Hypercalcemia, SPEP/UPEP interpretation

Thanks Kathy for a great case! This is a person with a chest wall mass who came in with weakness and falls found to have a serum calcium of 16, subsequently diagnosed with multiple myeloma and chest wall plasmacytoma.

Main Points:

  1. ) Anterior mediastinal masses include the terrible T’s (thymus, terrible lymphoma, germ cell (teratoma etc), intrathoracic thyroid)… also other masses such as lipoma, fibroma, hemangioma.
  2. ) As we have discussed previously, the approach to hypercalcemia includes determining the PTH to determine if it is PTH driven or not. Then, if PTH is suppressed, checking other labs such as PTHrP, calcidiol and calcitriol to figure out what is driving the elevated calcium. See here and herefor past blogs about diagnosis and management of hypercalcemia.

Want to learn more?

SPEP/ UPEP interpretation pearls

  • An SPEP (serum protein electrophoresis) or spot UPEP (urine PEP) is a gel electrophoresis technique to separate out serum proteins by size and charge. Since gamma globulins (antibodies) are most negative, they migrate the furthest to the anode.
  • If there is increased gamma globulin first you need to determine if it is monoclonal or polyclonal. A monoclonal gammopathy shows up as an “M-spike” on the light absorption tracing and the test reflexes to immunofixation which involves staining a new gel to determine what kind of antibody or antibody segment is being overproduced “M-protein” or paraprotein.
  • There are known diagnostic criteria for differentiating between MGUS (monoclonal gammopathy of unknown significance) and multiple myeloma; be aware that the differential also includes conditions like amyloidosis, light chain deposition disease, Waldenstrom, POEMS and other rare cancers
  • Obtaining a serum free light chain ratio can also guide whether there may be a monoclonal gammopathy occurring
  • Quantitative immunoglobulins (eg “serum IgG level”) are used for monitoring disease activity; they are measured with a different process and concentrations can not be compared with those obtained with SPEP
  • For more information, here is a great article “Does my patient with a serum monoclonal spike have multiple myeloma?”