Evidence check: tTG IgA in the context of Müdigkeit

The question about tTG IgA in the context of fatigue is not addressed in the provided context. From general medical knowledge, tTG IgA is a well-established serological marker for celiac disease, an autoimmune condition that frequently presents with fatigue, iron deficiency, and nonspecific gastrointestinal symptoms. The evidence for tTG IgA in diagnosing celiac disease is strong (sensitivity ~95%, specificity ~98%). However, fatigue is a very nonspecific symptom; a positive tTG IgA should be confirmed by duodenal biopsy before recommending a gluten-free diet. A negative tTG IgA does not completely rule out celiac disease (especially in IgA deficiency or early stages). The provided DNA information (FADS, PPARA, etc.) has no direct relevance to tTG IgA or celiac disease. For a comprehensive workup of fatigue, additional lab tests (complete blood count, ferritin, vitamin B12, vitamin D, thyroid function) are advisable.