Normal Deamidated Gliadin Antibody Test Results in Celiac Disease Evaluation
Normal (negative) deamidated gliadin IgA and IgG antibody results, when combined with negative tissue transglutaminase (tTG) IgA and normal total IgA levels, effectively rule out celiac disease and no further celiac-specific workup is needed. 1
Interpretation of Normal Results
Negative deamidated gliadin peptide (DGP) antibodies indicate the absence of the immune response to gluten that characterizes celiac disease. The British Society of Gastroenterology guidelines confirm that negative serology combined with normal intestinal biopsy excludes celiac disease. 2
Key Diagnostic Points
Normal total IgA level confirms that IgA-based antibody tests are valid and not falsely negative due to IgA deficiency, which occurs in 1-3% of celiac disease patients. 1
Deamidated gliadin antibodies have superior diagnostic accuracy compared to conventional gliadin antibodies, with DGP-IgA showing 74% sensitivity and 95% specificity, and DGP-IgG showing 65% sensitivity and 98% specificity. 3
IgG DGP is particularly valuable in IgA-deficient patients, demonstrating 93.6% sensitivity and 99.4% specificity—superior to tTG-IgG testing. 1
Clinical Algorithm for Normal Results
When Normal Results Reliably Exclude Celiac Disease
Patient was consuming adequate gluten (at least 10g daily for 6-8 weeks) before testing. 1, 4
Total IgA level is normal, confirming IgA-based tests are interpretable. 1
tTG-IgA is also negative (<15 U/mL in adults, <20 U/mL in children). 1
No high-risk features present (first-degree relatives with celiac disease, type 1 diabetes, autoimmune thyroid disease). 1
Critical Pitfall to Avoid
Never interpret serologic results if the patient has already reduced or eliminated gluten intake, as this significantly reduces test sensitivity and causes false-negative results. 4 The patient must be consuming gluten-containing foods for 6-8 weeks before testing. 1, 4
When to Pursue Further Testing Despite Normal Serology
If clinical suspicion remains extremely high despite negative serology, proceed to upper endoscopy with at least 6 duodenal biopsies, as seronegative celiac disease exists in a small subset of patients. 1
Specific Indications for Biopsy Despite Normal Serology
Unexplained iron deficiency anemia (celiac disease present in 5% of these patients). 4
First-degree relatives of celiac patients with suggestive symptoms. 1
Persistent symptoms highly suggestive of celiac disease (chronic diarrhea, weight loss, malabsorption). 2
Consider HLA-DQ2/DQ8 testing—absence of both alleles has >99% negative predictive value and definitively rules out celiac disease. 1
Test Performance Characteristics
The sensitivity of DGP antibodies is significantly higher in patients with total villous atrophy (>90%) compared to partial villous atrophy (~70%), meaning normal results are more reliable at excluding severe disease. 3
Comparative Accuracy
IgG DGP shows very high specificity (98.9%), superior to IgA DGP (79.8%) and comparable to IgA tTG (96.6%). 5
Combined IgA tTG and IgG DGP testing provides the best diagnostic accuracy, identifying nearly all celiac disease cases with high specificity. 5
Conventional gliadin antibodies (non-deamidated) confer no additional diagnostic benefit in adult celiac disease screening. 6
Alternative Diagnoses with Normal Celiac Serology
Normal deamidated gliadin antibodies with persistent symptoms suggest non-celiac gluten sensitivity rather than celiac disease. In gluten sensitivity, IgG anti-gliadin antibodies (conventional, not deamidated) may be positive in 56.4% of cases, but DGP, tTG, and endomysial antibodies remain negative. 7
Key Distinguishing Features
Non-celiac gluten sensitivity shows normal or mildly abnormal intestinal mucosa without villous atrophy. 7
Patients with gluten sensitivity lack the specific celiac markers (EmA, tTG, and DGP antibodies). 7
Never initiate a gluten-free diet based on symptoms alone without confirmed celiac disease, as this leads to nutritional deficiencies and unnecessary dietary restrictions. 1