Why is Tissue Transglutaminase IgA Antibody (anti-tTG) Low?

Tissue transglutaminase IgA antibody (anti-tTG) is an important marker used in the diagnosis of coeliac disease, an autoimmune condition triggered by gluten. Understanding what low levels of this antibody mean can help you interpret your test results and decide on next steps with your healthcare provider.

What is Tissue Transglutaminase IgA Antibody?

Tissue transglutaminase IgA antibody (anti-tTG) is a protein produced by the immune system. It is an autoantibody that targets tissue transglutaminase, an enzyme in the body's own tissues, and people with coeliac disease produce it in response to eating gluten, a protein found in wheat, barley, and rye. In people with coeliac disease, the immune system mistakenly attacks the small intestine when gluten is consumed, and anti-tTG levels typically rise. The typical adult range for anti-tTG is 0 to 7 U/mL. A result less than 7 U/mL is considered negative, while higher values, especially when symptoms are present, suggest coeliac disease. It's important to interpret this test alongside total IgA levels to ensure accuracy.

Causes of Low Anti-tTG Levels

Low levels of anti-tTG, meaning levels below 7 U/mL, generally indicate that coeliac disease is unlikely if symptoms are absent. However, there are a few scenarios where low levels might be present:

• Successful Treatment: If you have been previously diagnosed with coeliac disease and have adhered to a strict gluten-free diet, your anti-tTG levels may decrease as your intestine heals.
• IgA Deficiency: Some individuals have an IgA deficiency, a condition where they produce very low levels of IgA antibodies. This can lead to falsely low anti-tTG results.

Symptoms and Implications of Low Anti-tTG

Low anti-tTG levels themselves do not cause symptoms. However, they are often assessed in the context of symptoms suggestive of coeliac disease, such as abdominal pain, bloating, diarrhea, and fatigue. If your anti-tTG levels are low and you do not have symptoms, it generally suggests that coeliac disease is not present.

How to Interpret Low Anti-tTG Results

If your anti-tTG levels are below 7 U/mL, it is typically considered a negative result for coeliac disease. However, this should always be interpreted in conjunction with total IgA levels. If you have an IgA deficiency, your healthcare provider might recommend additional tests to ensure an accurate diagnosis.

Frequently Asked Questions

What is considered a normal range for anti-tTG levels? The typical adult range for tissue transglutaminase IgA antibody is 0 to 7 U/mL. Levels below 7 U/mL are considered negative.

Can low anti-tTG levels change over time? Yes, low anti-tTG levels can change, especially if you have coeliac disease and follow a gluten-free diet. Successful treatment can lower these levels.

Is a low anti-tTG level a cause for concern? Low anti-tTG levels are not usually a cause for concern if you do not have symptoms of coeliac disease. It often indicates that coeliac disease is unlikely.

What should I do if I have symptoms but low anti-tTG levels? If you have symptoms suggestive of coeliac disease but low anti-tTG levels, consult your healthcare provider for further evaluation, including checking total IgA levels.

When to see a doctor

If you experience symptoms suggestive of coeliac disease, such as chronic diarrhea, abdominal pain, or unexplained weight loss, and your anti-tTG levels are low, it is important to consult a healthcare provider. They can perform further tests to determine if an IgA deficiency or another condition might be affecting your results.

Remember, this information is for educational purposes and any medical decisions should be made in consultation with your healthcare provider.