InstalabDeamidated Gliadin Peptide Antibody
Should you take a Deamidated Gliadin Peptide Antibody test?
This test is most useful if any of these apply to you.
About Deamidated Gliadin Peptide Antibody
If you've had bloating, loose stools, or unexplained iron deficiency, celiac disease belongs on the list of possible causes. This stool test looks for antibodies against altered gluten fragments. Its ability to identify celiac disease or explain your symptoms hasn't been established.
Blood tests for these antibodies have an established role in selected situations. The stool measurement remains exploratory. Evidence about blood antibodies doesn't establish what a stool result means, and published research hasn't shown that adding this stool test improves diagnosis or follow-up.
What the Test Detects
Gliadin is a protein in wheat gluten. Some fragments resist digestion and can be chemically changed by tissue transglutaminase. This change is called deamidation. The resulting fragments are deamidated gliadin peptides, or DGP.
In celiac disease, the immune system responds to gluten and makes antibodies against some of these altered fragments. Antibody-producing cells in the intestinal lining can contribute to this response. IgA and IgG are different classes of antibodies, and IgA can be released into the gut contents.
The catalog identifies this test as a stool DGP antibody immunoassay, but it doesn't specify whether it detects IgA, IgG, or both. That distinction matters: the small stool study discussed below found a difference between people with and without celiac disease for IgA, but not for IgG. Its findings cannot be assumed to describe this particular assay.
An immunoassay detects binding between antibodies and prepared target fragments. This test reports an index based on the assay's calibration. The index isn't an absolute antibody concentration, and results from different assays aren't necessarily comparable, even when both reports use the word "index."
| Measurement | What it detects | What the evidence supports |
|---|---|---|
| Stool DGP antibodies | Antibodies against altered gliadin fragments in stool | An exploratory measurement with unproven diagnostic and monitoring value |
| Blood DGP antibodies | IgA or IgG antibodies against altered gliadin fragments circulating in blood | An established aid in selected celiac evaluations, especially IgG testing when total IgA is deficient |
| Stool anti-gliadin antibodies | Antibodies against gliadin targets that may differ from deamidated peptides | A separate measurement whose evidence cannot automatically be applied to stool DGP antibodies |
| Stool gluten peptides | Fragments of gluten that was eaten | Evidence of recent gluten exposure, with detection depending on the amount eaten and sample timing |
Celiac Disease
Celiac disease is an autoimmune condition in which gluten triggers injury to the small intestine. The damage can reduce nutrient absorption and contribute to diarrhea, iron deficiency, slowed growth in children, and weakened bones. Some uncommon cancers are also more frequent in people with celiac disease.
Most people with celiac disease carry HLA-DQ2 or HLA-DQ8. These inherited immune-system features help present gluten fragments to immune cells, but most people who carry them never develop the disease. A stool antibody result hasn't been shown to predict your future risk of celiac disease or its complications.
What the Stool Research Shows
One small study compared processed stool samples from 25 people with untreated celiac disease and 12 healthy volunteers. Stool DGP IgA levels were higher in the celiac group and correlated with blood DGP IgA. The research assay detected stool DGP IgA in some, but not all, of the celiac group.
That finding supports further investigation, but it doesn't establish how accurately this catalog test works in people with unexplained symptoms. The study used a particular research assay and a small, selected comparison group. Its result cannot establish a reliable false-positive rate or justify using a negative stool result to exclude celiac disease.
A 2024 review identified this DGP study among several small studies of different stool antibodies. Findings across the broader stool-antibody literature were inconsistent. The review did not establish a stool antibody test that reliably measures small-intestinal damage.
What Blood Studies Can Establish
Blood DGP and stool DGP are related measurements with different evidence. In a 2010 meta-analysis, blood DGP IgA detected about 88 of every 100 celiac cases and correctly tested negative in about 94 of every 100 people without the disease. Blood tissue transglutaminase IgA performed better in that comparison. These figures describe the blood assays and study populations included in the analysis.
Current diagnostic guidance uses blood tissue transglutaminase IgA together with total IgA as the usual starting point. IgG-based blood tests have a role when IgA is deficient. European pediatric guidance recommends the same tissue transglutaminase IgA starting point in children of any age who make enough IgA, including those under two, and American guidance also favors tissue transglutaminase IgA as the preferred initial test. Being under two does not establish a need for stool DGP testing.
Blood results also need context. In a study of 40 children with positive blood DGP IgG but negative tissue transglutaminase antibodies, only one had biopsy-confirmed celiac disease, and that child had IgA deficiency. This finding cannot be used to calculate the chance of celiac disease after an isolated positive stool result.
When Results Can Be Misleading
- An unspecified antibody class: IgA deficiency can make an IgA-based antibody result falsely reassuring. The catalog doesn't identify this assay's antibody class, so its behavior in IgA deficiency cannot be assumed.
- Gluten restriction: blood celiac antibodies generally decline after gluten is removed, although they can remain detectable for months or longer. The response and timing of this stool index haven't been established.
- Sample processing and storage: proteins can break down during intestinal passage and after collection. Extraction, transport, and storage need validation for a stool assay; the size of these effects for this test isn't established by the available studies.
- Assay differences: target fragments, antibody classes, extraction procedures, and calibration can differ between immunoassays. Blood assay results and research stool results cannot be converted into this test's index.
- Treating the index as a damage score: a larger stool index hasn't been validated as evidence of more severe intestinal injury, and a smaller result hasn't been validated as evidence of healing.
What Serial Results Can Establish
The evidence doesn't establish how changes in this stool index relate to gluten exposure, symptoms, or healing. Using the same laboratory may avoid differences between assays, but it doesn't make an unvalidated trend clinically meaningful.
Studies of blood DGP have found associations with persistent intestinal damage in treated celiac disease. Even blood antibodies can miss ongoing injury or intermittent gluten exposure. Those limitations give no basis for assuming that stool antibodies provide a more reliable measure.