Also known as: Coeliac disease tests / gluten-sensitive enteropathy tests
Name:
Related tests: Albumin, Autoantibodies, Calcium, Full blood count, Total protein, Vitamin B12, Vitamin D, CMP, Vitamin E
Why get tested?
To help establish whether you have coeliac disease and to monitor adherence to and the effectiveness of a gluten-free diet.
When to get tested?
When you have symptoms suggesting coeliac disease, such as chronic diarrhoea, abdominal pain, anaemia and weight loss. When a child is persistently irritable or is growing more slowly than normal. Occasionally to monitor the treatment of coeliac disease.
Sample required?
A blood sample taken from a vein in the arm
What is being measured?
Coeliac disease tests are a group of tests developed to help diagnose coeliac disease and a few other gluten-sensitive conditions. These tests detect autoantibodies that the body produces as part of an immune response to dietary proteins (gluten and gliadin) found in wheat, rye and barley. These autoantibodies cause inflammation of the intestine and damage to the intestinal lining. This causes symptoms associated with malnutrition and malabsorption, such as diarrhoea, weakness, weight loss, abdominal pain, bloating, tiredness, mouth ulcers, a tendency to bleed, bone and joint pain, and anaemia. Adults may also have depression and a general feeling of being unwell, while children are often irritable and may have delayed growth and development.
In the past the only way to diagnose coeliac disease was with a biopsy of the small intestine. While this microscopic examination is still considered the gold standard and is still used to confirm the diagnosis, the availability of less invasive blood tests to screen for coeliac disease has reduced the number of biopsies. The available blood autoantibody tests include:
Tissue transglutaminase antibodies (tTG), IgA: tissue transglutaminase is an enzyme responsible for cross-linking certain proteins. It has been identified as the antigen the body responds to when it produces anti-EMA antibodies. The gliadin in wheat triggers the development of tTG antibodies. Although the name of this autoantibody includes the word “tissue”, the test is carried out on blood, not tissue.
Endomysial antibodies (EMA), IgA: the endomysium is the thin layer of connective tissue covering individual muscle fibres. Endomysial antibodies develop in reaction to ongoing damage to the intestinal lining. Almost 100% of patients with active coeliac disease and 70% of patients with dermatitis herpetiformis (another gluten-sensitive enteropathy that causes an intensely itchy, burning skin rash) will have IgA anti-EMA antibodies. Anti-tTG and anti-EMA antibodies measure the same tissue damage.
Anti-gliadin antibodies (AGA), IgG and IgA: gliadin is the part of the gluten protein found in wheat (similar proteins are found in rye, barley and oats). AGA is an autoantibody against gliadin. It is produced by sensitive people when they are exposed to gluten over a period of time.
Anti-reticulin antibodies (ARA), IgA: anti-ARA are not requested as often as they once were, as they are not as specific or sensitive as the other autoantibodies. They are found in about 60% of patients with coeliac disease and about 25% of patients with dermatitis herpetiformis. When used, ARA are requested together with other coeliac disease tests to help make the diagnosis.
Each available blood test for coeliac disease measures the amount of a particular autoantibody in the blood and is available in both IgG and IgA versions. IgG and IgA are two of the five classes of antibody protein that the immune system produces in response to a trigger.
Although both the IgG and IgA forms of each autoantibody are present in the blood, they are not equally specific for coeliac disease. In general, IgA tends to be more specific, and in some cases is used almost exclusively. IgG may be requested either to complement the IgA test and/or because someone has IgA deficiency. This happens in about 2% of people with coeliac disease and can lead to some false negative results.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
How is it used?
When is it requested?
What does the test mean?
Is there anything else I should know?
How is it used?
Coeliac disease tests are used to screen for and help diagnose coeliac disease and some other gluten-sensitive conditions (such as dermatitis herpetiformis). They are usually requested for patients with symptoms suggesting coeliac disease, but may also be requested to help rule out coeliac disease as a cause of conditions such as anaemia and abdominal pain. Since people with coeliac disease may also have conditions such as lactose intolerance, coeliac tests may be done together with other intolerance and allergy tests.
Coeliac testing is sometimes requested to screen for coeliac disease without symptoms in people who have relatives with coeliac disease (about 10% of people with an affected relative will develop it) and/or in people who have another autoimmune disease (people with an autoimmune disease often have more than one).
The doctor may request one or more coeliac tests, together with tests to assess the patient’s condition and the extent of malnutrition and malabsorption. There are four autoantibodies linked to coeliac disease that can be measured. The doctor will often request tissue transglutaminase antibodies (tTG), IgA, first of all to screen for coeliac disease. The doctor may carry out an intestinal biopsy to confirm that the intestine is damaged. If anti-tTG is negative but the doctor still suspects coeliac disease, further tests may be requested, including:
Anti-gliadin antibodies (AGA), IgG and IgA. These tests are often useful when testing a child without symptoms, but they are found in fewer cases of coeliac disease than anti-tTG and can also be positive in other conditions. AGA IgG and IgA are often requested together so that their results can be compared. If one is positive, both should be, unless the patient has IgA deficiency. They can be used to monitor adherence to the diet.
Endomysial antibodies (EMA), IgA. This test is requested together with the anti-tTG test, as both measure the autoantibodies that cause the tissue damage associated with coeliac disease. Anti-EMA is still requested by many doctors and may be used to monitor adherence to the diet.
