Serum free light chain immunoassays and their clinical application

Abstract

Measurement of urine free light chains (flc) is important for assessing monoclonal plasma cell diseases. However, since the kidneys metabolize large amounts of flc, urine concentrations may not accurately reflect plasma cell synthesis. From a theoretical viewpoint, serum measurements would be preferable, just as blood glucose measurements are preferable to urine measurements for managing patients with diabetes mellitus. Unfortunately, the development of satisfactory serum flc immunoassays has been hampered by the lack of specific, high-affinity antisera. Recent publications indicate that this situation has now changed. Serum flc have been quantified using routine clinical laboratory instruments and have produced useful diagnostic results in several diseases. Thus, 100% of patients with light-chain multiple myeloma, 75% of patients with nonsecretory myeloma and more than 95% of patients with primary amyloidosis could be diagnosed using serum flc assays. This improvement in disease detection rates and the potential for superior disease monitoring may obviate the need for urine flc tests in most patients with monoclonal plasma cell diseases.