Simon is a 27 year old accountant with a 2 month history of bloody diarrhoea and abdominal pain. He has lost 3 kg of weight over the last few months but has put this down to going to the gym regularly. He often gets bloated eating breads and tends to avoid having too many carbohydrates in his diet as part of his gym training diet. He has no joint pain, urinary symptoms or rash and his appetite remains good. Family history is unremarkable.
Abdominal examination today is normal and vital signs unremarkable. He went to Turkey on holiday 6 months ago and the rest of his household are well.
Which one of the below tests is most likely to help point to his likely diagnosis?