Anti-reticulin antibodies (ARA), IgA. Anti-ARA is not requested as often as it once was because it is not as specific or sensitive as the other autoantibodies. It is found in about 60% of patients with coeliac disease and about 25% of patients with dermatitis herpetiformis.
tTG can also be used to monitor adherence to the diet.
These autoantibodies are often requested together with other tests to help determine the severity of the disease, the extent of the patient’s malnutrition and malabsorption, and organ involvement. Other tests may include:
FBC (full blood count) to look for anaemia
ESR (erythrocyte sedimentation rate) to assess inflammation
CRP (C-reactive protein) to assess inflammation
CMP (comprehensive metabolic panel) to measure electrolytes, protein and calcium levels, and to check the condition of the liver and kidneys
Vitamins D, E and B12 to measure vitamin deficiencies
Faecal fat, to help assess malabsorption
When is it requested?
Coeliac tests are requested when someone has symptoms suggesting coeliac disease, malnutrition and/or malabsorption, such as diarrhoea, abdominal pain, weakness, tiredness, weight loss and joint pain. They may be requested as part of the investigation of anaemia, osteoporosis, infertility or seizures (some types are linked to coeliac disease). In children, coeliac tests may be requested when a child has delayed development or short stature and/or is failing to thrive.
People without symptoms may be tested if they have relatives with coeliac disease, but coeliac tests are not recommended for screening the general population.
Autoantibody levels may also be requested when a patient with coeliac disease has been on a gluten-free diet for some time. This is done to check that antibody levels have fallen and that the diet has been effective in relieving symptoms and allowing the intestinal lining to return to normal (this is sometimes confirmed with a second biopsy). When a patient’s symptoms have not improved, coeliac tests may be requested to check adherence to the diet and to help the doctor and patient look for hidden gluten in the patient’s diet or for other reasons why their symptoms have not improved.
What does the test mean?
In general, if your anti-tTG test is positive, you probably have coeliac disease. If the anti-tTG test is negative, you are more likely not to have coeliac disease. However, your anti-tTG levels may be very low or undetectable if you have avoided wheat, rye and barley for some time, or if you are one of the small percentage of patients with coeliac disease who are also IgA deficient. This can lead to a false negative result and may prompt your doctor to carry out further tests.
If several of the other autoantibodies are present at high concentrations but tTG is negative, you may still have coeliac disease. If only one autoantibody is high, or if one or more are present but only at low concentrations, your symptoms may be due to coeliac disease or to another cause. If the blood test results are positive (or inconclusive), the doctor will usually carry out an intestinal biopsy to confirm or rule out coeliac disease.
If you have been diagnosed with coeliac disease and have removed gluten from your diet, your autoantibody levels should fall. If this does not happen, or your symptoms do not improve, there may be hidden gluten in your diet that has not been eliminated (gluten is often found in unexpected foods, from salad dressings to cough syrups), or you may have one of the rare forms of coeliac disease that do not respond to a change in diet. In many cases, when coeliac tests are used to monitor progress, rising autoantibody levels indicate that the gluten-free diet is not being fully followed.
If you changed your diet and eliminated gluten in the days or weeks before seeing the doctor, coeliac disease may not be detectable. In this case the doctor may use a gluten challenge, reintroducing gluten into the diet for several weeks or months to see whether the symptoms return, and then carry out a biopsy to look for villous atrophy (damage to the intestinal villi).
Is there anything else I should know?
Although coeliac disease is relatively common, with about 1 in 300 people in the US thought to be affected, many people have the disease without knowing it. This is partly because the symptoms vary: they can be mild or even absent, even when intestinal damage is present in the biopsy tissue. Because these symptoms can also be caused by a variety of other diseases, a diagnosis of coeliac disease can be missed or delayed, sometimes for years
1. What is the difference between coeliac disease and an allergy to wheat or other cereals?
2. Can you grow out of or become desensitised to coeliac disease?
3. Do I need to follow a gluten-free diet if I have been diagnosed with coeliac disease but have never had symptoms?
4. Can I include oats in my diet?
5. How do I know what to eat and where can I find help?
1. What is the difference between coeliac disease and an allergy to wheat or other cereals?
Allergies involve hypersensitivity reactions and the production of IgE antibodies specific to cereals such as wheat and rye. These antibodies can cause some symptoms similar to those of coeliac disease, but only for a short time after you have eaten the food you are allergic to. The reaction can be mild or severe but is limited and does not damage the intestinal lining. If you think you may have an allergy to cereals or wheat, ask your doctor, who can test your specific IgE antibodies.
2. Can you recover from or become desensitised to coeliac disease?
No. Coeliac disease does not go away. Once you have been diagnosed, you will need to follow a gluten-free diet for life. If you start eating gluten again, you will damage your intestinal lining again, although it may take some time for the symptoms to return.
3. Do I need to follow a gluten-free diet if I have been diagnosed with coeliac disease but have never had symptoms?
If you have coeliac disease without symptoms, a gluten-free diet is recommended. You will still have damaged villi in your intestine and may have malabsorption problems that cause silent conditions such as osteoporosis. If you have doubts about the accuracy of your diagnosis, you can work with your doctor to check the results.
4. Can I include oats in my diet?
This is somewhat controversial. Some experts feel that people with coeliac disease should avoid oats, while others believe that many patients can tolerate small amounts. They think that the proteins found in oats do not contribute significantly to coeliac disease. This is something to discuss with your doctor and a dietitian.
5. How do I know what to eat and where can I find help?
Your doctor has information about coeliac disease for you. You can also look up the links provided with this article for more information and for organisations that run support groups. Because the disease is very common (once diagnosed), help can be found everywhere