Anti-tissue transglutaminase (anti-tTG) refers to specific proteins produced by the immune system, known as antibodies. These antibodies are measured through a blood test to provide insights into immune responses and a person’s health status.
What is Anti-Tissue Transglutaminase?
Tissue transglutaminase (tTG) is an enzyme naturally found in various tissues throughout the body, including the small intestine. It plays a role in cellular processes such as cell adhesion, wound healing, and tissue repair by cross-linking proteins, which helps maintain tissue structure and integrity. Anti-tTG antibodies are autoantibodies, mistakenly produced by the immune system against the body’s own tTG enzyme. Their presence indicates an immune response where the body’s defense mechanisms are targeting its own tissues.
Purpose of the Anti-tTG Test
The anti-tTG test is widely used to screen for celiac disease, an autoimmune condition triggered by consuming gluten. In individuals with celiac disease, the immune system reacts abnormally to gluten, a protein found in wheat, barley, and rye. This reaction leads to the production of anti-tTG antibodies, which then attack the tTG enzyme, particularly in the small intestine. This immune attack damages the small intestine lining, impairing nutrient absorption. The anti-tTG IgA antibody test is a sensitive and specific initial screening tool, providing a non-invasive way to detect this immune response.
Understanding Your Test Results
Anti-tTG test results are typically reported in units per milliliter (U/mL), with interpretation depending on the laboratory’s specific reference range. A normal anti-tTG IgA level is generally considered less than 4.0 U/mL or 10.0 U/mL. Some laboratories classify results between 4.0 and 10.0 U/mL as “weak positive” or “equivocal,” while levels above 10.0 U/mL are considered “positive.”
Elevated anti-tTG levels indicate a heightened likelihood of celiac disease. Higher antibody levels generally correlate with a greater probability of the condition, with very high levels being strongly indicative. Test results can vary between laboratories due to different testing methods and reference ranges.
A small percentage of individuals with celiac disease may have normal anti-tTG IgA levels, especially if they have IgA deficiency. In such cases, other antibody tests (like IgG) may be used. A healthcare professional should interpret test results in the context of a person’s symptoms and medical history.
Next Steps for Abnormal Results
If anti-tTG levels are elevated, further diagnostic tests typically confirm a celiac disease diagnosis. The primary confirmatory test is an intestinal biopsy, performed during an endoscopy. During this procedure, a doctor examines the small intestine lining and collects tissue samples for microscopic examination to check for damage, such as villous atrophy.
Patients should maintain a gluten-containing diet until all diagnostic tests are completed. Avoiding gluten before testing can cause the small intestine to heal and antibody levels to decrease, potentially leading to inaccurate or false-negative results. If a person has already adopted a gluten-free diet, a “gluten challenge” might be recommended, reintroducing gluten for a period before testing.
Following a confirmed diagnosis, a healthcare professional guides the individual in managing celiac disease by adopting a strict, lifelong gluten-free diet. A dietitian specializing in gluten-free diets can provide guidance on dietary changes and nutritional needs. Regular follow-up appointments and monitoring of antibody levels are important to assess diet effectiveness and overall health.