<prompt> The following is the least useful investigation in multiple myeloma :ESRX-RayBone scanBone marrow biopsy  <response>: Answer is C Bone scan Bone scans are least useful for diagnosis of Multiple Myeloma. Cytokines secreted by myeloma cells suppress osteoblastic activity therefore typically no increased uptake is observed. In multiple myeloma the osteohlastic response to bone destruction is negligible. The bone scan therefore is often normal or may show areas of decreased uptake photopenia.It has been found to be less useful in diagnosis than plain radiography. Ig protein 24 hour is a major ciriteria for diagnosis alignleft height133 width100 Note : Serum M component is most commonly IgG Q IgG 53, IgA 25, IgD I Bence Jones proteins are light chain protein only Q. 