Clinical Use
Serum free light-chain assays have been used in a number of published studies which have indicated superiority over the urine tests, particularly for patients producing low levels of monoclonal free light chains, as seen in nonsecretory multiple myeloma and AL amyloidosis. This is primarily because of the re-absorption of free light chains in the kidneys, creating a "threshold" of light chain production which must be exceeded before measurable quantities overflow into the urine. While there are a number of publications indicating that serum free light chain analysis is preferable to urine analysis at diagnosis, there is currently no consensus on whether urine tests for monitoring should be replaced.
A series of studies, principally from the Mayo Clinic, have indicated that patients with an abnormal free kappa / free lambda ratio have an increased risk of progression to active myeloma from precursor conditions including Monoclonal gammopathy of undetermined significance (MGUS), Smoldering myeloma and solitary plasmacytoma of the bone. Abnormal free light chain production has also been reported to be prognostic of a worse outcome in multiple myeloma and chronic lymphocytic leukaemia.
Read more about this topic: Serum Free Light Chain Measurement