What to watch with tTG IgA and allergy?

tTG IgA (tissue transglutaminase IgA) is a well-established screening test for celiac disease, an autoimmune condition triggered by gluten. It is not a marker for allergy. Allergies, such as wheat allergy, involve IgE antibodies and immediate hypersensitivity. Elevated tTG IgA suggests celiac disease, not an allergic disorder. However, symptoms can overlap (e.g., gastrointestinal distress, fatigue). Important caveats: tTG IgA can be falsely negative in IgA deficiency (common in celiac patients); in such cases, IgG-based tTG or DGP tests should be used. Transient elevations can occur in liver disease, heart failure, infections, or other autoimmune conditions. A positive tTG IgA should be confirmed with endomysial antibodies (EMA) and duodenal biopsy before starting a gluten-free diet. The test is not validated for allergy diagnosis. Evidence: clinical practice guidelines (e.g., ESPGHAN), but no direct sources from the provided context. Always consult a gastroenterologist for interpretation.