Test Summary

Kappa/Lambda Light Chains, Free with Ratio, Urine by turbidimetry provides a sensitive detection and quantitation of free light chains (FLCs) in urine earlier than electrophoresis and immunofixation. Urinary FLCs (uFLCs) are known as Bence-Jones Proteins (BJP).
Abnormal levels of FLCs are commonly produced in a constellation of disorders referred as Plasma Cell Dyscrasia producing monoclonal gammopathies (MG), which constitutes neoplastic growth of plasma cell lines that secrete monoclonal proteins, either as intact immunoglobulins, or isolated light chains as in Light Chain Multiple Myeloma (LCMM). Overproduction and extracellular deposition of FLCs can lead to Light Chain Deposition Disease (LCDD) and AL Amyloidosis.
Measurement and quantitation of uFLCs continues to be part of diagnosis of Plasma Cell Dyscrasia especially oligo-secretory disease and follow-up care for multiple myeloma and as an early indicator of renal damage. Although Urine protein electrophoresis and immunofixation are predominantly used for the determination of BJP, absolute measurement of uFLCs by antibody-based method provide better accuracy and higher sensitivity for the measurement of uFLCs.
International Myeloma Working Group (IMWG) recommends, that serum electrophoresis and immunofixation may not be able to detect light-chain aberrations in patients with oligo-secretory disease, such as light-chain MM. Due to their low molecular weight, serum FLCs (sFLCs) are rapidly cleared by the kidneys. In such cases, the monoclonal burden should be measured in a 24 h urine collection or in the serum by an automated sFLCs immunoassay. The latter having a higher sensitivity to detect and quantify the involved free light chains.
Renal physiology remains the most important issue concerning the use of urine for monitoring FLCs. Absolute measurement of FLCs in urine and serum show insufficient correlation and cannot be considered interchangeable. There is, however, some evidence that uFLCs may have prognostic value in cases where sFLC results have discordance with the clinical picture and screening patients with suspected AL Amyloidosis.

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