A 48-year-old woman presents with diarrhoea, weight loss and iron deficiency anaemia. Coeliac serology shows markedly elevated tissue transglutaminase IgA. Total IgA is normal. Which is the most appropriate next step to confirm the diagnosis?AStart a strict gluten-free diet immediately without further testingBHLA typing onlyCUpper gastrointestinal endoscopy with duodenal biopsies while she remains on a gluten-containing dietDSmall bowel MRIECapsule endoscopyCheck my answer