To help diagnose celiac disease and to evaluate the effectiveness of a gluten-free diet
Celiac Disease Antibody Tests
When you have symptoms suggesting celiac disease, such as chronic diarrhea, bloating, abdominal pain, anemia, and weight loss; when an infant is chronically irritable or fails to grow at a normal rate; when a close family member has celiac disease; when you are being treated for celiac disease
A blood sample drawn from a vein in your arm
Follow your healthcare practitioner's instructions. For diagnosis, you should continue to eat foods that contain gluten for a time period, such as several weeks, prior to testing. For monitoring celiac disease when you have already been diagnosed, no preparation is necessary.
Celiac disease is an autoimmune disorder characterized by an inappropriate immune response to gluten, a protein found in wheat, and related dietary proteins in rye and barley. Celiac disease antibody tests help diagnose and monitor the disease and a few other gluten-sensitive conditions. These tests detect autoantibodies in the blood that the body produces as part of the immune response.
This immune response leads to inflammation of the small intestine and to damage and destruction of the villi that line the intestinal wall. The villi are projections, small tissue folds that increase the surface area of the intestine and allow nutrients, vitamins, minerals, fluids, and electrolytes to be absorbed into the body. When a susceptible person is exposed to gluten, the person's body produces autoantibodies that act against constituents of the intestinal villi. When villi are damaged or destroyed, the body is much less capable of absorbing food and begins to develop signs and symptoms associated with malnutrition and malabsorption.
A tissue biopsy of the small intestine is still considered the gold standard to use to confirm a diagnosis of celiac disease, but the availability of less invasive blood tests to screen for celiac disease has reduced the number of biopsies needed.
See "How is the test used?" below for details on the tests.
- How is the test used?
Celiac disease antibody tests are primarily used to help diagnose and monitor celiac disease in people with signs and symptoms, including anemia and abdominal pain.
Sometimes celiac testing may be used to screen for asymptomatic celiac disease in those who have close relatives with the disease since about 4-12% of them have or will develop celiac disease. Testing may also be ordered in those who have other autoimmune diseases.
Celiac disease blood tests measure the amount of particular antibodies in the blood. The most common tests include:
- Tissue transglutaminase antibody (tTG), IgA class — the primary test ordered to screen for celiac disease. It is the most sensitive and specific blood test for celiac disease and is the single test preferred by the American College of Gastroenterology and the American Gastroenterology Association for the detection of celiac disease in those over the age of 2 years. If the test is positive, it can also be used to monitor the condition and to help evaluate the effectiveness of treatment. (Although "tissue" is in the name of this test, it is measured in the blood.)
- Immunoglobulin A (IgA) — this test is usually ordered along with the tTG IgA test (below) to detect IgA deficiency, which occurs in about 2-3% of people with celiac disease. If you have an IgA deficiency then the test for tTG IgA may be negative even if you have celiac disease (false-negative test results). If the IgA test shows you have an IgA deficiency, then a test to detect the IgG class of autoantibodies may be ordered (see below).
- tTG, IgG may be used as an alternative test in people who have a deficiency of IgA.
Deamidated gliadin peptide (DGP) antibodies (anti-DGP), IgA or IgG — may be used in some people with suspected celiac disease who are negative for anti-tTG, especially children younger than 2 years old. DGP IgG testing along with anti-tTG IgG is recommended by the American College of Gastroenterology for people who have low IgA or IgA deficiency. If the anti-DGP test is positive, it may be used to monitor celiac disease.
Tests that are used less often include:
- Anti-endomysial antibodies (EMA) -— antibodies developed in reaction to the ongoing damage to the intestinal lining; it has been found that tTg is the substance detected in this test. Almost 100% of people with active celiac disease and 70% of those with dermatitis herpetiformis (another gluten-sensitive condition that causes an itchy, burning, blistering rash on the skin) will have the IgA class of anti-EMA antibodies. The test is more difficult to do and interpret properly than anti-tTg so it is used less often.
Anti-reticulin antibody (ARA) test — not as specific or sensitive as the other autoantibodies; it is found in about 60% of people with celiac disease and about 25% of those with dermatitis herpetiformis; it is rarely ordered.
To confirm a diagnosis of celiac disease, a biopsy of the small intestine is examined to detect damage to the intestinal villi. However, given the invasive nature and cost of a biopsy, antibody tests are often used to identify those individuals with high probability of having celiac disease. (For general information on biopsies, see the article on Anatomic Pathology.)
- When is it ordered?
Celiac disease tests are ordered when someone has signs and symptoms suggesting celiac disease, malnutrition, and/or malabsorption. The symptoms are often nonspecific and variable, making the disease difficult to spot. The symptoms may, for a time, be mild and go unnoticed and then progressively worsen or occur sporadically. The condition can affect different parts of the body.
Digestive signs and symptoms may include:
- Abdominal pain and distension
- Bloody stool
- Chronic diarrhea or constipation
- Greasy, foul-smelling stools
Other signs and symptoms may include:
- Iron-deficiency anemia that does not respond to iron supplements
- Easy bruising and/or bleeding
- Bone and joint pain
- Defects in dental enamel
- Fatigue, weakness
- Mouth ulcers
- Weight loss
In adults, infertility, osteoporosis
In children, celiac disease tests may be ordered when a child exhibits:
- Digestive tract symptoms
- Delayed development
- Short stature
Failure to thrive
Many people with celiac disease have dermatitis herpetiformis, a disease that causes itchy blisters on the skin. There is also an increased risk for developing intestinal lymphoma, a form of cancer.
