This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'The most reliable investigation in amyloid disease is- \nSelect and explain. \nA. Immunoglobulin assay, B. Ultrasound, C. Rectal biopsy, D. Urine examination', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The best sites from which to obtain a biopsy specimen in systemic amyloidosis are the abdominal fat\xa0pad and rectal mucosa (approaching 90% sensitivity for fat pad and 73-84% for rectal mucosa)\nWhile some imaging modalities can strongly suggest amyloidosis, a tissue sample showing birefringent material is still the criterion standard.\nThis is definitely the case in terms of cardiac-specific amyloid.\nWhile endomyocardial biopsy is the best confirmatory > test for local cardiac amyloid deposition, it can be very- risk averse and requires a centre of excellence with the full complement of immunohistochemical and molecular-based testing', 'role': 'assistant'}]