What a Positive Deamidated Gliadin Peptide IgA Test Indicates
A positive deamidated gliadin peptide IgA (DGP-IgA) test strongly suggests celiac disease and requires further evaluation with tissue transglutaminase IgA (tTG-IgA) testing and, in most cases, duodenal biopsy for definitive diagnosis. 1
Understanding the Test Result
A positive DGP-IgA indicates your immune system is producing antibodies against deamidated gliadin, a component of gluten that has been modified by tissue transglutaminase. This immune response is characteristic of celiac disease, though the test alone cannot confirm the diagnosis.
Diagnostic Accuracy
- DGP-IgA has moderate to good sensitivity (62.7-97.7%) and variable specificity (40-70.2%) depending on the population tested 2
- The test performs better in children than adults, with higher sensitivity in pediatric populations 2
- DGP-IgA should not be used as the sole screening test - it is less reliable than tTG-IgA for initial detection 1, 3
What You Must Do Next
Step 1: Confirm with Additional Serology
You need comprehensive celiac serology testing that includes:
- Total IgA level (to rule out IgA deficiency, which causes false negatives) 1
- tTG-IgA (the gold standard serologic test) 1, 3
- Endomysial antibody IgA (EMA-IgA) if tTG-IgA is weakly positive 2
Step 2: Maintain Gluten in Your Diet
Do not start a gluten-free diet before completing diagnostic testing. Removing gluten will cause antibody levels to drop and intestinal damage to heal, making accurate diagnosis impossible 3. You must consume gluten-containing foods (at least three slices of wheat bread daily) throughout the diagnostic process 3.
Step 3: Proceed to Duodenal Biopsy
In adults, duodenal biopsy remains essential for diagnosis regardless of antibody levels 2, 4. The biopsy should include:
- At least 4 biopsies from the distal duodenum
- At least 1 biopsy from the duodenal bulb 5
The only exception is if you have extremely high tTG-IgA (≥10 times upper limit of normal) confirmed with positive EMA-IgA in a second blood sample 2, 5.
Important Caveats and Pitfalls
False Positives Are Common
An isolated positive DGP-IgA with negative tTG-IgA has very low diagnostic value - only 3.9-15.5% of such patients actually have celiac disease 6, 7. This scenario often indicates other gastrointestinal conditions rather than celiac disease 7.
Age-Specific Considerations
- In children under 3 years old, DGP-IgA has better performance (91.7% positive predictive value) and may be more useful than in older populations 8
- In children under 2 years old, DGP antibodies may be transiently positive and disappear without treatment, questioning their specificity 9
IgA Deficiency
If you have selective IgA deficiency (present in 1-3% of celiac patients), your DGP-IgA test will be falsely negative. In this case, IgG-based tests (DGP-IgG or tTG-IgG) must be used instead 10, 1, 11.
Clinical Significance
If celiac disease is confirmed, untreated disease leads to:
- Persistent gastrointestinal symptoms affecting quality of life
- Malabsorption causing nutritional deficiencies
- Increased risk of osteoporosis, infertility, and small bowel cancer 2
- In children with type 1 diabetes, unpredictable blood glucose levels and unexplained hypoglycemia 10
The only effective treatment is lifelong adherence to a strict gluten-free diet 2, which is why accurate diagnosis before dietary changes is critical.
Bottom Line
Your positive DGP-IgA is a red flag requiring immediate gastroenterology referral for complete celiac disease evaluation. Do not self-diagnose or start dietary restrictions until the full diagnostic workup (including biopsy in most cases) is complete. The combination of serology and histology provides the definitive answer about whether you have celiac disease.