Immunofixation compared with immunoelectrophoresis for the routine characterization of paraprotein disorders.

The authors prospectively compared immunofixation electrophoresis (IFE) with immunoelectrophoresis (IEP) for the evaluation of paraproteins in 32 patient specimens. They used a simple modification of their existing agarose protein electrophoresis system for IFE. Thirteen specimens (40%) required IFE for paraprotein identification, 18 (56%) were definitive by either method, and 1 (3%) did not show a paraprotein by either method. Low titer and/or avidity with anti-lambda antibody from three of seven suppliers prevented or complicated interpretation of IEP patterns with two of four known lambda paraprotein-containing specimens but had no such effect with IFE. In view of these and various additional technical considerations, the authors suggest IFE for the routine characterization of paraproteins in the serum or urine.