Celiac Disease Blood Tests and Biopsy--Diagnosing Celiac Disease
Celiac disease blood tests are usually the first of two main
steps in diagnosing celiac disease.
Traditionally there was a panel of tests used known as the
celiac panel. This panel included:
-AGA IgA (anti-gliadin antibody)
-AGA IgG (anti-gliadin antibody)
-tTG IgA (anti-tissue transglutaminase)
-Total IgA and sometimes -tTg EMA (anti-endomysium)
-DGP IgA, IgG (Deaminated Gliadin Peptide)(newer)
Currently most doctors seem to rely on a single test, the tTG
IGA or anti-tissue transglutaminase. The tTG test is highly
specific for Celiac Disease and only rarely gives a false
It can not, however, rule out celiac as it will only pick up
the antibody once it is in the bloodstream. You can still be
susceptible to getting it, or have a mild enough case that
the tTG levels are below the threshold of the test. The test
will also be negative in a person with an IGA deficiency.
Update: The DGP IgG test can pick up cases where the tTG IgA is
negative. It also is more reliable in the case of an IgA
deficiency. Best results are with DGP-IgG for those with IgA
deficiency. A DGP IgG used in conjunction with IgA tTg will
find more positives even when there is no IgA deficiency.
This study shows the number of positive tTg test results on people
who showed endoscopic evidence of celiac disease in various
stages. It picked up almost every severe case, but a much
smaller percentage (about 31%) of mild cases.
Note: The study opens in a new window. If you have trouble
opening it, you may need to hold down your control key while
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Journal of Clinical Gastroenterology
The following study shows the results of tests on biopsy
positive cases in the use of the IgA tTG and the IgG DGP:
The Intestinal Biopsy
If the person being tested does get a positive tTG test, then
the next step after the celiac disease blood tests is to have
an endoscopy. The doctor will insert an endoscope down through
the throat and the stomach to the small intestine. There,
generally from 4 to 8 tissue samples are taken for biopsy.
This tissue that was biopsied is then viewed under a
microscope and classified according to the Marsh
system. If the damage is patchy then it may be hit and miss
as far as the biopsy finding it.
The Marsh system goes from 0 to 4, with 0 being normal and 4
being complete villous atrophy or a flat intestinal wall.
If you have a 1 or a 2, you may have some changes in the
epithelium where enterocytes have infiltrated or penetrated
This leads to "leaky gut", where the gliadin can enter the
bloodstream. Also other food proteins can pass through and
you may be reacting to many of these once they are able to
At 3 you have partial or total villous atrophy plus the more
permeable gut tissue, and at 4 you have no villi left, and the
wall of the small intestine is flat and has a scalloped
appearance in folds.
The blood test and the intestinal biopsy by endoscopy are the
"gold standard" for diagnosing celiac disease. The third step
is for the doctor to monitor the results on a gluten free
diet. If there is great improvement within six months, then
that is taken as confirmation that the person has celiac
If you had a negative tTG test, and still think you might have
celiac disease or at least a sensitivity to gluten, see the
home test for gluten testing under the Gluten Sensitivity
from Celiac Disease Blood Tests to What is Celiac Disease
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