- To help in making a diagnosis of coeliac disease
- Monitoring diagnosed patients to assess the effectiveness and degree of adherence to a gluten-free diet.
- To exclude coeliac disease as a cause or association in some other diseases.
Coeliac Disease Tests
There are different categories of patients who may get tested.
1. Patients who have symptoms suggestive of coeliac disease should be tested. These symptoms may include, for example:
- chronic diarrhoea
- abdominal pain
- weight loss
- poor growth or chronic irritability in an infant or child
2. Patients with known coeliac disease may be tested by their doctor to help assess the effectiveness and observance of a gluten-free diet.
3. Patients with type 1 diabetes mellitus and autoimmune thyroid disease at diagnosis.
4. First degree relatives of people with coeliac disease.
5. Patients with metabolic bone disorder (e.g., osteoporosis), reproductive health problems and unexplained neurological symptoms.
A blood sample taken from a vein in your arm
Follow your doctor's instructions. For diagnosis, ingestion of gluten-containing foods for a time period, such as several weeks, is necessary. The test is accurate only if a gluten-containing diet is eaten during the testing process. If the patient is following a normal diet (containing gluten) it is advisable to eat some gluten in more than 1 meal every day for at least 6 weeks before testing.
For monitoring, no preparation is necessary.
Coeliac antibody tests help in the diagnosis of coeliac disease, and also can help to rule out this diagnosis. These tests detect autoantibodies that the body creates as part of an immune response to dietary proteins (such as gluten) found in wheat, rye, and barley. These autoantibodies are involved in inflammation in the gut and damage to the lining of the gut wall. This damage results in symptoms associated with malnutrition and malabsorption. The symptoms may or may not be related to the gastrointestinal tract, and include:
bone and joint pain
- reproductive problems, delayed puberty
- dermatitis herpetiformis
irritability and delayed growth and development in infants & children
Patients with coeliac disease will typically have some but not all of these symptoms. None of these symptoms are diagnostic of coeliac disease, as they can be found in other (gut) conditions.
A number of autoantibodies not normally present in the blood may be detected in sufferers of this condition:
- Anti-tissue Transglutaminase Antibody (TTG), IgA: Tissue transglutaminase is an enzyme responsible for crosslinking (joining) certain proteins, and is found in the gut as well as in other tissues. It has been identified as the target molecule for the anti-endomysial antibodies. Although 'tissue' is in the name of this autoantibody, it nevertheless involves testing blood and not tissue.
- Anti-Endomysial Antibodies (EMA, IgA): Endomysium is the thin connective tissue layer that covers individual muscle fibres. Anti-endomysial antibodies develop as part of the ongoing damage to the intestinal lining.
- IgG Deamidated gliadin peptide antibodies are autoantibodies that have been used to evaluate suspected coeliac disease when IgA is deficient.
There are 5 types of antibody (IgG, IgA, IgM, IgD and IgE) in the body. Both IgG and IgA types of each autoantibody will often be present in the blood, and may be tested for. Routinely in many laboratories IgA antibodies are used as the first line test for coeliac disease, with other antibody tests (IgG) being performed when IgA is deficient.
In the past, the only way to diagnose coeliac disease was to take a biopsy (small piece of tissue) from the small intestine and to examine it under the microscope. This test is still sometimes used to confirm or exclude a diagnosis of coeliac disease. It may be performed on patients with negative test results but high clinical suspicion. It is also required in diagnosing patients with positive blood tests where the concentration of antibody is not high enough to be diagnostic. The patient should have diet containing gluten until the biopsy is performed. It is carried out in gastrointestinal specialist centres.
HLA DQ2/DQ8 typing is a highly specialised test that may be used in diagnosis of coeliac disease, but only in specialist hospitals/centres. It is indicated for a selected group of patients (e.g., in children who are not having a biopsy)
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
Follow your doctor's instructions. For diagnosis, ingestion of gluten-containing foods for a time period, such as several weeks, is necessary. If the patient is following a normal diet (containing gluten) it is advisable to eat some gluten in more than one meal every day for at least 6 weeks before testing.
For monitoring, no preparation is necessary.
