Blood tests for gluten | celiac are important for a correct diagnosis. But it is a complicated and controversial area. These are my every practise that I use to make decisions in my Clinic.
Recommended blood tests for Gluten/celiac problems
This includes testing for: celiac (coeliac) disease, gluten sensitivity, gluten intolerance, gluten-related disorders – also known as “Gluten Syndrome“.
Symptoms: if you have ANY symptoms that suggest you could be have celiac disease or could be gluten sensitive, then your next step is to arrange to get your blood tests.
It is important you have these blood tests BEFORE you go gluten free (if possible). So if you can, please keep on eating gluten until you have had your blood tests (you definitely need to be eating gluten if you are going to have an endoscopy for celiac disease).
Gluten blood tests
Currently available blood tests through most medical laboratories (although the choice of test does vary between laboratories):
There are 3 main types of tests:
1) looking for evidence of gut tissue damage.
2) looking for immunological reaction to gluten/gliadin
3) Gene testing for HLA DQ2/ DQ8.
1) TISSUE DAMAGE TESTS: TO LOOK FOR CELIAC DISEASE GUT DAMAGE
Step one is to look for evidence of gut damage: this is to make a diagnosis of celiac (coeliac) disease. There are a number of these “tissue damage” tests are called:
- tTG (tissue TransGlutaminase) – IgA and IgG
- DGP-IgG (Diamidated Gliadin Peptide IgA and IgG)
- EMA (Endomesial Antibodies) – IgA
Celiac disease is defined as the gut damage caused by gluten. When this happens, there is an over-reaction of the immune system in the gut. A harmful immune reaction is generated in the gut tissue. This tissue injury involves inflammatory cells and the production of antibodies. These “tissue damage” tests are very accurate and can detect this damage.
Studies demonstrate that where levels of these antibodies are elevated, more than 95% of patients will be found to have celiac disease.
In other words, if you have a a high tTG, DGP or EMA test, then it is almost certain that you have a diagnosis of celiac disease (the next question is whether you need an endoscopy).
Here is more information about each of these tests.
Please note – the “normal range” of test results varies depending upon the “assay kit” used by the individual lab – there is no universal test kit)
tTG antibody (also called IgA tissue transglutaminase antibody)
The tTG antibody test is a tissue damage test. tTG is a specific antibody made against muscle tissue damage in your small bowel. It is a very sensitive indicator of the small bowel damage that can be caused by the gluten in your diet. High levels of tTG mean that you might have gut damage (celiac disease). It is currently recommended that you confirm the likelihood of gut damage by having a small bowel biopsy (by endoscopy).
Value of tTG: If very high, then celiac disease almost certain. If slightly high, then maybe celiac. Not so reliable in young children.
DGP (Deamidated Gliadin Peptide)
This is a newer type of gliadin test, initially developed and manufactured by Inova Diagnostics. It was developed to more accurately identify people with celiac disease. Eventually, it might overtake the tTG test because it is excellent at finding those people who have gluten gut damage. This test detects an immune response to a very specific fragment of the gluten molecule (this fragment is a short peptide of gliadin – a gliadin peptide). Although this test is excellent for detecting celiac disease (in our Clinic I have found it to be more reliable that the tTG test), it does not detect gluten sensitivity.
It will not pick up the people who have the other symptoms of The Gluten Syndrome. It does not replace the IgG-gliadin test.
Because of its name, it is now frequently confused with the old IgG-gliadin test.
Value of DGP: If both high, then celiac disease is almost certain. Perhaps more reliable than tTG for young children.
EMA (Endomesial Antibodies)
This is an older test and becoming less popular. Nevertheless, it is quite sensitive at detecting the gut tissue damage of celiac disease.
Value of EMA: If positivie, then high chance of celiac disease.
2) GLUTEN TESTS: TO LOOK FOR GLUTEN-SENSITIVITY
Step two is to look for evidence of gluten harm: this is to make the diagnosis of gluten-sensitivity (reactions to gluten without the gut damage).