One or more antibody tests may be ordered when someone with celiac disease has been on a gluten-free diet for a period of time. This is done to verify that antibody levels have decreased and to verify that the diet has been effective in reversing the intestinal lining damage (this is sometimes still confirmed with a second biopsy).
Asymptomatic people may be tested if they have a close relative such as a parent or sibling with celiac disease, but celiac disease testing is not recommended at this time as a screen for the general population.
- What does the test result mean?
Some celiac disease tests and possible results tTG, IgA Total IgA tTG, IgG DGP, IgA DGP, IgG Diagnosis Positive Normal Not performed Not performed Not performed Presumptive celiac disease Negative Normal Negative Negative Negative Symptoms not likely due to celiac disease Negative Low Positive Negative Positive Possible celiac disease (false negative anti-tTG, IgA and anti-DGP, IgA are due to total IgA deficiency) Negative Normal Negative Positive Positive (or not performed) Possible celiac disease (may be seen in children less than 3 years old)
All positive and indeterminate celiac disease tests are typically followed by an intestinal biopsy. A biopsy is used to make a definitive diagnosis of celiac disease.
If you have been diagnosed with celiac disease and you eliminate gluten from your diet, then the autoantibody levels should fall. If they do not fall and the symptoms do not diminish, then there may either be hidden forms of gluten in the diet that have not been eliminated (gluten is often found in unexpected places, from salad dressings to cough syrup to the adhesive used on envelopes) or you may have one of the rare forms of celiac disease that does not respond to dietary changes.
If you have not consumed any gluten for several weeks to months prior to testing, then celiac disease tests may be negative. If your healthcare practitioner still suspects celiac disease, the practitioner may do a gluten challenge – have you introduce gluten back into your diet for several weeks or months to see if your symptoms return. At that time, celiac disease tests may be repeated or a biopsy may be done to check for damage to the villi in the intestine.
- Is there anything else I should know?
Although celiac disease is relatively common (about 1 in 100 to 150 people in the U.S. 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 -- they may be mild or absent, even when intestinal damage is present on biopsied tissue. Since these symptoms may also be due to a variety of other conditions, a diagnosis of celiac disease may be missed or delayed, sometimes for years.
- Besides antibody tests, what other tests may be ordered?
Additional tests may be ordered to help determine the severity of the disease and the extent of the complications a person may experience, such as malnutrition, malabsorption, and the involvement of other organs. Examples include:
- Anti-F-actin — may sometimes be ordered if a person has been diagnosed with celiac disease and a healthcare practitioner wants to evaluate the severity of intestinal damage; a positive result may indicate increased intestinal damage.
- CBC (complete blood count) to look for anemia
- CRP (C-Reactive protein) to evaluate inflammation
- CMP (comprehensive metabolic panel) to determine electrolyte, protein, and calcium levels, and to verify the status of the kidney and liver
- Vitamin D and B12 and folate to detect vitamin deficiencies
- Iron, iron binding capacity or transferrin, and ferritin to detect iron deficiency
Stool fat, to help evaluate malabsorption
Since those with celiac disease may also experience conditions such as lactose intolerance, celiac tests may be done in conjunction with other intolerance and allergy testing.
- What is gluten and what contains gluten?
Gluten is a protein that is naturally present in cereal grains, especially wheat, and is responsible for the elastic texture of dough. It can be found in many foods, acting as a 'glue' that helps foods maintain their shape. Examples of these foods include:
- Breads and other baked goods
In addition to wheat, gluten may be found in many other grains, such as:
- What is the difference between celiac disease and an allergy to wheat and other grains?
Allergies involve hypersensitivity reactions and the production of specific immunoglobulin E (IgE) antibodies directed against grains such as wheat and rye. These antibodies may cause some symptoms similar to those caused by celiac disease, but they will only do so for a short time after you eat the food to which you are allergic. The reaction may be mild or severe, but it is limited and does not cause damage to the lining of your intestine the way that celiac disease does. If you feel that you may have a wheat or other grain allergy, talk to your healthcare practitioner about getting tested for these allergen-specific IgE antibodies.
- Can you outgrow or desensitize yourself to celiac disease?
No. Celiac disease does not go away. Once you have been diagnosed with celiac disease, you will need to follow a gluten-free diet for life. If you start eating gluten again, you will damage the lining of your intestines; it just may take a while for the symptoms to come back.
- Do I need to follow a gluten-free diet if I have been diagnosed with celiac disease but have never had any symptoms?
If you have asymptomatic celiac disease, it is recommended that you follow a gluten-free diet. You will still have damaged villi 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 health practitioner to verify the findings.
- Can I have oats in my diet?
This is somewhat controversial. Some experts feel that oats should be avoided by those with celiac disease while others believe that most people can tolerate small amounts. They feel that the proteins found in oats are not contributing significantly to celiac disease. This is something you should discuss with your healthcare practitioner and a nutritionist.
- How do I know what to eat and where can I get help?
Your healthcare practitioner will have information for you on celiac disease. You can also visit the links listed at the end of this article under Related Content for several organizations that have resources, including support groups.
- Are there other ways to test for celiac disease?
Genetic tests that look for the markers that are strongly associated with celiac disease have recently become available. These tests look for the Human Leukocyte Antigen (HLA) markers DQ2 and DQ8. A positive result does not diagnose celiac disease since about 30% of the general population also carry these markers but do not have the disease. However, almost all people with celiac disease are positive for DQ2 or DQ8, so a negative result can essentially rule out celiac disease in those individuals for whom results of other tests, including biopsy, are unclear. These tests are most useful for family members of individuals with the disease that fall into a high-risk category and for those with other diagnostic test results that are inconclusive.