Tissue Transglutaminase IgA Can Diagnose Celiac Disease With 98% Accuracy
Tissue transglutaminase IgA (tTG-IgA) is the single best blood test for catching celiac disease. With sensitivity as high as 98% and specificity up to 98% in untreated patients, it rarely gets the diagnosis wrong. But here's the catch most people don't hear about: once you start a gluten-free diet and your numbers drop, a normal tTG-IgA result has less than 50% sensitivity for detecting ongoing intestinal damage. The test that's brilliant at finding celiac disease is surprisingly poor at confirming you've actually healed from it. That gap matters. Understanding what tTG-IgA can and can't tell you at each stage changes how you should interpret your lab results, what follow-up to push for, and when a number on a page doesn't tell the whole story.