DGP IgG Test · Blood

About 1 in 100 people have celiac disease, yet most go undiagnosed for years. The standard screening blood test, called tTG IgA (tissue transglutaminase IgA), is excellent for most adults, but it has blind spots. It can miss celiac disease in young children under two, in anyone with low IgA (a common immune protein), and in some adults whose results fall in a gray zone. DGP IgG exists to fill those gaps.

DGP IgG (deamidated gliadin peptide IgG) measures a specific type of antibody your immune system produces when it reacts to gluten. Unlike older "gliadin" tests that were imprecise and have been retired, this second-generation test targets a chemically modified form of gluten that your body creates during the disease process itself. That makes it far more accurate, and in certain populations, it catches cases that the primary screening test cannot.

How Your Body Produces DGP IgG

When you eat gluten, your gut breaks it into smaller protein fragments called gliadin peptides. In people with celiac disease, an enzyme in the intestinal lining called tissue transglutaminase (often shortened to tTG or TG2) chemically modifies these fragments through a process called deamidation. The modified fragments are much more visible to the immune system. Your immune cells recognize them as threats and produce antibodies against them.

DGP IgG is one of those antibodies. It belongs to the IgG class, meaning it circulates in your blood regardless of your IgA levels. This is why DGP IgG remains detectable even in people who produce little or no IgA, a situation where the standard tTG IgA test gives falsely reassuring results. A rising DGP IgG level signals that your immune system is actively reacting to gluten in a way that typically accompanies intestinal damage.

Where DGP IgG Adds Diagnostic Value

The primary screening test for celiac disease is tTG IgA, and for most people over age two with normal IgA levels, it works well. DGP IgG becomes valuable in three specific situations where tTG IgA falls short.

• Children under two years old: A meta-analysis of 15 studies covering roughly 6,000 children found that DGP IgG had a pooled sensitivity of 96% and specificity of 96% in this age group. Some biopsy-proven celiac cases that tTG IgA missed were caught by DGP IgG, making it a useful addition to early childhood screening.
• People with IgA deficiency: About 1 in 500 people produce very little IgA, which makes all IgA-based celiac tests unreliable. In a study of 941 participants including IgA-deficient celiac patients, IgG-based tests (DGP IgG and tTG IgG) had comparable sensitivity and are the recommended alternatives.
• Adults with high clinical suspicion but borderline results: In a study of 141 adults undergoing small-bowel biopsy for suspected disease, DGP IgG achieved sensitivity of 96.7% and specificity of 100%, with a near-perfect diagnostic accuracy score of 0.989. Some adults are positive only for DGP IgG when tTG IgA is equivocal.

If you do not fall into one of these categories, tTG IgA alone is usually sufficient. In a large pediatric cohort of 3,555 children, adding DGP testing to tTG IgA would have identified only 0.18% additional celiac cases. The test adds the most when the standard approach has a known limitation.

An Early Warning in At-Risk Children

One of the most interesting findings about DGP IgG comes from prospective studies that follow children with a family history of celiac disease. In a cohort of 325 at-risk children, a rise in DGP IgG preceded the rise in tTG IgA (the standard marker) by roughly 6 to 12 months. About 74% of children who eventually developed celiac disease showed elevated DGP IgG before tTG IgA turned positive.

This suggests DGP IgG can serve as an early signal that a child's immune system is losing tolerance to gluten, before the full autoimmune response to tTG kicks in. For families with a known celiac history, tracking DGP IgG alongside tTG IgA could shorten the diagnostic delay. However, an elevated DGP IgG without a concurrent rise in tTG IgA is not, by itself, a diagnosis. It is a signal that warrants closer monitoring, not immediate lifelong dietary restriction.

DGP IgG and Diet Monitoring

Once celiac disease is diagnosed, the treatment is a strict gluten-free diet. DGP IgG levels typically fall as gluten is removed and intestinal healing occurs. In a study of 119 pediatric celiac cases, all antibody levels (including DGP) declined after six months on a gluten-free diet. Deamidated gliadin antibodies also correlate with the degree of villous atrophy (damage to the finger-like projections lining the small intestine), making them a useful, though imperfect, window into mucosal health.

That said, serology alone is not a reliable proof of perfect diet adherence. A multicenter study of 188 celiac patients on a gluten-free diet found that nearly 30% had detectable gluten fragments in their stool, yet 83% of those with the highest gluten exposure still tested negative on DGP IgA. Small or intermittent gluten exposures may not trigger a measurable antibody rise. If your DGP IgG normalizes, it is encouraging but not a guarantee that your gut has fully healed or that trace gluten is not getting through.