- Anti gliadin antibody IgG (AGA-IgG) (Also called IgG-gliadin antibody)
- Anti gliadin antibody IgA (AGA-IgA) (Also called IgA-gliadin antibody)
A positive test shows that you have an immune reaction to gluten. This might not be causing symptoms yet. Most gluten-sensitive people have a high IgG-gliadin test.
This test is no longer available in New Zealand
The conflict of the IgG-gliadin test
There is disagreement surrounding the interpretation of the gliadin antibody test. It is found in elevated levels in about 10% of the population. It is a gluten test.
To summarise, beginning in the 1990s, the anti-gliadin IgG antibody test (often referred to as the IgG-gliadin test) was used to verify suspicion of celiac disease. However, it is a poor predictor of celiac disease. By contrast, the “tissue damage” antibodies (see above) are stimulated by bowel tissue damage and are excellent predictors of celiac disease.
There are two opposing schools of thought about the value of IgG-gliadin antibodies:
One school of thought: the medical establishment, represented by the gastroenterologists, have concluded that the gluten blood tests are inaccurate and misleading (in relation to celiac disease). Their total focus has been on identification of the gut damage. They justify their position with the fact that gluten (gliadin) blood tests are poor predictors of who has the tissue damage caused by celiac disease.
Although this is true, they go on to make a serious error of logic. They say that because the gluten tests are not useful in detecting celiac disease, consequently, these gluten tests are not good for anything. This is not correct.
The other point of view held by Dr Rodney Ford
The IgG-gliadin test is a valuable test that can help diagnose gluten sensitivity.
Research shows that the IgG-gliadin antibody test is valuable for detecting people who are reacting adversely to gluten (but who do not have celiac disease). The relationship between patient complaints and high levels of gluten antibodies has been widely investigated. Dr Ford’s research has shown that high levels of gluten antibodies accurately predict a beneficial response to a gluten-free diet. High IgG-gliadin antibody levels are indicative of an immunological reaction to gluten, which can manifest as significant poor health -The Gluten Syndrome.
Frequent questions about gluten/gliadin/celiac blood tests
How common are reactions to gluten?
Gluten intolerance/ sensitivity is very common – it affects more than one in ten people. Some estimate that a third of the population is affected. A recent paper suggests the we are all susceptible to gluten-related disorders. Also, no one can digest gluten. A simple blood test can identify this problem. Please do not go gluten-free without first getting your blood tests. Dr Ford has written extensively about these tests in his book: “The Gluten Syndrome”.
What does the IgG-gliadin test actually measure?
Gliadin is part of the gluten molecule.
The IgG-gliadin test measures your immune response to gliadin.
The IgG-gliadin test measures the levels of ANTIBODY to gluten (also called: AGA-IgG, Anti Gliadin Antibody -IgG).
This test does not actually measure gluten. But it measures your body’s REACTION against gluten.
Why does your body make this IgG-gliadin antibody?
Gliadin is a short protein that your body finds very hard to breakdown in your gut. It is part of the gluten molecule. Because gliadin stays fairly much intact in the bowel, it is easy for it to get through the bowel mucosa in one piece. Then it can start to stimulate the cells of the immune system. These irritated immune cells are stimulated to make antibody molecules against gluten.
Once your immune system starts making this gliadin antibody, your body can continue to produce it for many years, without you ever eating gluten again. However, after a year or two the antibody levels eventually go right down.
Why do the IgG-gliadin test?
The IgG-gliadin test is useful to detect those people who are reacting to gluten. It turns out that one in ten people have a high gliadin antibody level. Most of these people are experiencing symptoms for gluten. Gluten causes a whole host of illnesses, these symptoms are grouped together as The Gluten Syndrome (see The Gluten Syndrome explanation in detail). Gluten reactions are the basis of about a third of all chronic ill-health. In particular, gluten causes gut, skin and nerve/brain disturbances.