How is it used?
1. For the diagnosis of patients
Coeliac disease tests are used to screen for and help diagnose or exclude coeliac disease. They are usually requested on those patients with symptoms suggesting coeliac disease, but may also be requested to help rule out coeliac disease as a cause for conditions such as anaemia and abdominal pain.
Testing may be performed to screen for coeliac disease in people who do not have symptoms, but who do have close relatives with coeliac disease. About 10% of people who have close relatives with coeliac disease will develop it themselves.
Coeliac disease tests may also be requested in people who have other autoimmune diseases such as type 1 diabetes mellitus, or thyroid disease as patients with autoimmune diseases often have more than one autoimmune disease.
Testing may also be carried out in patients with metabolic bone disorders (e.g.; osteoporosis or pathological fractures), unexplained neurological symptoms and unexplained reproductive health problems (e.g.; subfertility, recurrent miscarriages)
A doctor may use one or more coeliac disease tests, along with other tests to evaluate the status and extent of a patient’s malnutrition and malabsorption.(e.g.; calcium, vitamin D, haemoglobin, vitamin B12 and folate)
Total immunoglobulin A (IgA) and IgA Anti-tissue Transglutaminase Antibody (TTG) are usually the first choice tests performed for diagnosis of coeliac disease. IgA deficiency is significantly more common in people with coeliac disease in general population. That may give a false negative result when tested for IgA TTG, which may lead to a missed diagnosis. That explains the main reason for performing these two tests together If the results of the tests described above are uncertain, then the next test that may be performed is IgA antiendomysial antibody (EMA). This can be a helpful test when the IgA TTG result is weakly positive.
The final tests that may be used are IgG EMA, IgG deamidated gliadin peptide or IgG anti TTG. These may be performed if IgA deficiency is confirmed.
If the results of autoantibody testing are positive, or if clinical suspicion remains high despite of negative findings, the patient should be referred to a gastrointestinal specialist to undergo biopsy of the small intestine (gut) to confirm or exclude the diagnosis of coeliac disease.
Some other tests may be performed to help determine the severity of the disease and the extent of a patient’s malnutrition, malabsorption, and organ involvement. These might include a:
- FBC (full blood count) to look for anaemia
- ESR (erythrocyte sedimentation rate) to evaluate inflammation
- CRP (C-Reactive protein) to evaluate inflammation
- Biochemistry testing to determine sodium, potassium, calcium, and protein concentrations, and to check kidney and liver function
- Iron, folate, vitamin B12, vitamin D, and vitamin E to check for mineral and vitamin deficiencies
2. For monitoring diagnosed patients with coeliac disease
When a patient with coeliac disease has been on a gluten-free diet for a period of time, autoantibody concentrations should decrease. The improvement in symptoms, together with disappearance of the autoantibodies from the blood is a good marker of improvement in the inflammation in the gut wall. However, blood testing alone is not used to determine whether gluten has been excluded from the patient’s diet. It includes measuring weight (and height if a child), reviewing symptoms and looking for other complications. When a patient’s symptoms have not subsided and coeliac disease tests remain positive further actions may be necessary. Intestinal biopsy is an investigation that is helpful in this situation. Some patients are diagnosed as having refractory coeliac disease, which needs specialist advice and further investigations.
When is it requested?
Coeliac disease tests are requested:
- when someone has symptoms suggesting coeliac disease, malnutrition, and/or malabsorption - such as diarrhoea, abdominal pain, bloating, weakness, fatigue, and weight loss
- during the investigation of a wide range of conditions such as anaemia, osteoporosis, unexplained subfertility, and neurological symptoms
- in children, when there is delayed development, short stature and/or a failure to thrive
- if someone has a close relative with coeliac disease
- if someone has an autoimmune disease, such as type 1 diabetes mellitus, or thyroid disease
- to monitor the success of a gluten free diet
Currently coeliac disease testing is not recommended as a screen for the general population.
What does the test result mean?
In general, if your anti-TTG test result is at least moderately or strongly positive, then it is likely that you have coeliac disease. However, a positive anti –TTG test alone is not sufficient for diagnosis. Confirmation is necessary with a second test, either a blood test or an intestinal biopsy.
