Anti-Tissue Transglutaminase (Anti-tTG)

What are Anti-Tissue Transglutaminase (Anti-tTG)?
Anti-tissue transglutaminase (anti-tTG) antibodies are autoantibodies that target tissue transglutaminase, an enzyme involved in the deamidation of gluten proteins. The presence of these antibodies is primarily associated with celiac disease, an autoimmune disorder characterized by an inappropriate immune response to gluten, leading to intestinal damage.

Purpose of the Anti-tTG Test

The anti-tTG test is used for:

• Diagnosing Celiac Disease: It is a key serological marker for diagnosing celiac disease, especially in patients presenting with gastrointestinal symptoms.
• Monitoring Adherence to Gluten-Free Diet: The levels of anti-tTG antibodies can help assess whether patients are adhering to a gluten-free diet and monitor disease activity.

When to Conduct the Test

Healthcare providers may recommend an anti-tTG test when patients exhibit symptoms such as:

• Chronic diarrhea
• Abdominal pain and bloating
• Weight loss
• Fatigue
• Dermatitis herpetiformis (a skin manifestation of celiac disease)

Testing Procedure

• Sample Collection: A blood sample is drawn from a vein in the arm.
• Preparation: No special preparation is typically required before the test.

Interpreting Results

• Normal Values: Normal levels of anti-tTG antibodies are generally considered to be less than 7 U/mL.
• Positive Result: Elevated levels of anti-tTG antibodies indicate an autoimmune response consistent with celiac disease. Sensitivity for diagnosing celiac disease with anti-tTG IgA antibodies is reported to be over 90%, with specificity also exceeding 90% when using recombinant human tTG as the antigen.

Clinical Implications

• High Specificity for Celiac Disease: Anti-tTG antibodies are highly specific for celiac disease, but positive results can occasionally occur in other conditions, such as liver diseases or autoimmune disorders.
• IgA Deficiency Considerations: Since some individuals may have IgA deficiency (common in about 1 in 500 people), it is important to measure total IgA levels. In cases of IgA deficiency, testing for IgG anti-tTG antibodies is recommended.

Conclusion

Anti-tissue transglutaminase antibodies are essential in diagnosing and managing celiac disease. Their presence not only confirms the diagnosis but also aids in monitoring dietary adherence and disease activity over time.

References

1. Clinical Utility of Anti-Tissue Transglutaminase Antibodies for Diagnosis and Monitoring of Celiac Disease. PMC. Link
2. Immunoglobulin G (IgG) Anti-Tissue Transglutaminase Antibodies Used in IgA-Deficient Patients. PMC. Link
3. Anti-Tissue Transglutaminase Antibodies Not Related to Gluten Intake. Anales de Pediatría. Link
4. Tissue Transglutaminase Antibody (TTG). South Tees Hospitals NHS Foundation Trust. Link