Medical Analysis

Understanding Gliadin Antibodies (IgA & IgG): Advanced Clinical Diagnostic Insights

Gliadin is a crucial component of gluten. Gliadin antibodies play a significant role in the screening of celiac disease by detecting the specific immune response to gluten. Anti-gliadin antibodies (AGAs) are produced in response to gliadin, a prolamin found in wheat, which is encoded by three different alleles: AA, BB, and DD. These antibodies primarily target gliadin-derived peptides, which constitute the main proteins of gluten.

It is important to note that AGAs are not entirely specific for celiac disease, as they can also be found in patients suffering from other gastrointestinal diseases, such as gastritis, gastroenteritis, and inflammatory bowel disease (IBD) [1, 2]. Historically, the introduction of the antitransglutaminase test has caused the AGA test to lose some of its diagnostic value [3, 4]. However, the utilization of synthetic gliadin peptides in ELISA tests to detect AGA—especially in children under 5 years of age—increases diagnostic accuracy remarkably, as the anti-transglutaminase test is more useful in older populations [6, 10, 12]. Furthermore, in patients with known IgA deficiency, the AGA IgG test serves as the only viable positive marker for diagnosis [7, 8, 13, 14].

Pathophysiology and Clinical Manifestations of Coeliac Disease

Gluten-sensitive enteropathy is characterized by the flattening of intestinal villi and subsequent malabsorption, which is caused by the toxic effect of gluten, a prominent wheat protein [1, 2]. The presence of fecal antigliadin antibodies can indicate an immune response occurring within the gut to gluten present in the diet [1].

The underlying pathology in both dermatitis herpetiformis and gluten-sensitive enteropathy (GSE) results from an IgA-dominant autoimmune response directed against transglutaminase molecules [5]. In cases of GSE, the principal target is tissue transglutaminase [3, 5]. Conversely, in dermatitis herpetiformis, there is increasing clinical evidence suggesting that epidermal transglutaminase 3 (TG3) may be the dominant antigen triggering the immune response [5].

Diagnostic Indications for Estimation of AGA

The estimation of AGA is indicated for several conditions, including:

• Celiac Disease [1, 3]

• Non-celiac gluten sensitivity / Non-celiac wheat sensitivity (NCGS/NCWS) [6]

• Cerebellar Ataxia

• Dermatitis Herpetiformis [5]

Detailed Clinical Indications for Medical Testing

Dermatitis Herpetiformis: Clinical Diagnosis

Dermatitis herpetiformis (DH) is often described as the “celiac disease of the skin” and is a cutaneous manifestation of gluten-sensitive enteropathy [5]. Patients with DH consistently present with serum IgA antibodies against both epidermal transglutaminase and tissue transglutaminase [5].

Sample Collection and Laboratory Protocols

For accurate testing, the following protocols must be observed:

• A fasting sample is preferred for testing.

• Serum should be utilized, with 2 to 3 ml of blood collected by venipuncture and transferred to a Plain Tube (red-capped).

• Storage of the sample should be maintained between 2 to 8°C.

• The sample cannot be accepted if it is found to be hemorrhagic, icteric, or grossly lipemic.

Methods of Estimation and Antibody Utility

Laboratory methods for estimation include ELISA, Multiplex Immunoassay, Immunofluorescence Assay (IFA), DOX, and Immunoblot (Western Blot) [6, 12, 13]. Regarding the use of AGA IgA and IgG, IgA is more useful in detecting celiac disease because it is produced in the small intestine, the precise location where gluten causes inflammation and irritation in sensitive individuals [1, 3]. IgG levels are less specific to celiac disease, but they remain useful in diagnosing autoimmune problems, particularly in patients who are deficient in IgA [7, 8, 14]. Clinicians must remember that while IgA is more sensitive for the detection of celiac disease, patients with IgA deficiency will find the IgG test significantly more useful [7, 13, 14].

Standard Reference Ranges for AGA IgA

Standard Reference Ranges for AGA IgG

Clinical Applications and Limitations

Limitations:

In patients with extremely low total IgA values, one cannot reliably interpret the results of Gliadin antibodies [7]. Generally, the sensitivity and specificity of these tests hover around 90% [3, 6]. Furthermore, these tests show lower specificity compared to tTG/EMA markers [3]. Potential false positives may arise from infections or other autoimmune disorders, and false negatives are also possible [1, 2]. Therefore, these tests often require confirmatory intestinal biopsy [3].

