A fairly recently introduced assay. Full characteristics are not known. Detects the presence of free kappa and lambda immunoglobulin light chains in serum but does not detect light chains associated with intact immunoglobulin. Ratio of free kappa/lambda is given.
For use as an adjunct to serum and urine electrophoresis and immunofixation as a diagnostic marker for Multiple Myeloma and other plasma cell dyscrasias. Is not recommended as replacement for Bence Jones assay. Main problem is that free light chain levels due increase in hypergammaglobinaemia associated with autoimmune or infectious disease. However ratio of kappa/lambda should be normal in such cases.
For use as an adjunct to serum and urine electrophoresis and immunofixation as a diagnostic marker in some casesof Multiple Myeloma and other plasma cell dyscrasias. Invaluable in non-secretory myelomas and in light chain associated amyloid. Very useful in light chain myeloma. Of less value in straightforward myeloma. May possibly be of value in identifying MGUS which are progressing to myeloma.
Serum Separator Tube (SST)
Turbidimetry (The Binding Site; Optilite). Freelite Assay.
Assay has some problems with antigen excess and Non-linearity.
Free Kappa: 3.3 – 19.4 mg/L;
Free Lambda: 5.71 – 26.3 mg/L;
k/λ ratio: 0.26 – 1.65
5 – 7 days