Serum free light chains: diagnostic and prognostic value in multiple myeloma

Background: Measurement of serum free light chains (FLCs) has recently become available for the diagnosis and monitoring of patients with plasma cell dyscrasias. The aim of this study was to investigate the performance of the serum FLC assay as a tumour marker by comparing FLC concentrations with serum protein electrophoresis (PE) results in the diagnosis of multiple myeloma (MM). In addition, we also evaluated the prognostic value of the baseline serum FLC ratio in patients with MM. Methods: We measured FLC concentrations and calculated the kappa/lambda (κ/λ) FLC ratios for three groups (control, polyclonal gammopathy and MM). Results: The FLC ratio at a cut-off threshold of 2.0 showed higher sensitivity and specificity compared with serum electrophoresis for the diagnosis of MM. We used the median FLC ratio of >57.5 and 57.5 and