A 34-year-old woman presents with chronic diarrhoea, weight loss and iron-deficiency anaemia. She also reports intermittent abdominal bloating. What is the most appropriate initial investigation to confirm suspected coeliac disease?ASerum tissue transglutaminase IgA antibodies with total IgABImmediate gluten-free diet without testingCColonoscopy with random biopsies onlyDHydrogen breath test for lactose intoleranceEPlain abdominal X-rayCheck my answer