This article focuses on the two main antibody blood tests for celiac disease. It will tell you what each test looks for and what the results mean.
The two blood tests recommended when testing for celiac disease are the AGA-IgA test for gliadin (wheat proteins) as well as the tTG-IgA test for tissue transglutaminase.
Recent research indicates the blood tests most doctors are using, tTG & EMA, are not as reliable as first thought. Young children, elderly, smokers, the very ill and the not very ill can be missed. EMA, or endomysial antibodies has fallen out of favor so they will not be discussed.
Preparation for Testing
Make sure when being tested that you are on a gluten-containing diet, because the antibodies the tests look for would disappear if you are were gluten-free. Once you go gluten-free, future testing is unreliable.
AGA – The Test for Gluten Sensitivity
The AGA-IgA has fallen out of favor for CELIAC DISEASE, but it tests whether an immune reaction against GLUTEN (gliadin) is present in the system – it detects a GLUTEN SENSITIVITY reaction. You can have gluten sensitivity without developing the lesion that is characteristic of celiac disease. That is, you can have gluten sensitivity without celiac disease.
tTG – The Test for Celiac Disease
tTG tests for tissue transglutaminase antibodies, or antibodies against your own tissues. The tTG blood test does NOT tell you if you have celiac disease per se. It tells you the likelihood that villous atrophy will be discovered if an endoscopy with biopsy is performed. The higher the number, the more likely you have enough damage that one of the samples would show villous atrophy.
One thing to consider is that you have over 20 feet of small intestine. Biopsy samples are tiny and only about 5 are taken. How much damage is required before a positive biopsy sample is found?
Also, you can also have the beginning stages of celiac disease and the test results will be "negative" now, but if you were tested at a later date they could rise, making you positive. That is, the levels of antibodies now may not indicate probable intestinal damage enough to be found on endoscopy with biopsy. But they can rise over time – one month, six months, a year.
In one study we reviewed while creating the medical manual, Recognizing Celiac Disease, of the children who tested positive in the study, 40% had tested negative 5 years previously.
No test is 100% accurate. Determining celiac disease is still a judgment call. Even if the tests come back negative, try a strict 100% gluten free diet to see if symptoms improve. If they do, ask your doctor to take multiple vitamin and mineral levels to determine whether deficiencies exist.
Page 30 in Recognizing Celiac Disease lists the vitamins and minerals the NIH recommends checking: vitamins A, D, E, K, B12, folic acid and minerals calcium, iron, phosphorous.
The symptom charts in the book list which deficiencies cause which symptoms so you can determine which nutrient levels to test and give your doctor reasons to test for them. (Doctors will not take nutrient levels unless there is a reason to take them.) Correct the nutrient deficiencies and you will correct the symptoms in many cases.
A diagnosis is just a diagnosis. Good health is the most important thing.
For more information on the tests click here.
For more information on Recognizing Celiac Disease click here.
Author Information: John Libonati, Philadelphia, PA
President-elect, Celiac Sprue Association (CSA).
Editor & Publisher, Recognizing Celiac Disease.
John can be reached at firstname.lastname@example.org.