Special Precautions/Comments:

Method: Turbidometry. Calibration: N/A. EQA Scheme:UK NEQAS scheme for Monoclonal Protein Identification. IQC: Commercial preparation.

Interferences: Haemolysis, grossly lipaemic or icteric samples.

Additional Information:

Indication: Over production of the free light chains can be seen in conditions such as monoclonal gammopathy, light chain diseases, non-secretory myelomas, and amyloidosis

Background Information: Immunoglobulins are comprised of two heavy (either G, A, M, D or E) and two light chains (kappa or lambda). In healthy individuals there is a small excess of free light chain (FLC) production with monomers of kappa molecules and dimers of lambda molecules. Serum concentrations of FLCs are dependent on the balance between production and renal clearance [1]. When there is increased polyclonal immunoglobulin production and/or renal impairment, both kappa and lambda FLC concentrations can increase 10- to 20-fold. However, the relative concentration of kappa to lambda, i.e. the kappa/lambda ratio, remains unchanged [2,4]. In contrast, tumours produce a monoclonal excess of only one of the light chains, often with bone marrow suppression of the other light chain, so that kappa/lambda ratios become highly abnormal. Serum FLC measurement can therefore be used to provide a numerical indicator of clonality [1,4]. Guidelines for the management and monitoring of myeloma suggest that serum FLCs may be useful in monitoring free light chain only myeloma [3]. Abnormal FLC levels and ratio can be found in multiple myeloma, Bence Jones proteinuria, non-secretory myelomas, free light chain disease and primary amyloidosis [1]

References: Bradwell AR. Serum free light chain analysis. 5th Edition. 2009. [Ref 1] Hutchison CA, et al. Serum free light chain measurement aids the diagnosis of myeloma in patients with severe renal failure. BMC Neph. 2008. 9(11):1-8. [Ref 2] Smith A, et al. Guidelines on the diagnosis and management of multiple myeloma 2005. Br J Haem. 2006. 132:410-451. [Ref 3] Bradwell AR. Serum free light chain measurements move to centre stage. Clin Chem. 2005. 51:805-807. [Ref 4]

See Also: Immunoglobulins; Bence Jones Protein/ Urine Light Chains (Biochemistry Dept.)

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