What this test measures
DGP IgG measures IgG-class antibodies against deamidated gliadin peptide — a modified wheat protein created by the gut transglutaminase enzyme in the small intestine. In celiac disease the immune system mounts both IgA and IgG responses, and the IgG component is particularly useful when the IgA response cannot be assessed.
About 2–3% of patients with celiac disease are IgA-deficient (a common primary immunodeficiency in India and Europe), and they will have a false-negative IgA-based antibody test. DGP IgG and tTG IgG are the antibody tests of choice for them.
Why it matters
DGP IgG is essential in three groups: (1) patients with selective IgA deficiency, (2) children under 2 years of age (the IgG response often appears earlier than IgA at this age), and (3) any patient where the IgA test is equivocal but clinical suspicion of celiac disease remains high. The Indian Society of Gastroenterology recommends testing total IgA alongside tTG IgA in every suspected celiac workup, switching to IgG-based tests when IgA is deficient.
Untreated celiac disease causes growth failure in children, iron-deficiency anemia not responding to iron, osteoporosis, infertility, recurrent miscarriage, and a small lifetime increase in lymphoma risk. Identifying patients early — including those who would be missed by IgA-only testing — is the goal.
How to prepare
Critical: do NOT start a gluten-free diet before the test. Antibodies fall and biopsy heals on gluten avoidance, leading to false-negative results. Continue normal wheat-containing food (at least one daily serving — 1 slice of bread, 2 chapatis, or equivalent) for at least 6 weeks before testing. No fasting needed. Inform the lab if you have a known IgA deficiency or any other immunodeficiency.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| DGP IgG (U/mL (or AU/mL))[1][2][3] | Negative (assay-specific cut-off, typically < 20 U/mL) | Negative: low likelihood of celiac disease in IgA-deficient patients or young children. In an IgA-replete adult, the IgA-based tests are usually more informative — interpret in context. | Positive: suggests celiac disease. Confirm with duodenal biopsy showing villous atrophy. In IgA-deficient patients a positive DGP IgG or tTG IgG is sufficient evidence to proceed to biopsy without needing the IgA tests. |
Which celiac antibody test fits which patient?
| Patient | Best first-line antibody |
|---|---|
| Adult, IgA-replete | tTG IgA + total IgA |
| Adult, IgA-deficient | tTG IgG + DGP IgG |
| Child > 2 years, IgA-replete | tTG IgA + total IgA |
| Child < 2 years | tTG IgA + DGP IgG (IgA response may be late) |
| Equivocal tTG IgA result | Add DGP IgA + DGP IgG |
Frequently asked questions
When is DGP IgG specifically ordered?
In IgA-deficient patients (where tTG IgA gives false negatives), in children under 2, and as a confirmatory test when tTG IgA is equivocal.
Why does IgA deficiency matter for celiac testing?
About 2–3% of celiac patients have selective IgA deficiency — they cannot make IgA antibodies. A standard tTG IgA test will be negative even with severe disease. Switching to IgG-based tests (DGP IgG, tTG IgG) catches these patients.
Do I still need a biopsy?
For adults, yes — duodenal biopsy showing villous atrophy is the gold-standard confirmation. For children, modern ESPGHAN guidelines allow biopsy-free diagnosis under specific conditions (tTG IgA > 10× upper limit plus a confirmatory antibody).
How long should I keep eating gluten before the test?
At least 6 weeks of one daily wheat-containing serving (a slice of bread, two chapatis, or equivalent). Stopping gluten before testing causes false-negative results that delay or miss diagnosis.
How accurate is DGP IgG?
In IgA-deficient patients and young children, DGP IgG sensitivity is 70–90% and specificity > 90%. In the general IgA-replete population, IgA-based tests are slightly more accurate, so they remain first-line.
What is the difference between DGP and the old anti-gliadin antibody (AGA)?
The old AGA test tested antibodies against unmodified gliadin and had poor specificity (many false positives). DGP tests target deamidated gliadin — the chemically modified form the immune system actually attacks — and have much better diagnostic accuracy.
Related Immunology tests
Tests commonly ordered alongside ANTI DEAMIDATED GLIADIN PEPTIDE - IGG, or that help interpret an unexpected result.
Sources & references
- NCBI StatPearls — Celiac Disease · accessed 2026-05-30T00:00:00.000Z
- ACG Clinical Guideline — Celiac Disease · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — Deamidated Gliadin Peptide IgG · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Celiac Disease Tests · accessed 2026-05-30T00:00:00.000Z
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