Blood draw
Celiac Disease: IgA/IgG Transglutaminase
IgA and IgG against transglutaminase; for celiac disease screening.
€ 78,00
All tests
Gut · Blood
Transglutaminase (tTG) IgA
Antibodies the body makes in celiac disease; the first blood test when celiac disease is suspected, only reliable if you eat gluten.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
Transglutaminase (tTG) IgA: what is measured?
In celiac disease, the immune system reacts to gluten, a protein found in wheat, barley and rye, among others. In doing so, the body makes antibodies against one of its own proteins in the gut wall: tissue transglutaminase (tTG). The test measures these antibodies of the IgA type, the kind made mainly in the gut. The amount is related to the damage to the gut wall and falls when someone stops eating gluten.
What can it detect?
- Celiac disease (gluten intolerance, an autoimmune disease of the small intestine)
- Checking whether a gluten-free diet is being followed properly, in diagnosed celiac disease
Result
What does the result mean?
Transglutaminase (tTG) IgA too high
A raised tTG IgA makes celiac disease likely; the higher the value, the greater the chance. Symptoms that may go with it are diarrhea or, on the contrary, constipation, abdominal pain, a bloated feeling, weight loss, tiredness, anemia due to iron deficiency and tingling in the hands or feet; some people have no symptoms. A slightly raised value is sometimes a false positive, for example with other autoimmune diseases or shortly after type 1 diabetes develops. The diagnosis is not made on this test alone.
Transglutaminase (tTG) IgA too low
A low or negative value makes celiac disease unlikely, but only if you ate gluten normally in the weeks before and your body makes IgA normally. If you already eat a gluten-free or low-gluten diet, you can get a false negative result. With a congenital lack of IgA (IgA deficiency), the test is also unreliably low; an IgG test is then needed. A negative result only says something about this moment: celiac disease can still develop later.
After an abnormal result
With a raised tTG IgA, the GP refers you to the gastroenterologist, who makes the diagnosis with an additional blood test or an endoscopy with biopsies of the small intestine. Do not stop eating gluten on your own initiative before that testing, because the diagnosis can then no longer be made properly.
Reliability
How reliable is the test?
According to the Dutch Society for Clinical Chemistry (NVKC) and the Dutch medical specialists' guideline (FMS) on celiac disease, tTG IgA is the recommended first blood test when celiac disease is suspected, together with total IgA to rule out an IgA deficiency. In the studies in the guideline, the sensitivity ranged from 71 to 100 percent and the specificity from 65 to 100 percent, depending on the test and the group studied. In adults who eat gluten, the gastroenterologist may make the diagnosis without a gut biopsy if tTG IgA is at least 10 times the upper limit and a separate blood test (endomysial antibodies) is positive; in all other cases a biopsy of the small intestine is needed.
What can affect the result?
- The test is only reliable if you eat gluten; on a gluten-free or low-gluten diet, the antibodies fall and the result can be falsely negative.
- With an IgA deficiency (about 1 in 700 people, more often in celiac disease), the result is falsely low; that is why total IgA or an IgG test is measured as well.
- In children younger than 2 years, the value can be falsely low or negative.
- Measurement methods and cut-off values differ between laboratories; a slightly raised value is less reliable than a strongly raised one.
Who it is for
Who is the test useful for?
Useful for
Useful with symptoms that may fit celiac disease, such as long-lasting abdominal symptoms, diarrhea, unexplained weight loss or an unexplained iron deficiency, and in people with an increased chance: a parent, brother, sister or child with celiac disease, type 1 diabetes or an autoimmune disease of the thyroid. If you already eat gluten-free, this test is of little use. For family members without symptoms, according to the NHG guideline, testing has pros and cons: a positive result means a lifelong gluten-free diet, even without symptoms.
How common is it?
About 1 in 100 people in the Netherlands has celiac disease, more often women than men; many of them do not know it. In people with a parent, brother or sister with celiac disease, this is about 10 in 100. Celiac disease is also more common with type 1 diabetes, autoimmune diseases of the thyroid, Down syndrome and Turner syndrome.
Thuisarts.nl (NHG), the NVKC and the Dutch GP guideline (NHG) on food hypersensitivity and celiac disease
Drawbacks and risks
- If you start eating gluten-free yourself after a positive result, before the diagnosis has been made, the follow-up testing becomes unreliable.
- Celiac disease runs in families; a result can also raise questions for parents, brothers, sisters and children. The test says nothing about a hereditary predisposition (that is a DNA test), only about the disease at this moment.
Get tested
Transglutaminase (tTG) IgA: test panels
Transglutaminase (tTG) IgA is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and results- FMS Richtlijnendatabase: Coeliakie en glutengerelateerde aandoeningen, module Serologische diagnostiek bij volwassenen
- NHG-Standaard Voedselovergevoeligheid en coeliakie
- NVKC Zinnige Diagnostiek: Overwegingen bij screenend bloedonderzoek naar coeliakie
- NVKC, allesovertesten.nl: Anti-TTG
- Thuisarts.nl: Ik heb coeliakie
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