From the Guidelines
Yes, anti-tissue transglutaminase (tTG) antibody is the same as tissue transglutaminase Immunoglobulin A (IgA), as it measures antibodies against tissue transglutaminase, specifically the IgA class of antibodies. This blood test is the primary screening test used to diagnose celiac disease, with high sensitivity and specificity, as shown in a recent systematic review with meta-analysis 1. When someone with celiac disease consumes gluten, their immune system produces these antibodies that attack the enzyme tissue transglutaminase, which is found in the intestines. The test is typically ordered when a patient presents with symptoms suggestive of celiac disease, such as chronic diarrhea, abdominal pain, or unexplained weight loss.
Key Points to Consider
- The American College of Gastroenterology (ACG) recommends IgA anti-tissue transglutaminase (TTG) antibody as the preferred test for diagnosing celiac disease in persons older than two years 1.
- It's essential to note that for accurate results, patients should continue eating gluten-containing foods before testing, as eliminating gluten can cause antibody levels to decrease and potentially lead to false-negative results.
- If total IgA levels are low, additional testing may be needed since an IgA deficiency could affect the reliability of the anti-tTG IgA test, as highlighted in a study on guidelines for the investigation of chronic diarrhea 1.
- A recent systematic review with meta-analysis found that IgA tTG and IgA EMA were the most commonly studied tests for diagnosing celiac disease, with high sensitivity and specificity 1.
Diagnostic Considerations
- The prevalence of celiac disease varies greatly between studies, and the condition is often underdiagnosed in the United States 1.
- Serological testing for celiac disease should be performed before a gluten-free diet is initiated, and IgA anti-tissue transglutaminase (TTG) antibody is the preferred test in persons older than two years 1.
- In younger children, TTG IgA testing should be combined with IgG- and IgA-deamidated gliadin peptides to improve sensitivity 1.
From the Research
Definition and Relationship
- Anti-tissue transglutaminase (tTG) antibody and tissue transglutaminase Immunoglobulin A (IgA) are related but not exactly the same thing.
- Anti-tTG antibodies refer to the immune system's response to tissue transglutaminase, an enzyme that can trigger an immune reaction in people with celiac disease 2.
- Tissue transglutaminase Immunoglobulin A (IgA) is a specific type of antibody that targets tissue transglutaminase and is commonly used as a diagnostic marker for celiac disease 2, 3.
Diagnostic Use
- IgA anti-tTG is a highly sensitive and specific marker for celiac disease, with a positive predictive value of 90% and a negative predictive value of 98% 3.
- The presence of IgA anti-tTG is a reliable indicator for the diagnosis and follow-up of celiac disease 3.
- A high ratio of anti-TTG antibodies can identify patients with significant mucosal damage and villous atrophy, and may potentially replace the need for a duodenal biopsy in some cases 4.
Mechanism and Effects
- IgA anti-tTG antibodies are produced in the small-intestinal mucosa and can be detected in the serum of patients with celiac disease who are consuming gluten 5.
- These antibodies can inhibit intestinal epithelial cell differentiation, induce intestinal epithelial cell proliferation, increase epithelial permeability, and activate monocytes, contributing to the immunopathology of celiac disease 5.