Lack of utility of free light chain-specific antibodies in the urine immunofixation test.

The urine immunofixation test is performed to evaluate the presence of Bence Jones proteinuria (monoclonal free light chains in urine) in patients with multiple myeloma or other lymphoproliferative disorders. The commonly used Bence Jones proteinuria detection assay from Sebia Electrophoresis contains 5 antisera: a trivalent cocktail consisting of antibodies directed against the γ, α, and μ heavy chains (GAM); 2 antisera detecting both free and bound κ (F+B κ) and λ (F+B λ) light chains; and 2 antisera detecting only the free κ (F κ) and λ (F λ) light chains of immunoglobulins. The rationale for using the F κ and F λ antisera is that they specifically detect the urinary free κ and λ light chains that may have nephrotoxic potential (1). This is in …