If the anti-TTG IgA test result is negative, then it is most likely that you do not have coeliac disease. However, your anti-TTG IgA concentrations may be very low or undetectable if you have been avoiding wheat, rye, and barley for a period of time or if you are one of the patients with coeliac disease who are also deficient in IgA. This may lead to a false negative result and may prompt your doctor to request IgA anti-EMA.
If the anti-EMA IgA is positive but the anti-TTG IgA autoantibody is negative, then it is still possible you may have coeliac disease. Hence your doctor may consider additional antibody testing with IgG EMA, IgG DPG or IgG anti-TTG. Usually, intestinal biopsy is the last option to confirm or rule out coeliac disease if these tests are still negative.
If you have been diagnosed with coeliac disease and have removed gluten from your diet, then your autoantibody concentrations should fall. If they do not, and your symptoms do not diminish then there may either be hidden forms of gluten in your diet that have not been eliminated (gluten is often found in unexpected places, from salad dressings to cough syrup) or you may have one of the rare forms of coeliac disease that does not respond to dietary changes. In most cases, when coeliac disease tests are used to monitor progress, rising concentrations of autoantibodies indicate some form of non-compliance with a gluten-free diet.
If you have changed your diet, eliminating gluten days or weeks prior to visiting your doctor, then your coeliac disease autoantibodies may not be detectable. In this case your doctor may do a gluten challenge – have you put gluten back into your diet for several weeks or months to see if the symptoms return, then recheck autoantibodies, and consider whether a biopsy of the intestine is necessary.
Is there anything else I should know?
Although coeliac disease is relatively common (about 1 in 100 people in the UK are thought to be affected) most people who have the disease are not aware of it. This is partly due to the fact that the symptoms are variable and may be mild or absent, even when intestinal damage is present in the gut wall. Since these symptoms may also be due to a variety of other conditions a diagnosis of coeliac disease may be missed or delayed.
What is the difference between coeliac disease and an allergy to wheat and other cereals?
People may develop allergies to any foods, including cereals such as wheat and rye. Genuine food allergies involve immediate reactions and the production of specific IgE antibodies. These IgE antibodies if produced in response to wheat or rye may cause some symptoms similar to those caused by coeliac disease but they will only do so for a short time after eating the triggering food. The reaction may be mild or severe but does not cause chronic damage to the lining of the intestine in the same way that coeliac disease does. Symptoms of food allergy may not be confined to the gut, and can cause rashes, swelling such as of the face, and in the worst cases a severe allergic reaction (anaphylaxis). If you feel that you may have wheat or other grain allergy, talk to your doctor. They can arrange a blood test for these specific IgE antibodies, or arrange referral to an allergy specialist who can perform a more detailed assessment and undertake skin prick testing. It is important to know also that false positive specific IgE antibodies can be found in patients with grass-pollen hay fever.
Can you outgrow or desensitise yourself to coeliac disease?
Do I need to follow a gluten-free diet if I have been diagnosed with coeliac disease but have never had any symptoms?
If you do have a diagnosis of coeliac disease but have no symptoms, it is still recommended that you follow a gluten-free diet. You will still have damaged tissue in your intestines, and you may have malabsorption problems that are causing silent conditions such as osteoporosis. If you have doubts about the accuracy of your diagnosis you may want to work with your doctor to verify the findings.
Can I have Oats in my diet?
This is somewhat controversial. Some experts feel that those with coeliac disease should avoid oats while others believe that most patients can tolerate small amounts of it. They feel that the proteins found in the oats are not contributing significantly to the coeliac disease. This is something you should discuss with your doctor and a dietician.
On This Site
Tests: FBC, ESR, CRP, Calcium, Total Protein, Albumin, Vitamin D, Vitamin B12, Vitamin E, Iron, Folate, Total IgA, Anti-Endomysial Antibodies (EMA), Anti-tissue
Conditions: Coeliac disease, Autoimmune disorders, Malnutrition, Malabsorption, Iron Deficiency Anaemia, Osteoporosis, Lactose intolerance, Inflammatory Bowel Disease