Serum free light-chain measurements for identifying and monitoring patients with nonsecretory multiple myeloma

Using sensitive, automated immunoassays, increased concentrations of either kappa or lambda flee light chains (and abnormal kappa/lambda ratios) were detected in the sera of 19 of 28 patients with nonsecretory multiple myeloma, Four other patients had suppression of one or both light chains, and the remaining 5 sera had normal or raised free right-chain concentrations with substantially normal kappa/lambda ratios. Six of the patients with an elevated single free light chain, who were studied during follow-up, had changes in disease activity that were reflected by the changes in free light-chain concentrations. It is concluded that quantification of free light chains in serum should prove useful for the diagnosis and monitoring of many patients with nonsecretory myeloma, (Blood, 2001;97: 2900-2902) (C) 2001 by The American Society of Hematology.