Clinical Significance Of Serum Free Light Chain In Multiple Myeloma

Multiple myeloma (MM) is a plasma cell neoplasm that patients have a rapid proliferation of monoclonal B lymphocytes which produce a number of monoclonal Ig and more monoclonal light chains secreted than heavy chains lead to the appearance of numbers of sFLC which may exceed normal value. Immunoglobulin(Ig) is composed of two heavy chains and two light chains. Normal Ig is synthesized and assembled in B cells according to special ratio. Generally speaking, light chain is synthesized a bit faster than heavy chain which results in the existence of some free light chains in serum(sFLC). Normally, the number of sFLC was kept in a suitable scope. MM patients have a rapid proliferation of monoclonal B lymphocytes which produce a number of monoclonal Ig and more monoclonal light chains secreted than heavy chains lead to the appearance of numbers of sFLC which may exceed normal value. If sFLC secretion overruns the absorption capability of kidney unit, it will be excreted in urine known as Bence Jones protein(BJP,M protein). So it is important to test sFLC or uFLC content for MM diagnosis and therapy response. In the new international uniform response critrria for MM 2006, the sFLC assay is included to allow evaluation of MM patients especially for oligo-secretory and non-secretory MM. Now a highly sensitive technology using immuno-nephelometric assay to test sFLC content is being widely used around the world. But it is not reported about sFLC detecting and study in our country, so we detect sFLC by using immuno-nephelometric assay to explore the clinical significance of sFLC in MM diagnosis and therapy response.Objective: To explore the clinical significance of detecting sFLC in MM patients and AL Amyloidosis by detecting sFLC and compare with serum total chains,uFLC,CRP andβ2-MG. Methods and Results: To detect sFLC content in twenty newly diagnosed MM patients and twenty healthy people using immuno-nephelometric assay and all patients were tested for serum total light chains,urine free light chains(uFLC) value using velocity-scattering nephelometric assay at the same time. Immunofixation electrophoresis (IFE)was done in 18 of 20 patients There was a statistically significant difference between MM sFLC content and κ/λratio and normal comparison(P<0.01). Seven patients were measured for sFLC,serum light chains,urine free light chains,serum CRP and serumβ2-MG was tested by enzyme-linked immunosorbent assay(ELISA)before and after therapy. After therapy, sFLC dropped more than Ig, lightchain, CRP andβ2-MG did with a dropping degree difference statistically significant(P<0.05)while the difference was not obvious as uFLC was concerned(P>0.05).It was also observed patients whose sFLC level fell more had a better therapy response. Using IFE and velocity scattering nephelomeric assay to test the sFLC,uFLC and serum total light chain respectively in AL Amyloidosis patients. Four AL Amyloidosis patients had abnormally high sFLC while only two patients's IFE results were positive. Conclusion: Method testing sFLC by immuno-nephelometric assay combined withκ/λratio is valuable for MM diagnosis . sFLC can be used as a MM therapy response factor and there is a relativity between its dropping degree and patients response. sFLC has a higher sensitivity in MM therapy response than total serum chains , CRP andβ2-MG, while corresponding to uFLC. sFLC test can improve the positive ratio of M protein in AL Amyloidosis check.