Comparison of free κ and λ light chain immunoassays and total (bound and free) κ and λ light chain immunoassays.

To the editor: We read, with interest, the article by Dr. Zamora-Ortiz, et al. Poor performance of the total kappa/lambda light chain quantification in the diagnosis and follow-up of patients with multiple myeloma on the comparison of the total serum light chain assay (sLC), SPE and IFx for screening patients with a suspected plasma cell disorder. The authors also mention a new diagnostic test, the serum free light chain assay (FreeliteTM, The Binding Site, Inc., San Diego, CA) which, at the time of publication, was not available in Mexico. This situation has recently changed and the test can now be ordered in Mexico (AIMSA Laboratorio). Monoclonal gammopathies arise from uncontrolled proliferation of abnormal clones of plasma cells that leads to overproduction of monoclonal immunoglobulins. The abnormal plasma cells produce intact immunoglobulins, free ? or ? light chains without an associated heavy chain, or both.