--a serum protein electrophoresis is designed as a screening test for detection of abnormal proteins int he bloodstream, and is designed more to detect rogue antibodies, or M-proteins (monoclonal antibodies), that may be associated with certain blood diseases, particularly blood cancers such as myeloma or Waldenstrom's.

The more specific test is an immunofixation electrophoresis of both serum and urine, which enumerates the immunoglobulin antibody classes--IgA, IgM, IgG--and looks for any monoclonals.