What is the Difference Between tTG IgA and tTG IgG

The key difference between tTG IgA and tTG IgG is that tTG IgA is a test used by doctors to diagnose the celiac disease based on the finding of transglutaminase IgA antibodies in individuals, while tTG IgG is a test used by doctors to diagnose celiac disease based on the finding of transglutaminase IgG antibodies in individuals.

Celiac disease is an immune disorder where the immune system attacks its own tissues when people eat gluten. This damages the small intestine (gut) and causes an inability to take in nutrients. Celiac disease can cause a range of symptoms, including diarrhoea, abdominal pain, and bloating. Tissue transglutaminase is a target autoantigen in celiac disease. This antigen was found to be the antigen recognized by the antibodies (anti-transglutaminase antibodies: IgA, IgG) specific to celiac disease. tTG IgA and tTG IgG are two laboratory tests used to diagnose celiac disease based on the finding of anti-transglutaminase antibodies in individuals.

CONTENTS

1. Overview and Key Difference
2. What is tTG IgA 
3. What is tTG IgG
4. Similarities –  tTG IgA and tTG IgG
5. tTG IgA vs tTG IgG in Tabular Form
6. Summary –  tTG IgA and tTG IgG

What is tTG IgA?

tTG IgA is a test used by doctors to diagnose celiac disease based on the finding of transglutaminase IgA antibodies in individuals. Celiac disease is an autoimmune disease in which the immune system mistakenly detects “gluten” (which is a protein in wheat, barley, rye, and oats) as a foreign invader. This disease affects approximately 1% of the worldwide population. Here, the immune system makes autoantibodies that attack the enzyme tissue transglutaminase (tTG) in the intestine. tTG deamidates the glutamine residues, creating epitopes that increase the binding affinity of the gluten protein to antigen-presenting T cells. This initiates an adaptive immune response.

Figure 01: Stages of Celiac Disease

tTG IgA tests involve the detection of tissue transglutaminase IgA antibodies that are specific for celiac disease. Individuals with moderately to strongly positive results are more like to have celiac disease. These patients should undergo a biopsy to confirm the diagnosis. Furthermore, the treatment for celiac disease is the maintenance of a gluten-free diet. In most patients, a gluten-free diet declines the level of autoantibodies and improves villous atrophy.

What is tTG IgG?

tTG IgG is a test that diagnoses celiac disease based on finding transglutaminase IgG antibodies in individuals. This is specially performed for individuals who are IgA deficient.

Figure 02: Inflammation of the Intestinal Mucosa that Lead to Villous Atrophy

In individuals with moderately to strongly positive results for IgG autoantibodies, the diagnosis of celiac disease is possible. These patients should undergo a biopsy to confirm the diagnosis. However, tTG IgG is less sensitive and less specific when compared to the tTG IgA test.

What are the Similarities Between tTG IgA and tTG IgG?

• tTG IgA and tTG IgG are two laboratory tests for diagnosing celiac disease based on the finding of anti-transglutaminase antibodies.
• Both tests are serological testing.
• They depend on the presence of a specific enzyme called tissue transglutaminase
• Both tests are enzyme-linked immunosorbent assays.
• After performing both tests, patients should undergo a biopsy to confirm a diagnosis.

What is the Difference Between tTG IgA and tTG IgG?

tTG IgA is a test used by doctors to diagnose celiac disease based on the finding of transglutaminase IgA antibodies in individuals, while tTG IgG is a test used by doctors to diagnose celiac disease based on the finding of transglutaminase IgG antibodies in individuals. Thus, this is the key difference between tTG IgA and tTG IgG. Furthermore, tTG IgA is the main serological test for celiac disease, while tTG IgG is not the main serological test for celiac disease and is performed only when patients are deficient in IgA autoantibodies.

The below infographic presents the differences between tTG IgA and tTG IgG in tabular form for side-by-side comparison.

Summary – tTG IgA vs tTG IgG

tTG IgA and tTG IgG are two serological laboratory tests for diagnosing celiac disease based on the finding of anti-transglutaminase antibodies. tTG IgA test diagnoses celiac disease based on the finding of transglutaminase IgA antibodies in individuals. On the other hand, tTG IgG test diagnoses celiac disease based on the finding of transglutaminase IgG antibodies in individuals. So, this is the key difference between tTG IgA and tTG IgG.

Reference:

1. “Celiac Disease Tests.” National Institute of Diabetes and Digestive and Kidney Diseases, U.S. Department of Health and Human Services.
2. Dahlbom, Ingrid, et al. “Immunoglobulin G (IGG) Anti-Tissue Transglutaminase Antibodies Used as Markers for IGA-Deficient Celiac Disease Patients.” Clinical and Diagnostic Laboratory Immunology, American Society for Microbiology, Feb. 2005.

Image Courtesy:

1. “Coeliac Disease” By WikipedianProlific (CC BY-SA 3.0) via Commons Wikimedia
2. “Inflammed mucous layer of the intestinal villi depicting Celiac disease” By Scientific Animations.com – (CC BY-SA 4.0) via Commons Wikimedia

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