For Non-Medicos: A Simple Guide to Understanding Gluten Testing

If you are worried about whether your body reacts poorly to gluten (a protein found in wheat, barley, and rye), you might have heard of the “Gliadin Antibody” test. Here is a simple guide to what this means and why it matters.

• What is the Gliadin Antibody Test?

  When people have celiac disease or gluten sensitivity, their immune system mistakenly attacks parts of their own body after eating gluten [1]. Gliadin is a specific part of gluten. The test looks for “antibodies”—which are like little red flags your immune system creates—to see if your body is fighting off gluten [1, 3].

• Why do Doctors Order This Test?

  • Celiac Disease Screening: It helps doctors see if you have Celiac disease, which causes damage to your gut [1, 3].

  • Checking for Sensitivity: If you feel sick after eating bread or pasta, this test can help identify if your body is sensitive to wheat [6].

  • Family History: If a close relative has celiac disease, you might get tested to see if you are at risk [1].

  • Monitoring: If you have already been diagnosed, the test can show if your levels are going down after you stop eating gluten [3].

• What do the Results Mean?

  Your lab report will show two main types of antibodies: IgA and IgG [13].

  • IgA: This is the most important one for most people because it is made in your gut [1, 3]. If this is high, it is a strong hint that your body is having an inflammatory reaction to gluten.

  • IgG: This is used as a backup, especially for people who do not produce enough IgA naturally [7, 14].

• Important Things to Remember

  • Not Always Definitive: This test is not perfect [3]. Sometimes, it can show a “positive” result even if you have a different stomach issue (like a simple infection) [1].

  • The Gold Standard: Because this blood test isn’t 100% accurate on its own, doctors often perform an “intestinal biopsy” (a small sample of your gut tissue) to be absolutely sure [3].

  • Don’t Stop Gluten Yet: It is very important that you do not stop eating gluten before your test [3]. If you stop eating gluten, your body will stop producing these antibodies, and the test will not be able to find them—leading to a “false negative.” Keep eating your normal diet until your doctor tells you otherwise.

By working closely with your healthcare provider, you can use these results to figure out if your symptoms are truly caused by gluten and take the right steps to feel better.

References:

1. Guandalini, S., & Assiri, A. (2014). Celiac disease: a review. JAMA Pediatrics, 168(3), 272–278. https://doi.org/10.1001/jamapediatrics.2013.3858

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2. Lebwohl, B., Sanders, D. S., & Green, P. H. R. (2018). Coeliac disease. The Lancet, 391(10115), 70–81. https://doi.org/10.1016/S0140-6736(17)31796-8

   Cited by: 4

3. Husby, S., Murray, J. A., & Katzka, D. A. (2019). AGA clinical practice update on diagnosis and monitoring of celiac disease—changing utility of serology and histologic measures: expert review. Gastroenterology, 156(4), 885–889. https://doi.org/10.1053/j.gastro.2018.12.010

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4. Manza, F., Sammartino, C., Nandi, N., Markogiannopoulou, A., Lungaro, L., & Shiha, M. G. (2026). How to diagnose coeliac disease in 2026? Minerva Gastroenterology, 72(1), 60-74. https://doi.org/10.23736/S2724-5985.25.04052-5

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5. Reunala, T., Hervonen, K., & Salmi, T. (2021). Dermatitis herpetiformis: an update on diagnosis and management. American Journal of Clinical Dermatology, 22(3), 329–338. https://doi.org/10.1007/s40257-020-00584-2

   Cited by: 168

6. Rashtak, S., Ettore, M. W., Homburger, H. A., & Murray, J. A. (2008). Comparative usefulness of deamidated gliadin antibodies in the diagnosis of celiac disease. Clinical Gastroenterology and Hepatology, 6(4), 426-432. https://doi.org/10.1016/j.cgh.2007.12.030

   Cited by: 177

7. Kumar, V., Jarzabek-Chorzelska, M., Sulej, J., Karnewska, K., Farrell, T., & Jablonska, S. (2002). Celiac disease and immunoglobulin A deficiency: how effective are the serological methods of diagnosis? Clinical and Vaccine Immunology, 9(6), 1295-1300. https://doi.org/10.1128/cdli.9.6.1295-1300.2002

   Cited by: 178

8. Dahlbom, I., Olsson, M., Forooz, N. K., Sjöholm, A. G., Truedsson, L., & Hansson, T. (2005). Immunoglobulin G (IgG) anti-tissue transglutaminase antibodies used as markers for IgA-deficient celiac disease patients. Clinical and Vaccine Immunology, 12(2), 254-258. https://doi.org/10.1128/cdli.12.2.254-258.2005

