A celiac disease test detects antibodies in the blood serum that are typical of gluten intolerance. In some cases, however, there is a celiac disease, although the test does not strike. Then further examinations are necessary to be able to ensure the diagnosis of celiac disease. Read here how the celiac disease test works and what you should be aware of.
Celiac Disease Test: Antibody
If there is a suspicion of gluten intolerance, a gluten allergy test should be carried out before a change in diet. The doctor takes a blood sample and examines them for certain immunoglobulins. These are antibodies directed against transglutaminase (anti-TG) and endomysium (EmA).
Transglutaminase is a protein (enzyme) in the intestinal mucosa, which processes the glutamine contained in the gluten. In celiac disease, the body produces antibodies to the enzyme. They circulate in the blood and attack the transglutaminase, whereupon the intestinal mucosa becomes inflamed.
In addition, the immune system in people with celiac disease and antibodies to the so-called endomysium. The endomysium is a connective tissue layer in the intestinal wall. If it is attacked, the villi of the intestinal wall degrade. The concentration of the endomysium antibodies therefore allows a conclusion on how strongly the intestinal villi are regressed.
The celiac disease test should also determine the total amount of class A antibodies (immunoglobulin A / IgA).
Physicians divide immunoglobulins into several classes: G, A, M, D and E. The transglutaminase and endomysium antibodies active in celiac disease belong to group A.
A gluten intolerance is often accompanied by an IgA deficiency. This is problematic for the diagnosis: If the total amount of antibodies is too low, antibodies against the transglutaminase or the endomysium can not or only with difficulty be detected in a blood test. Doctors call this a false-negative test result. By this it is meant that the all-clear is wrongly given, even though the typical celiaki antibodies are actually present in the blood.
The easy-to-perform celiac disease test detects over 74 percent of people with gluten intolerance. If this celiac test is negative at a normal IgA concentration, gluten intolerance is very unlikely.
Celiac disease test for IgA deficiency
In another celiac disease test, antibodies against the gluten component gliadin are detected. However, this test only makes sense in the case of an IgA deficiency. It is not carried out as standard in the context of initial celiac disease diagnostics. The accuracy of this test is always up for discussion. Instead, in case of an existing IgA deficiency, transglutaminase antibodies of the group IgG can also be determined.
Celiac self-test
Meanwhile, various manufacturers offer celiac disease tests in different price ranges. They can also be used to detect the antibodies that are typical of celiac disease, transglutaminase and endomysium antibodies in the blood.
How to perform the celiac self-test?
A celiac self-test (also called “gluten self-test”) is similar to a pregnancy test. However, one needs a small drop of blood instead of urine for the self-test. The test kit is available over the counter in pharmacies and on the Internet. It contains a lancet for obtaining a blood drop, a small capillary tube, a test solution in a reaction tube, a pipette and a test cassette.
For the test, the end of the tester sticks with the lancet in the fingertip, so that a small drop of blood protrudes. He takes this up with a small capillary tube. This is placed in a liquid-filled reaction vessel and shaken a little. The tester then aspirates the blood-fluid mixture with a pipette and places a drop on a designated field within the test cassette. After a few minutes, the result can be read on the basis of a color change.
Is the celiac self-test useful?
However, experts of the German Society for Gastroenterology, Digestive and Metabolic Diseases (DGVS) advise against a celiac self-test. The tests are very inaccurate. A gluten self-test can therefore serve as a maximum orientation at most. But he certainly can not replace a detailed medical diagnosis, including the professional blood test and a possible tissue sampling from the small intestine. Similar rapid tests that examine stool or saliva are also not reliable enough, say the experts.
Some manufacturers of the test kits advertise with an alleged almost 100 percent certainty of the test result. However, considering that erroneous results are not ruled out even in a professional, elaborate blood test at the doctor, this claim can hardly stand a serious test. For example, a rapid celiac disease test is susceptible to a faulty test result if there is an immunoglobulin A deficiency in the patient.
After a positive result, the patient must anyway to the doctor, who will carry out the complete diagnosis again. A negative result of the celiac self-test, however, offers only a dubious security. For those insured by the statutory health insurance, many health insurances pay the costs of diagnostics to the doctor, while a celiac disease self-test must be paid out of one’s own pocket.
Celiac Disease: Breath Air Test (H2 breath test)
In severe celiac disease, a large part of the intestinal villi has receded. This reduces the surface of the intestine and the nutrients can only partially pass into the blood (resorption disorder). In some of these indigestion, this also applies to the sugar molecule xylose. It therefore enters the colon with the remaining food pulp, where it is split by bacteria. This produces hydrogen (H2), which is transported to the lungs and then exhaled.
In a xylose test, the doctor measures the H2Concentration in the breathing air of a fasting patient before and after administration of a xylose-drinking solution. An increased concentration of hydrogen indicates a resorption disorder, the cause of which may be celiac disease. But there are other reasons for a resorption disorder, it is not a specific celiac disease test.
Celiac Disease Test: Children
Although some guidelines for children under the age of two recommend a different antibody diagnosis, the German Society for Gastroenterology, Digestive and Metabolic Diseases (DGVS) recommends the same antibody tests as in adults in its guideline from 2014 for suspected childhood celiac disease.
If antibodies can not be measured in the children’s celiac disease test (including screening tests of high-risk groups), their antibody levels (as opposed to adults) should be rechecked at the following intervals: every six months for the first two years, then after five and after ten years.
In some cases, children with suspected celiac disease may not need a tissue sample from the small intestine. This is the case when the children suffer from symptoms of celiac disease, show typical signs of malnutrition and, moreover, the following four criteria are met:
- In the celiac disease test, the transglutaminase antibodies reach a value ten times higher than the limit.
- Endomysium antibodies can be detected.
- There is a genetic predisposition to celiac disease (HLA-DQ2 and / or -DQ8)
- The symptoms subsided under gluten-free diet.