, so doctors can tell if the results are valid or might be a "false" negative. If it's not on the results sheet, it needs to be done.

If you have coeliac disease and go on a strict gluten free diet, then the blood tests will turn negative after a few months (no gluten-no reaction, again)

We'll talk about gene blood tests a little later.

22.1.2 Small bowel biopsy for Coeliac disease
Another, more invasive way to diagnose Coeliac disease is to do an endoscopy and take some biopsies (samples) from the duodenum which anatomically comes after the stomach and is the first bit of the Small intestine. Pretty quick and painless test, though obviously more invasive than a blood test.

The biopsies are sent to a lab for microscopic examination where the length of the villi (finger-shaped absorbing part of the small bowel cells) as well as the number of lymphocytes (immune cells) are assessed. A scoring system (Marsh score) is used to decide whether it looks like Coeliac disease or not.

If you have a positive blood test for Coeliac disease (even if it is the very accurate TTG test), the doctor will always want to confirm it with doing an endoscopy and taking these biopsies. You need more than one piece of proof ideally to make what is really a life-long diagnosis.

If someone has Coeliac disease and goes onto a gluten free diet, then their small bowel biopsies will go back to being normal. This makes sense as the immune system in the gut is no longer reacting against anything. It can take a long time for this change back to normal to take place- maybe even up to two years, although symptoms get better very quickly.

One thing to mention again is that if you want to do a test to check for Coeliac disease and have been on a gluten free diet, you will just have to go back on a “normal” diet, sorry! The test to do to minimize the length of time on that normal diet would be endoscopy with biopsy (about two weeks will do, but some hospitals may ask for longer).

To summarize:

Negative anti-endomysial antibodies or TTG = Don't have coeliac disease (or, have coeliac but not eating any gluten, or naturally low levels of IgA).

Normal small bowel biopsies = either no coeliac disease or have coeliac but not eating any gluten.

22.1.3 Testing for Coeliac disease when on a gluten-free diet
The standard tests (blood tests or even a small bowel biopsy) cannot be used if we are on a fully gluten-free diet, as any "damage" may have healed following exclusion of gluten from the diet.

So, a common question: "How can I be checked for coeliac disease if I have been avoiding gluten for months? I really don’t want to go back to it for six weeks because it makes me feel awful."

There is no easy or full and definite answer to this problem. If you are not eating gluten nobody can tell whether you have Coleiac disease or not- full stop! But we can turn the question on its head and do a test to see if it is very unlikely that you could have Coeliac disease. This is done with a genetic blood test.

Everyone with coeliac disease has at least one of the genes HLA DQ2 or HLA DQ8. So, if your blood test were negative for both, you don't have a genetic risk for Coeliac disease. A valuable result that is easy to interpret.

However, if the test for either DQ2/DQ8 were positive, that is something very, very different. It is not a valuable result- it tells us nothing useful because many people around the world have these genes but will never, ever develop Coeliac disease. Another way of putting this: the Irish are more likely than most races to get Coeliac disease but, just because you are Irish, doesn't mean that you have Coeliac disease.

To summarize, as this is complicated:

• Blood test NEGATIVE for DQ2 and DQ8: extremely unlikely that you could have coeliac

• Blood test POSITIVE for either DQ2 or DQ8: maybe you do, or maybe you don't have coeliac disease! It does not and cannot diagnose coeliac disease.

So, the only result that is helpful is a NEGATIVE one.

The HLA DQ2 / DQ8 blood test is widely available but is not that often used as it is expensive.

22.2 Non-Coeliac disease Gluten sensitivity in Bloating and IBS
Even the smallest amount of gluten causes damage to the gut lining of people with Coeliac disease. The amount that can cause damage is about 50mg. To give you a measure of how much that is, a slice of bread has about 1600mg in it. This damage does not happen in those of us with IBS who have might have what is called "Non-Coeliac Gluten Sensitivity".

For those of us with IBS who have Non-Coeliac Gluten Sensitivity, it is a matter of the gut not being able to tolerate wheat and other major sources of gluten.

Again, the response to gluten does not involve the immune system.

It is important also to highlight that "Intolerance" to gluten is a very real condition and not just in the mind. A study has shown that when someone with IBS feels better by excluding gluten from their diet and is then given "hidden" gluten (without telling them) their symptoms will flare-up again.

Another thing to mention is that foods like wheat also contain other things that can upset the tummy - for example "fructans". These other substances might actually be the culprit causing symptoms, rather than the gluten itself. Scientists have looked hard to find out if gluten causes any "inflammation" in the gut cells of those of us with IBS, but all the results so far have been negative.

22.2.1 Tests for Gluten Intolerance
There is no test for gluten Intolerance (often called: non-coeliac gluten sensitivity) but, it has been suggested that those of us with a positive alpha-gliadin blood test (this is an older, less good test for coeliac disease), when the rest of the coeliac disease blood screen is negative, might be more likely to be sensitive to gluten, but the evidence for this link is not very convincing.

Also, scientists think that people with a positive DQ2 or DQ8 blood test, but with a NEGATIVE coeliac antibody screen on a normal diet (think about that one for a moment!) are more likely to have an Intolerance to gluten. The DQ2/DQ8 blood test is expensive and the results in relation to IBS are not fully understood, so it is not a standard test for gluten intolerance.

22.3 Allergy to wheat with Bloating and IBS
Now this really is going to confuse things! We can have Coeliac disease, we can have Gluten intolerance and extremely rarely, some people can have an allergy to just wheat. It causes much the same tummy symptoms as the other two. Like the gluten-sensitivity, the blood tests for Coeliac disease are negative, but there is a "skin prick IgE" test that is used to diagnose this Allergy. Again, it is very rare and is only mentioned for the sake of being complete. To keep life simple, forget about it!