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9. Anbardar, M. H., Haghighi, F. G., Honar, N., & Zahmatkeshan, M. (2022). Diagnostic value of immunoglobulin G anti-deamidated gliadin peptide antibody for diagnosis of pediatric celiac disease: a study from Shiraz, Iran. Pediatric Gastroenterology, Hepatology & Nutrition, 25(4), 312. https://doi.org/10.5223/pghn.2022.25.4.312

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10. Amarri, S., Alvisi, P., De Giorgio, R., Gelli, M. C., Cicola, R., Tovoli, F., et al. (2013). Antibodies to deamidated gliadin peptides: an accurate predictor of coeliac disease in infancy. Journal of Clinical Immunology, 33(6), 1027–1030. https://doi.org/10.1007/s10875-013-9888-z

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11. Volta, U., Granito, A., Parisi, C., Fabbri, A., Fiorini, E., Piscaglia, M., et al. (2010). Deamidated gliadin peptide antibodies as a routine test for celiac disease: a prospective analysis. Journal of Clinical Gastroenterology, 44(3), 186–190. https://doi.org/10.1097/MCG.0b013e3181c378f6

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12. Basso, D., Guariso, G., Fogar, P., Meneghel, A., Zambon, C. F., Navaglia, F., et al. (2009). Antibodies against synthetic deamidated gliadin peptides for celiac disease diagnosis and follow-up in children. Clinical Chemistry, 55(1), 150–157. https://doi.org/10.1373/clinchem.2008.110395

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13. Villalta, D., Alessio, M. G., Tampoia, M., Tonutti, E., Brusca, I., Bagnasco, M., et al. (2007). Testing for IgG class antibodies in celiac disease patients with selective IgA deficiency. A comparison of the diagnostic accuracy of 9 IgG anti-tissue transglutaminase, 1 IgG anti-gliadin and 1 IgG anti-deaminated gliadin peptide antibody assays. Clinica Chimica Acta, 382(1-2), 95–99. https://doi.org/10.1016/j.cca.2007.03.028

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14. Mozo, L., Gómez, J., Escanlar, E., Bousoño, C., & Gutiérrez, C. (2012). Diagnostic value of anti-deamidated gliadin peptide IgG antibodies for celiac disease in children and IgA-deficient patients. Journal of Pediatric Gastroenterology and Nutrition, 55(1), 50–55. https://doi.org/10.1097/MPG.0b013e31824703c7

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15. Olen, O., Gudjónsdóttir, A. H., Browaldh, L., Hessami, M., Elvin, K., Liedberg, A. S., et al. (2012). Antibodies against deamidated gliadin peptides and tissue transglutaminase for diagnosis of pediatric celiac disease. Journal of Pediatric Gastroenterology and Nutrition, 55(6), 695–700. https://doi.org/10.1097/MPG.0b013e3182645c54

    Cited by: 4

FAQ’s:

• What are Gliadin antibodies?
  These are immune proteins produced in response to gliadin, a component of gluten found in wheat.

• Are Gliadin antibodies celiac-specific?
  No, they are also found in other conditions like gastritis, gastroenteritis, and inflammatory bowel disease.

• Why use synthetic gliadin peptides?
  Synthetic peptides increase diagnostic accuracy significantly, especially in children younger than five years of age.

• What is Gluten-sensitive enteropathy?
  It is characterized by flattening of intestinal villi and malabsorption caused by toxic effects of gluten.

• Which transglutaminase causes GSE?
  In gluten-sensitive enteropathy, the principal target is tissue transglutaminase molecules.

• How is Dermatitis herpetiformis diagnosed?
  It is considered “celiac disease of the skin” and involves serum IgA antibodies against transglutaminase.

• How is the sample collected?
  Collect 2–3 ml of fasting blood by venipuncture into a plain, red-capped tube.

• Why is IgA more useful?
  IgA is produced in the small intestine, where gluten-induced inflammation and irritation primarily occur.

• When is IgG test used?
  IgG testing is useful for diagnosing autoimmune problems in patients who are selectively IgA deficient.

• What limits AGA test accuracy?
  Limitations include lower specificity than tTG/EMA tests, potential for false positives, and need for biopsy.

Related Tests 

• Tissue Transglutaminase (tTG) Antibodies

• Endomysial Antibodies (EMA)