Do you check beta 2 microglobulin in patients with MGUS?  

I think this question can be answered in two ways - firstly, from the vantage point of clinical utility, and secondly, from the vantage point of cost-effectiveness. I think the short answer to both is no.   For patients with suspected smoldering MM awaiting bone marrow biopsy, PET-CT, wbMRI, ...