Useful For

This test is useful in determining if Bence-Jones (free light chain) protein is present in the urine.  Bence-Jones proteins are monoclonal kappa or lambda immunoglobulin light chains, which are not attached to a heavy chain portion of the immunoglobulin molecule.  They may be seen in urine of plasma cell myeloma patients, where a monoclonal heavy chain and light chain, or just a free light chain is being produced.  Bence-Jones protein may occur as a result of protein overload, where high concentrations of serum monoclonal protein appear in the urine.  Free light chains may filter through the glomerulus of the kidney due to their small molecular size, and accumulate in the tubules.  Renal impairment may result from the toxicity of the light chains.  

Polyclonal light chains may be detected, but are not Bence-Jones proteins.  The polyclonal light chains are generated by increased catabolism of polyclonal light chains in the serum.  They may be found in large quantities in autoimmune diseases such as Lupus Erythothematosis and Rheumatoid Arthritis.