A 55-year-old woman presents with fatigue and dyspnoea on exertion. Laboratory tests show Hb 84 g/L, MCV 72 fL, ferritin 6 µg/L and low transferrin saturation. She denies menorrhagia. What is the most appropriate next diagnostic step?AStart oral iron and no further investigationsBOrder colonoscopy to evaluate for occult gastrointestinal blood lossCOrder bone marrow biopsyDTest for sickle cell diseaseESchedule CT scan of the abdomen and pelvis onlyCheck my answer