Gliadin (De-amidated, DGP) Antibodies -IgG

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Detects antibodies to gliadin.

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Gliadin (De-amidated DGP) Antibodies - IgG: Comprehensive Test Information Guide

Why is it done?
- Test Purpose: Detects IgG antibodies against deamidated gliadin peptides (DGP), which are fragments of gluten protein modified by tissue transglutaminase. This test measures immune system response to gluten in individuals with celiac disease and non-celiac gluten sensitivity.
- Primary Indications: • Screening for celiac disease in symptomatic individuals • Diagnosis of non-celiac gluten sensitivity when tissue transglutaminase (tTG) IgA is negative • Evaluating patients with gastrointestinal symptoms (chronic diarrhea, abdominal pain, bloating) • Assessing dermatitis herpetiformis (a skin manifestation of celiac disease) • Identifying gluten-related disorders in IgA-deficient individuals • Monitoring dietary adherence in diagnosed celiac disease patients
- Typical Timing: • When celiac serology panels are inconclusive • When IgA tissue transglutaminase results are negative but clinical suspicion remains high • In patients with known IgA deficiency • As follow-up testing in diagnostic evaluation of gluten-related disorders • During initial screening when multiple antibody markers are needed for comprehensive assessment
Normal Range
- Reference Values: • Negative: < 15 U/mL (or < 1.0 U/mL depending on laboratory assay) • Borderline: 15-20 U/mL (varies by laboratory) • Positive: ≥ 20 U/mL or > 1.0 U/mL (reference ranges vary by testing methodology) • Units of Measurement: U/mL (Units per milliliter) or numerical ratios depending on assay type
- Result Interpretation: • Negative (< 15 U/mL): No significant antibodies detected; consistent with absence of gluten-related immune response. Patient likely does not have celiac disease or active gluten consumption is not occurring. • Borderline (15-20 U/mL): Results fall in uncertain range; repeat testing may be recommended or clinical correlation needed with other serological markers. • Positive (≥ 20 U/mL): Presence of deamidated gliadin IgG antibodies; indicates immune response to gluten and supports diagnosis of celiac disease or gluten sensitivity, particularly when other markers are negative.
- Important Notes: • DGP IgG is particularly valuable in IgA-deficient patients who may have negative tTG IgA results • Reference ranges vary significantly between laboratories and testing methodologies • Results should always be interpreted in clinical context with symptoms and other serological findings • Total IgG levels should be checked to rule out immunoglobulin deficiency
Interpretation
- Positive DGP IgG Results: • Indicates celiac disease or gluten sensitivity with active gluten consumption • Suggests intestinal immune activation in response to gluten peptides • More specific for celiac disease when accompanied by positive tissue transglutaminase (tTG) IgA or IgG • Strong clinical significance when tTG IgA is negative but DGP IgG is positive (particularly in IgA deficiency) • May appear before intestinal villous atrophy develops • Typically normalized after 12-24 months on strict gluten-free diet
- Negative DGP IgG Results: • Makes celiac disease less likely but does not completely exclude it • Patient is likely not consuming gluten or is early in disease process • Does not rule out dermatitis herpetiformis if clinical presentation is suggestive • Supports absence of gluten-related immune response at time of testing • May require additional investigation with endoscopy and intestinal biopsy if clinical suspicion remains high
- Factors Affecting Results: • Duration on gluten-free diet: Antibodies decline over time; false negatives possible if patient already avoiding gluten • Degree of intestinal damage: More severe villous atrophy usually correlates with higher antibody levels • Timing of testing: Early in disease course, antibodies may be negative despite positive biopsy findings • IgA deficiency: May cause false negatives on tTG IgA but DGP IgG remains detectable • Laboratory methodology: Different assays have varying sensitivity and specificity • Patient age: Antibody levels may vary in pediatric versus adult populations • Concurrent gastrointestinal infections: May temporarily elevate non-specific antibodies
- Clinical Significance Patterns: • Positive DGP IgG + Positive tTG IgA: Classic celiac disease profile; strong diagnostic confirmation • Positive DGP IgG + Negative tTG IgA: Suggests non-celiac gluten sensitivity or IgA-deficient celiac disease • Positive DGP IgG + Normal IgA levels: Indicates celiac disease; warrants intestinal biopsy • Negative DGP IgG + Positive tTG IgA: Typical finding; celiac disease likely; biopsy indicated • Negative DGP IgG + Negative tTG IgA: Celiac disease unlikely unless patient on gluten-free diet • Borderline values: Consider repeat testing and clinical context; may indicate early disease or recent gluten exposure cessation
Associated Organs
- Primary Organ System: • Small intestine (primary site of gluten-induced damage) • Immune system (mucosal and systemic immunity) • Gastrointestinal tract (stomach, small intestine, colon) • Intestinal epithelium and lamina propria (location of immune activation)
