This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Medicine
The following is the least useful investigation in multiple myeloma - 
Select and explain. 
A. ESR, B. X-Ray, C. Bone scan, D. Bone marrow biopsy
C: Bone scan
Answer: C: Bone scan 
Explanation: X ray and bone marrow biopsy is usually taken to diagnose Multiple myeloma. Paraproteinemia can cause an elevated ESR even though not specific. But usually bone scan is not done because sensitivity is low when compared to X ray. Reference : Davidson, 23rd Edition, page no : 967.