The tissue transglutaminase IgA (tTG-IgA) test is a blood analysis utilized in identifying celiac disease. It measures specific antibodies produced by the immune system.
Understanding the tTG-IgA Test
The tTG-IgA test detects antibodies that target tissue transglutaminase, an enzyme found in the intestines. In individuals with celiac disease, consuming gluten triggers an immune response where the body mistakenly attacks this enzyme, leading to the production of these antibodies. The tTG-IgA test is widely used as a primary screening tool for celiac disease due to its high sensitivity and specificity. For accurate results, individuals should continue eating gluten before testing.
Interpreting Your tTG-IgA Results
A normal tTG-IgA level generally indicates a decreased likelihood of celiac disease. While reference ranges can vary between laboratories, a negative result is typically less than 4.0 U/mL, and some laboratories may consider levels between 4.0 and 10.0 U/mL as weakly positive. Elevated tTG-IgA levels suggest an immune response and indicate a higher probability of celiac disease. Levels greater than 10.0 U/mL are often considered positive. Very high levels, such as those exceeding 10 times the upper limit of normal, strongly suggest the presence of celiac disease, especially in children, and may sometimes allow for diagnosis without a biopsy.
What Abnormal Results May Indicate
Elevated tTG-IgA levels are primarily associated with celiac disease, an autoimmune condition where gluten ingestion damages the small intestine. These elevated antibodies are a strong indicator, but not a definitive diagnosis. Other conditions can also cause elevated tTG-IgA, including autoimmune diseases like type 1 diabetes, autoimmune liver diseases, and thyroid disorders. Inflammatory bowel diseases or certain medications may also lead to increased levels.
A very low or undetectable tTG-IgA level might point to an IgA deficiency. About 2-3% of individuals with celiac disease also have a total IgA deficiency, meaning their bodies produce insufficient IgA antibodies. This deficiency can lead to a false negative tTG-IgA test result, even if celiac disease is present. In such cases, other tests like deamidated gliadin peptide IgG (DGP-IgG) or tissue transglutaminase IgG (tTG-IgG) are often used to screen for celiac disease.
Next Steps After Testing
Discuss tTG-IgA test results with a healthcare professional. If results are normal, celiac disease is generally unlikely; however, if symptoms persist, further investigation may be considered.
For elevated results, further diagnostic steps are usually necessary to confirm a celiac disease diagnosis. An endoscopy with a small intestine biopsy is often considered the gold standard for confirmation. It is crucial not to begin a gluten-free diet before these confirmatory tests, as it can affect the accuracy of both blood tests and biopsies.
If the tTG-IgA result is low or undetectable, particularly with suspected IgA deficiency, additional tests may be ordered. These can include a total serum IgA test to check for IgA deficiency, followed by IgG-based antibody tests if a deficiency is confirmed. Professional medical guidance is important for interpreting results and determining the appropriate management plan.