The following is the least useful investigation in multiple myeloma -
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.
ESR
X-Ray
Bone scan
Bone marrow biopsy
Haematology