Looking to see if anyone else has had similar contradictory SPEP and MASS-FIX findings. I am in the high risk MGUS category since having a rib plasmacytoma in September 2022. My M spike on SPEP was holding steady at about 1.6. I had my every 3-4 month blood work on April 25th that showed my M spike on SPEP rising to 2. A repeat M spike was done a week later in the myeloma specialist's office and came back 1.9. At the same time, my blood work was sent to the Mayo Clinic where a MASS-FIX found the M spike to be 1.3. Has anyone else encountered this? Does this mean that there is another protein source being picked up by the SPEP? I am waiting for my myeloma specialist to get back to me.