- Associated Medical Conditions: • Celiac disease: Autoimmune enteropathy with villous atrophy • Non-celiac gluten sensitivity: Gluten-related symptoms without intestinal damage • Dermatitis herpetiformis: Cutaneous manifestation of celiac disease • IgA nephropathy: Kidney disease associated with gluten sensitivity in some cases • Secondary conditions related to malabsorption: Iron deficiency anemia, osteoporosis, nutritional deficiencies
- Diseases This Test Helps Diagnose: • Celiac disease (particularly in IgA-deficient patients) • Non-celiac gluten sensitivity • Dermatitis herpetiformis • Gluten ataxia (neurological manifestation) • Associated osteoporosis and metabolic bone disease • Secondary gastrointestinal conditions from untreated celiac disease
- Complications of Abnormal Results: • Malabsorption: Impaired absorption of nutrients, vitamins, minerals, and fats • Secondary anemia: Iron, folate, and B12 deficiency • Osteoporosis and osteopenia: Decreased bone mineral density • Dermatological manifestations: Skin rashes and lesions in dermatitis herpetiformis • Neurological complications: Peripheral neuropathy, ataxia, seizures in severe cases • Reproductive complications: Infertility, recurrent miscarriages, intrauterine growth restriction • Increased malignancy risk: Intestinal lymphomas if untreated • Secondary autoimmune disorders: Thyroiditis, type 1 diabetes, other autoimmune conditions
Follow-up Tests
- Recommended Follow-up Testing: • Tissue transglutaminase IgA (tTG IgA): Primary marker for celiac disease confirmation • Total IgA level: To rule out IgA deficiency that could mask disease • Endomysial antibodies (EMA) IgA/IgG: High specificity for celiac disease confirmation • Tissue transglutaminase IgG (tTG IgG): Alternative marker in IgA-deficient patients
- Confirmatory Investigations: • Upper endoscopy with duodenal biopsy: Gold standard for celiac disease diagnosis; assesses intestinal damage • Multiple intestinal biopsies: Typically taken from duodenum and proximal jejunum • Histopathology: Marsh-Oberhuber classification grading of villous atrophy • Immunohistochemistry: Demonstrates increased intraepithelial lymphocytes
- Monitoring Tests for Established Celiac Disease: • Serum tissue transglutaminase IgA: Every 12-24 months to assess dietary adherence • DGP IgG: Serial measurements to monitor gluten avoidance compliance • Tissue transglutaminase IgG: For IgA-deficient patients on follow-up • Frequency: Initial 6-12 months after diagnosis, then annually if stable • Consider repeat testing if symptoms recur or suspected gluten exposure occurs
- Complementary Tests for Associated Conditions: • Complete blood count (CBC): Screen for anemia from malabsorption • Iron studies: Ferritin, iron saturation, TIBC for iron deficiency • Vitamin B12 and folate levels: Screen for macrocytic anemia • Tissue transglutaminase IgA: Baseline and follow-up for diagnosis confirmation • Thyroid function tests (TSH, free T4): Screen for associated thyroiditis • Bone density scan (DEXA): Assess for osteoporosis in long-standing disease • Tissue transglutaminase for IgA nephropathy: If indicated by renal symptoms • Tissue transglutaminase testing in first-degree relatives: For familial screening
- Genetic Testing: • HLA-DQ2 and HLA-DQ8 genotyping: Determines genetic predisposition; useful to rule out celiac disease if negative • Recommended when serology is equivocal or biopsy is declined • Negative HLA testing makes celiac disease very unlikely
Fasting Required?
- Fasting Requirement: No - Fasting is NOT required for DGP IgG antibody testing. Patient may eat and drink normally before blood draw.
- Patient Preparation Instructions: • No specific fasting required before blood collection • Continue normal diet and fluid intake • No dietary restrictions prior to testing • Inform phlebotomist if on anti-inflammatory medications • Schedule test during normal business hours for optimal sample processing • Arrive well-hydrated for easier venipuncture
- Medications: • Medications do NOT need to be held before testing • Immunosuppressive medications should be noted by laboratory (may affect results) • Antihistamines: May be continued without affecting test accuracy • Corticosteroids: Continue as prescribed; notify laboratory of high-dose therapy • Antibiotics: May be continued; inform laboratory if recently started • No medication adjustment required unless specifically instructed by healthcare provider
- Important Considerations for Accurate Testing: • Must be consuming gluten for 4-6 weeks prior to testing for accurate serology results • Test sensitivity increases with continued gluten intake; false negatives possible if patient already on gluten-free diet • Draw blood during morning hours when antibody concentrations are stable • Inform laboratory of any immune deficiencies or immunosuppressive therapy • Specify testing methodology if specific assay type is preferred • Document date of last gluten-containing food for clinical interpretation • Delay testing if patient has acute gastrointestinal illness; retest after recovery • For follow-up testing after diagnosis, gluten avoidance should be maintained; results expected to normalize over 12-24 months

How our test process works!