Tests for measuring immunoglobulins include quantitative immunoglobulin assays, serum protein fractionation tests, immunoelectrophoresis, and immunofixation electrophoresis. The presence of abnormal immunoglobulins is suspected when abnormal bands are detected in electrophoresis or when discrepant data appear between tests. Abnormal immunoglobulins include heavy chain disease proteins and half-molecule immunoglobulins that show molecular defects. Such abnormal proteins can be molecularly qualified by SDS-PAGE or immunoblotting. Bence Jones proteins with microheterogenicity can also be demonstrated as the migration changes by immunofixation electrophoresis of samples before and after enzyme treatment. Furthermore, after agarose membrane electrophoresis, the protein can be spontaneously transferred to a polyvinylidene difluoride (PVDF) membrane for easy immunoblotting. In other words, electrophoresis can be used for both detection and analysis of abnormal immunoglobulins.