Will the serum protein electrophoresis test tell me anything that the immunofixation test would not tell me?

Yes.: The ife is very sensitive at finding an abnormal antibody (monoclonal antibody) in blood, but it does not measure the quantity. The spep is less sensitive at finding the monocloprotein protein, but it is a quantitative test, so it answers "how much" monoclonal protein is present. The spep is used to monitor therapy for that reason.

See below: Immunofixation is a more sophisticated test then serum protein electrophoresis re immunoglobulins.