Reference Ranges

DGP IgG is interpreted as a positive or negative result, not as a continuous scale with "optimal" zones. The cutpoint that separates positive from negative depends entirely on the assay your lab uses. There is no single universal threshold.

These ranges come from commonly used commercial assays (primarily INOVA/Quanta Lite platforms) studied in clinical cohorts. They are illustrative orientation for understanding your result, not a substitute for your own lab's reported reference interval.

Compare your results within the same lab over time for the most meaningful trend. Different assay manufacturers use different units, scales, and cutoffs, so a number from one lab cannot be directly compared to a number from another.

When Results Can Be Misleading

Because DGP IgG measures an immune response to gluten, the most common source of a misleading result is gluten avoidance. If you have already started reducing or eliminating gluten before being tested, your DGP IgG may be falsely low or negative, even if you have active celiac disease. For an accurate initial diagnostic test, you need to be eating gluten regularly.

• Gluten-free or low-gluten diet before testing: This is the single biggest confounder. If you have already removed most gluten from your diet, antibody levels drop, and your result may not reflect your true immune status.
• Isolated low-titer positivity in low-risk settings: Some commercial DGP IgG assays can generate false positives, particularly at titers just above the cutpoint, in people who do not have celiac disease and who lack the genetic susceptibility (HLA-DQ2/DQ8). A weakly positive DGP IgG in someone without symptoms or family history should be confirmed with additional testing before any conclusions are drawn.
• Assay variation between laboratories: Different DGP IgG kits use different antigenic targets, scoring systems, and cutoffs. A result from one platform is not interchangeable with a result from another. Always retest at the same lab when tracking your trend.

No published data exist on whether common medications (statins, metformin, corticosteroids, proton pump inhibitors) or acute events (illness, surgery, intense exercise) significantly affect DGP IgG levels. This is a gap in the literature, not evidence that these factors are irrelevant. If you are taking immunosuppressive medications, mention this when interpreting results with a clinician, as any treatment that broadly suppresses antibody production could theoretically lower autoantibody titers.

Tracking Your Trend

A single DGP IgG result tells you whether your immune system is reacting to gluten right now. Serial measurements tell you a much richer story: whether your gluten-free diet is working, whether your intestinal immune response is quieting down, and whether a previously borderline result is trending toward or away from positivity.

If you have been diagnosed with celiac disease, retest DGP IgG (along with tTG IgA if applicable) roughly 6 months after starting a strict gluten-free diet, then annually. A declining trend confirms that the dietary change is reducing the immune response. Persistent positivity after 12 months of strict avoidance warrants investigation for hidden gluten sources or a possible complication like refractory celiac disease.

If you are testing proactively because of a family history of celiac disease, get a baseline while you are still eating gluten. If the result is negative, retest every one to two years, because celiac disease can develop at any age. If you notice a rising trend, even within the "negative" range, that trajectory may be more informative than any single number.

What to Do with an Abnormal Result

A positive DGP IgG does not, by itself, diagnose celiac disease. It is one piece of a diagnostic puzzle. The next steps depend on your full clinical picture.

• If tTG IgA is also positive: This double positivity significantly raises the likelihood of celiac disease. At very high tTG IgA levels (10 times or more above the upper limit of normal), some guidelines allow diagnosis without biopsy in children. Otherwise, an intestinal biopsy via endoscopy is the standard next step.
• If DGP IgG is positive but tTG IgA is negative: Check your total IgA level. If IgA is low, tTG IgA is unreliable and the DGP IgG result carries more weight. Order tTG IgG alongside it. If IgA is normal, an isolated DGP IgG positive with negative tTG IgA has a relatively low positive predictive value (about 15.5% for biopsy-proven celiac in one referral-center series). Retest to confirm, and consider HLA-DQ2/DQ8 genotyping: if those genes are absent, celiac disease is essentially excluded regardless of the antibody result.
• If you are monitoring an existing celiac diagnosis: A persistently positive DGP IgG after a year on a strict gluten-free diet suggests ongoing gluten exposure or, less commonly, refractory disease. A gastroenterologist with celiac expertise can help investigate.

For anyone with a positive result and no prior diagnosis, consultation with a gastroenterologist is the clearest path forward. Do not start a gluten-free diet before completing the diagnostic workup, because removing gluten will lower antibody levels and make subsequent testing and biopsy harder to interpret.