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 (kappa/lambda) 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 <0.04 for kappa and lambda secretors, respectively, for assessing survival. Survival was 30 months in patients with the kappa/lambda ratio of >57.5 and <0.04 compared to 47 months in patients with the ratio <57.5 and >0.04, indicating that more abnormal serum FLC ratios are associated with poorer survival (p<0.011).

CONCLUSIONS

Despite the limitations of the assay, the results of our study indicate that the FLC assay in combination with serum PE has an increased sensitivity in the diagnosis of MM. Also, baseline measurement of the kappa/lambda ratio provides prognostic information in these same patients.