Anti-Gliadin Antibodies (AGA)

What are Anti-Gliadin Antibodies?
Anti-gliadin antibodies (AGA) are autoantibodies that target gliadin, a component of gluten found in wheat and related grains. 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 AGA Test

The AGA test is used for:

• Diagnosing Celiac Disease: It helps in the initial screening for celiac disease, particularly in patients presenting with gastrointestinal symptoms.
• Monitoring Gluten Exposure: AGA levels can be useful in assessing adherence to a gluten-free diet.

When to Conduct the Test

Healthcare providers may recommend an AGA 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-gliadin antibodies are generally considered to be less than 20 U/mL.
• Positive Result: Elevated levels of AGA indicate an autoimmune response consistent with celiac disease. However, it is important to note that positive results can also occur in other conditions or even in healthy individuals.

Clinical Implications

• Sensitivity and Specificity: The sensitivity of AGA testing is lower than that of anti-tissue transglutaminase (anti-tTG) antibodies and anti-endomysial antibodies (EmA). While AGA can indicate gluten sensitivity, it is not as specific for diagnosing celiac disease.
• Role in Diagnosis: Due to its lower specificity, AGA is often used in conjunction with other tests, such as anti-tTG and EmA, to confirm a diagnosis of celiac disease. In recent years, the use of AGA has declined as more specific tests have become available.

Conclusion

Anti-gliadin antibodies play a role in the screening and diagnosis of celiac disease but are less reliable than other serological markers. Their presence can indicate gluten sensitivity but should be interpreted alongside more specific tests for accurate diagnosis and management.

References

1. Clinical Practice Update on Diagnosis and Monitoring of Celiac Disease. American Gastroenterological Association. Link
2. Immunoglobulin G (IgG) Anti-Tissue Transglutaminase Antibodies Used as Markers for IgA-Deficient Celiac Disease Patients. PMC. Link
3. Anti-Tissue Transglutaminase Antibodies Not Related to Gluten Intake. Anales de Pediatría. Link
4. Clinical Utility of Anti-Tissue Transglutaminase Antibodies for Diagnosis and Monitoring of Coeliac Disease in Children and Adolescents. PMC. Link
5. Tissue Transglutaminase Antibody (TTG). South Tees Hospitals NHS Foundation Trust. Link