[Progress in the management of multiple myeloma introduced by serum free light chain measurement]

New immunoassay has been developed that allows the measurement of serum free light chains (FLC) more sensitive than currently available methods such as immunoelectrophoresis. This assay is useful especially in the diagnosis of BJP type multiple myeloma (MM), oligosecretory and nonsecretory MM. Baseline FLC value is the prognostic indicator of disease progression from MGUS and solitary plasmacytoma to symptomatic MM, and the prognostic factor of MM. In addition, uniform response criteria using FLC assay has been proposed by International Myeloma Working Group. This review summarized the recent information of the serum FLC assay in the diagnosis and management of MM.