This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Amyloidosis, Subject name: Pathology
[{'content': 'The best investigation for the diagnosis of amyloidosis is: \nSelect and explain. \nA. Colonoscopy, B. Rectal biopsy, C. Upper GI endoscopy, D. CT scan', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The histological examination of the biopsy material is the commonest and confirmatory method for the diagnosis in a suspected case of amyloidosis. The sites for the biopsy can be:- Renal tissue Rectum Abdominal fat aspiration Gingiva. The rectum Q is the best site for taking the biopsy in the options provided. However as per Harrison latest edition, the abdominal fat aspirate is currently the best option for systemic amyloidosis.', 'role': 'assistant'}]