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: Medicine
The gold standard for the diagnosis of Wilson disease is: 
Select and explain. 
A. Liver biopsy with quantitative copper assay, B. Serum ceruloplasmin along with free copper estimation, C. 24 hour urine copper quantification, D. Liver biopsy and copper staining
A: Liver biopsy with quantitative copper assay
Answer: A: Liver biopsy with quantitative copper assay 
Explanation: The gold standard for diagnosis is liver biopsy with quantitative copper assays. Affected patients have values > 200 mg/g dry weight of liver tissue. Copper stains are not reliable. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 3188