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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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The following is the least useful investigation in multiple myeloma?
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The correct answer is  Multiple myeloma is associated with negative bone scan or cold lesions. The bone scan measures the osteoblastic activity. In multiple myeloma, the osteoblasts doesn't react much to bone destruction. Bone scans are least useful for diagnosing multiple myeloma because the cytokines secreted by myeloma cells suppress osteoblastic activity. Ref: Harrison's Principles of Internal Medicine, 17th Edition, Page 703-705; 16th / 658, 659; Davidson's principles and practice of Medicine, 20th Edition, Chapter 24, Page 1052-1054