Serum protein electrophoresis is a test that measures specific proteins in the blood. Electrophoresis separates proteins based on their physical properties. The principal clinical use of an serum protein electrophoresis is to determine which of the globulin proteins is elevated and differentiate monoclonal from polyclonal gammopathies. This differentiation is vitally important because monoclonal gammopathies, which are indicated by evidence of a monoclonal M band on the serum protein electrophoresis, indicate malignant or premalignant conditions.