Tissue transglutaminase IgA (tTG-IgA) is an antibody found in the blood. It serves as an important diagnostic marker. Its presence and levels offer insights into health conditions, particularly autoimmune responses.
What is Tissue Transglutaminase IgA
Tissue transglutaminase (tTG) is an enzyme present in various tissues, including the small intestine. It repairs cells and tissues by forming protein bonds (cross-linking). tTG also participates in other cellular activities like deamidation, which modifies proteins.
Immunoglobulin A (IgA) is an antibody produced by the immune system. Antibodies identify and neutralize foreign substances like bacteria and viruses. IgA is found predominantly in mucous membranes, such as the digestive tract lining, playing a role in local immunity.
tTG-IgA is an autoantibody. Autoantibodies are mistakenly produced by the immune system, targeting the body’s own tissues or enzymes.
Its Connection to Celiac Disease
Tissue transglutaminase IgA is a biomarker for celiac disease, an autoimmune disorder. In genetically predisposed individuals, consuming gluten (a protein in wheat, barley, and rye) triggers an abnormal immune response.
This immune reaction causes the body to produce tTG-IgA antibodies that target the tTG enzyme in the small intestine. This attacks and damages the small intestine lining. The villi, finger-like projections responsible for nutrient absorption, become flattened or damaged. This damage, known as villous atrophy, impairs nutrient absorption.
The tTG-IgA Blood Test
The tTG-IgA blood test is a common screening tool for celiac disease. It measures tTG-IgA antibody levels in the bloodstream and is often the initial diagnostic step.
For accurate test results, individuals must consume a gluten-containing diet before the blood draw. Removing gluten can decrease antibody levels, potentially causing a false negative. The test shows positive results in a high percentage of celiac disease patients consuming gluten.
Understanding Your Test Results
Interpreting tTG-IgA test results involves understanding what positive, negative, or indeterminate outcomes suggest. A positive result indicates the likely presence of celiac disease, as elevated antibody levels are common. A negative result suggests a decreased probability of celiac disease. An indeterminate result requires further evaluation.
A positive tTG-IgA test result alone does not confirm celiac disease. Further diagnostic steps, such as an intestinal biopsy, are needed to confirm the diagnosis. It involves taking small intestine tissue samples to examine for villous damage.
Testing for total IgA levels alongside tTG-IgA is important. Some individuals have an IgA deficiency, where the body produces insufficient IgA. This can cause a false negative tTG-IgA result, even if celiac disease is present. For those with IgA deficiency, other tests like tTG-IgG or deamidated gliadin peptide (DGP) IgG may be used. Consulting a healthcare professional is important for accurate diagnosis and management.