Do you have to be eating gluten at the time of the blood test
No. The IgG-gliadin antibody measurement does not detect gluten. It is not a “you have you been eating gluten test”, rather it is a “gluten-reactivity” test. Therefore, you do not have to eating gluten at the time of the blood tests. But the longer that you are on a gluten-free diet, the less accurate the IgG-gliadin tests will be (after years on a gluten-free diet this test will not be useful). If you have been gluten-free for only a few months, then there will be no changes to your blood tests.
It takes between 6-18 months for your IgG-gliadin antibody levels to go down. So, as long as you have not been off gluten for more than 6 months, you can just go ahead and have the blood test.
If you have been off gluten for several years, it may take 2-4 months of eating gluten again before your gluten antibodies go high again.
Where can I get the IgG-gliadin tests?
Unfortunately, many laboratories have abandoned the gliadin antibody test. They say it is “old fashioned” (See the “Dinosaur” article). Most labs now prefer to do the tTG or DGP tests – I think that abandoning the IgG-gliadin test is illogical.
It is important to ask your laboratory BEFORE you get bled, as to whether they can, and will, do the IgG-gliadin antibody test for you. This may incur an additional cost.
This test is no longer available in New Zealand
What if I have a high gliadin tests but have no symptoms?
About 10% of the population have high gliadin antibody levels. Most of these people have some symptoms that are attributable to gluten. However, some have no symptoms (so far). If there is no evidence of gut damage (that is, if you do not have celiac disease), then you can continue to eat gluten (although there is no guarantee that gluten is not causing you subtle harm). Many people now think that it is important to go gluten free if you have high gluten antibodies – these antibodies can cause neurologic harm.
Has the tTG test taken over?
No. The tTG tests does not tell you anything about gluten reactivity. However, the tTG test is useful in detecting people who have celiac disease: they, of course, get better when gluten is removed from their diet.
The tTG tests stands for tissue transglutaminase. It is an antibody test. The tTG is NOT a gluten test. No, the tTG test does not replace the gliadin antibody test. The tTG can ONLY indicate if you have tissue damage (in the gut). However, a high tTG level “infers“ that gluten has damaged the gut – it is a more accurate indicator of gut damage than endoscopy. The tTG, is not a perfect test, especially in children.
Has the DGP test taken over?
One of the newest tests to detect the gut gamage of celiac disease is the Deamidated Gliadin Peptide (DGP) antibody test. For detailed information on this tests follow this link: Gliadin antibody confusion: same name – different test
Does my doctor know how to interpret the results?
Probably, your doctor is not familiar with the interpretation of the IgG-gliadin tests. In my experience, most doctors have been taught to ignore this gliadin test. Most doctors at this stage still do not recognise that gluten can cause a lot more disease than just celiac disease.
The medical focus has been on the tTG test (for tissue damage). The majority of my patients who have had the IgG-gliadin tests by their GPs have been told that their tests were “normal” or “nothing to worry about” or “or just a touch of reaction” or “not coeliac, so nothing to do about it.
I suggest that you actually look at the tests results yourself. The eClinic can help you interpret them as well.
If you are already gluten free
“Do I have to be eating gluten at the time of my blood tests?”
The answer depends upon which tests you are going to get. However, if you have been strictly gluten-free for the last 2 years or more, your blood tests should now be back to near normal (although some tests (IgG-gliadin and tTG) can take 3 or more years to get back to normal levels).
IgG-gliadin antibody levels. The blood tests for gluten (IgG-gliadin antibody) take about 6 months or more to change once you go gluten-free. So if you have only been gluten-free for a few weeks or months, then it is okay to get your blood tests. You do not have to go back and eat more gluten.
DGP levels can go down within a few months of going gluten-free.
tTG levels take a few years to go down on a gluten-free diet.
Use the eClinic for help with the interpretation
Often GPs are unfamiliar with the gliadin test (it is not offered in all laboratories), so they subsequently are unsure of the interpretation. So if you enter the blood test results into the “TEST results” section of the eClinic, you will get an accurate interpretation.
The ebook that tells you much more about this topic is: The Gluten Syndrome.