Tissue Transglutaminase IgG (TTG)

Hormone/ Element

Report in 72Hrs

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No Fasting Required

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Specialized test to assess hormonal, immunological, or biochemical function based on clinical suspicion.

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Tissue Transglutaminase IgG (TTG) - Comprehensive Test Guide

Why is it done?
- Test Purpose: Detects IgG antibodies against tissue transglutaminase, an enzyme present in the small intestine. This test is primarily used to screen for celiac disease and dermatitis herpetiformis.
- Primary Indications: Screening for celiac disease in symptomatic patients, confirmation of celiac disease diagnosis, assessment of dermatitis herpetiformis (skin manifestation of celiac disease), and evaluation of non-responsive celiac disease.
- Clinical Symptoms Prompting Test: Chronic diarrhea, abdominal pain and bloating, failure to thrive in children, unexplained anemia, dermatitis herpetiformis rash, osteoporosis at young age, and autoimmune disorders.
- Typical Timing: Often performed as part of initial celiac screening panels, during routine evaluation for gastrointestinal disorders, or when family history of celiac disease exists. Testing should occur while patient is consuming gluten.
Normal Range
- Reference Values: Less than 1.0 U/mL or <1.0 IU/mL (negative). Reference ranges may vary by laboratory; consult specific lab reference values.
- Units of Measurement: U/mL (Units per milliliter) or IU/mL (International Units per milliliter)
- Interpretation Categories: Negative: <1.0 U/mL (Normal, celiac disease unlikely) Weakly Positive: 1.0-1.5 U/mL (May require further testing and clinical correlation) Moderately Positive: 1.5-3.0 U/mL (Suggests celiac disease, recommend confirmation) Strongly Positive: >3.0 U/mL (Highly suggestive of celiac disease, intestinal biopsy recommended)
- What Normal Results Mean: Negative result suggests absence of celiac disease; however, early disease or IgA deficiency may result in false negatives.
- What Abnormal Results Mean: Positive result indicates presence of TTG-IgG antibodies and raises suspicion for celiac disease, particularly in symptomatic individuals. Dermatitis herpetiformis may also show positive results.
Interpretation
- Negative Result (<1.0 U/mL): Celiac disease is unlikely in symptomatic patients consuming gluten. However, very early disease or selective IgA deficiency may cause false negatives. If clinical suspicion remains high, consider IgA total level testing.
- Weakly Positive (1.0-1.5 U/mL): Borderline result requires clinical correlation and additional testing. Recommend repeat testing in 2-4 weeks and consideration of small intestinal biopsy if clinical symptoms are present.
- Moderately Positive (1.5-3.0 U/mL): Suggests celiac disease; recommend confirmatory testing with small intestinal biopsy. Consider checking endomysial antibodies (EMA-IgG) for additional confirmation.
- Strongly Positive (>3.0 U/mL): Highly suggestive of celiac disease. Small intestinal biopsy is strongly recommended to confirm diagnosis and assess degree of mucosal damage.
- Factors Affecting Results: - Gluten consumption: Test must be performed while consuming gluten for accurate results - IgA deficiency: May cause false negatives; total IgA testing is recommended - Medications: Immunosuppressants may reduce antibody levels - Disease stage: Early disease may show lower antibody levels - Dietary compliance: Gluten-free diet reduces antibody production
- Clinical Significance: TTG-IgG is highly sensitive and specific for celiac disease. When combined with clinical presentation and endoscopic findings, it aids in diagnosis. Serial TTG-IgG levels can monitor disease progression and dietary adherence in established celiac disease.
Associated Organs
- Primary Organ System: Gastrointestinal system, particularly the small intestine where tissue transglutaminase is located in the intestinal mucosa.
- Diseases Associated with Abnormal Results: - Celiac disease (most common) - Dermatitis herpetiformis (skin manifestation of celiac disease) - Non-tropical sprue - Refractory celiac disease - Rarely seen in other autoimmune intestinal conditions
- Potential Complications of Undiagnosed Celiac Disease: - Malabsorption of nutrients leading to anemia, osteoporosis, and growth delays - Intestinal villous atrophy and mucosal damage - Secondary lactose intolerance - Increased risk of gastrointestinal malignancies - Associated autoimmune conditions (thyroid disease, Type 1 diabetes) - Neurological complications (ataxia, neuropathy) - Dental enamel defects - Reduced fertility and adverse pregnancy outcomes
- Related Organ Involvement: Celiac disease can affect multiple organ systems including thyroid, pancreas (Type 1 diabetes risk), liver, bones (osteoporosis), and nervous system.
Follow-up Tests
- Confirmatory Tests After Positive TTG-IgG: - Endomysial Antibodies (EMA-IgG): Highly specific confirmatory test - Small Intestinal Biopsy: Gold standard for celiac disease diagnosis; assesses villous atrophy degree - Total IgA Level: Rules out selective IgA deficiency (common in celiac disease)
- Screening Tests for Associated Conditions: - Thyroid Function Tests (TSH, Free T4): Screen for autoimmune thyroiditis - Fasting Glucose/HbA1c: Screen for Type 1 diabetes - Tissue Transglutaminase IgA (TTG-IgA): Primary screening test - Deamidated Gliadin Peptide Antibodies (DGP-IgG/IgA): Additional serology
- Nutritional and Bone Assessment Tests: - Complete Blood Count (CBC): Assess for anemia - Iron Studies (serum iron, ferritin, TIBC): Evaluate iron malabsorption - Vitamin B12 and Folate Levels: Check for deficiency - Comprehensive Metabolic Panel: Assess overall nutritional status - Bone Density Scan (DEXA): Screen for osteoporosis/osteopenia
- Monitoring Schedule for Established Celiac Disease: - TTG-IgG Levels: Repeat every 6-12 months initially to confirm response to gluten-free diet - Annual Repeat Testing: Monitor long-term dietary adherence and disease control - Repeat Endoscopy: Consider 1-2 years after diagnosis to confirm mucosal healing
- Related Complementary Tests: - Tissue Transglutaminase IgA (TTG-IgA): Typically positive in celiac disease - Anti-Endomysial Antibodies IgA: Alternative confirmatory serology - HLA-DQ2/DQ8 Typing: Genetic testing for risk assessment (if diagnosis unclear) - Tissue Transglutaminase IgM: May be positive in early or seronegative disease
Fasting Required?
- Fasting Requirement: No - Fasting is NOT required for TTG-IgG testing. Blood can be drawn at any time of day.
- Gluten Consumption Requirement: IMPORTANT - Patient should continue consuming gluten-containing foods for at least 4-6 weeks prior to testing. Gluten-free diet may result in false-negative results.
- Medications to Report: Inform laboratory of immunosuppressive medications (corticosteroids, biologics) as these may affect antibody levels and test results.
- Patient Preparation Instructions: - No special fasting required; eat and drink normally - Wear comfortable, loose-fitting clothing to facilitate blood draw - Inform healthcare provider of current medications and supplements - Bring insurance card and identification - Inform laboratory staff of any bleeding disorders or blood draw anxiety
- Critical Pre-Test Considerations: - Do NOT start gluten-free diet before testing - Ensure gluten intake is adequate (multiple servings daily for 4-6 weeks) - If already on gluten-free diet, consider reintroducing gluten with physician approval - Avoid antibiotics 2 weeks before test if possible (may affect gut antibody production) - Continue all other medications unless otherwise instructed
- Special Circumstances: For patients with severe symptoms or those unable to consume gluten due to medical reasons, discuss alternative testing approaches with physician. IgA deficient individuals may require TTG-IgG testing as primary screening instead of TTG-IgA.

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