Deamidated Gliadin Peptide (DGP) IgA/IgG Test

Introduction to the Deamidated Gliadin Peptide (DGP) IgA/IgG Test

When patients walk into my clinic with a puzzling constellation of symptoms—unexplained bloating, chronic fatigue, recurring mouth ulcers, or even a mysterious rash—celiac disease often sits high on my differential list. For years, the tissue transglutaminase (tTG) antibody test has been the go-to screening tool, but it is not perfect. That is where the Deamidated Gliadin Peptide (DGP) IgA/IgG antibody panel comes in. This test detects the immune system’s response to modified gluten peptides and is especially helpful in certain clinical scenarios.

What Is Deamidated Gliadin Peptide (DGP) and Why Is It Measured?

DGP stands for deamidated gliadin peptide. Gliadin is a component of gluten found in wheat, barley, and rye. When the enzyme tissue transglutaminase modifies gliadin, it becomes deamidated, and that altered peptide can trigger an abnormal immune reaction in people with celiac disease. The DGP test measures the levels of IgA and IgG antibodies your body produces against this modified peptide. A positive result suggests that your immune system is reacting to gluten and raises the likelihood of celiac disease.

Who Should Get the DGP Test?

• Individuals with symptoms of celiac disease (diarrhoea, weight loss, bloating, iron-deficiency anaemia) but negative tTG results.
• Patients with selective IgA deficiency—the DGP IgG component is particularly useful here because tTG IgA may be falsely low.
• Younger children, especially those under 2 years old, where the DGP test may have higher sensitivity than tTG.
• Follow-up monitoring after starting a gluten-free diet (though tTG is more commonly used).

How the DGP IgA/IgG Test Is Performed

The test is a simple blood draw. No fasting is required, but it is critical that you are eating a gluten-containing diet for the test to be accurate. In my practice, I advise patients to consume at least one serving of gluten (for example, two slices of bread) daily for at least six weeks before testing. If you have already started a gluten-free diet, the antibodies may decline, and you could get a false-negative result.

Reference Ranges for DGP IgA/IgG

Different laboratories may use slightly different units and cut-offs. The table below shows typical values used in many reference labs. Always interpret results alongside the lab’s specific reference range.

Note: Some labs report results as negative, weakly positive, or strong positive. Always discuss borderline values with your healthcare provider.

Interpreting Your DGP IgA/IgG Results

What Does a Positive DGP IgA/IgG Test Mean?

A positive DGP IgA or IgG result strongly suggests celiac disease, but it is not a diagnosis on its own. I have seen patients with positive DGP antibodies who later had confirmatory small bowel biopsies showing villous atrophy. However, a positive result can occasionally occur in other autoimmune conditions, such as type 1 diabetes or autoimmune thyroid disease, even without full-blown celiac disease. That is why the DGP test is usually combined with tTG IgA and total IgA levels for a complete picture.

DGP Test vs. tTG IgA Test: Which Is Better?

The tTG IgA test is still the first-line screening recommended by most guidelines, including those from the American College of Gastroenterology. DGP antibodies have a slightly lower sensitivity in adults (about 80–85% vs. >95% for tTG IgA) but higher sensitivity in children under 2. In my clinical experience, I reach for the DGP panel when I suspect celiac disease but the tTG IgA comes back negative, or when a patient has IgA deficiency. In that setting, the DGP IgG component can be a lifesaver—it catches cases that might otherwise be missed.

Can DGP Antibodies Be Elevated in Other Conditions?

Yes, but it is uncommon. A mild elevation can sometimes be seen in dermatitis herpetiformis, non-celiac gluten sensitivity, inflammatory bowel disease, or autoimmune liver disease. However, high levels (e.g., >3 times the upper limit) are highly specific for celiac disease. I always tell my patients: the DGP test is a piece of the puzzle, not the whole picture. It works best when interpreted alongside symptoms, family history, and other lab results.

DGP Testing in Children

Young children present a unique challenge. The classic tTG IgA test may be less reliable in infants and toddlers because their immune system is still maturing. Studies show that DGP IgA and IgG have better sensitivity in children under 2 years of age. In my practice, I often order the DGP panel together with tTG IgA for any child with persistent abdominal pain, poor growth, or chronic diarrhoea. The combined approach helps avoid unnecessary biopsies while minimising missed diagnoses.

How to Prepare for the DGP Antibody Test

The most important preparation is to continue your normal gluten-containing diet for at least 6 weeks before the blood draw. If you have already gone gluten-free, the antibodies may fall, and the test could be falsely negative. No other special preparation—no fasting, no medication adjustments (unless advised by your doctor). Simply show up at the lab, and they will take a small sample from your arm. The results usually come back within a few days.

What Happens After a Positive DGP Test?

If your DGP IgA or IgG comes back positive, the next step is almost always referral to a gastroenterologist for a small bowel biopsy to confirm the diagnosis of celiac disease. Occasionally, if the antibody levels are very high and you have classic symptoms, some guidelines allow a diagnosis without biopsy in children. But for adults, biopsy remains the gold standard. Do not start a gluten-free diet until after the biopsy—going gluten-free too early can heal the gut and lead to a false-negative biopsy.

Frequently Asked Questions

What is the difference between DGP and tTG antibodies?

tTG (tissue transglutaminase) antibodies target the enzyme that modifies gluten, while DGP (deamidated gliadin peptide) antibodies target the modified gluten itself. Both are used for celiac disease screening, but tTG is generally the first-line test. DGP adds value in IgA deficiency, young children, and when tTG is negative but suspicion remains high.

Is the DGP test accurate?

The DGP test has a sensitivity of about 80–90% and specificity over 95% for celiac disease when used appropriately. Accuracy is highest when the test is performed while the patient is on a gluten-containing diet. No test is perfect, but DGP combined with tTG and total IgA gives a very reliable screening.

Do I need to be on a gluten-free diet before testing?

No, you must NOT be on a gluten-free diet before the DGP test. In fact, you need to eat gluten regularly for at least 6 weeks before the blood draw. A gluten-free diet can lower antibody levels and cause a false-negative result, delaying diagnosis.