A tTg test, or tissue transglutaminase IgA test, is a blood test primarily used to help doctors diagnose celiac disease.
Here's a more detailed explanation:
What is the tTg Test Measuring?
- Tissue Transglutaminase (tTg): This is an enzyme in the body. In individuals with celiac disease, the immune system produces antibodies against this enzyme when gluten is ingested.
- IgA Antibodies: IgA (immunoglobulin A) antibodies are a type of antibody found in the blood. The tTg test specifically looks for IgA antibodies that are directed against tissue transglutaminase. Elevated levels of these antibodies strongly suggest celiac disease.
How Does it Help Diagnose Celiac Disease?
Celiac disease is an autoimmune disorder where the ingestion of gluten (a protein found in wheat, barley, and rye) triggers an immune response in the small intestine. This response damages the lining of the small intestine, hindering the absorption of nutrients.
When someone with celiac disease consumes gluten, their immune system mistakenly attacks tTg, producing IgA antibodies against it. The tTg test detects these antibodies in the blood.
Important Considerations:
- IgA Deficiency: Some individuals have a general IgA deficiency. In such cases, a tTg-IgA test may give a false negative result. For these individuals, a tTg-IgG test (which measures IgG antibodies instead of IgA) may be more appropriate.
- Accuracy: The tTg-IgA test is highly sensitive and specific for celiac disease, especially when combined with other diagnostic tools.
- Gluten Consumption: It's important to continue consuming gluten before the tTg test is performed. If gluten is eliminated from the diet prior to testing, antibody levels may decrease, potentially leading to a false negative result.
- Follow-up Testing: A positive tTg test typically necessitates further evaluation, including an endoscopy with a biopsy of the small intestine, to confirm the diagnosis of celiac disease.
In Summary
The tTg test is a valuable tool in the diagnostic process for celiac disease, detecting specific antibodies produced by the immune system in response to gluten consumption.
