[Free light chains assay: Indications and methods]

Abstract

Serum free light chains (sFLC) assay is an important marker in plasma cell dyscrasia. It is thus recommended for the diagnosis of monoclonal gammopathy, together with serum protein electrophoresis and immunofixation. sFLC assay has also a prognostic value and is a criterion for treatment response and relapse of some monoclonal gammopathies. Three assays are currently available in France, the gold standard being the Freelite^® assay, the two others requiring further validation. These three assays are not interchangeable during patient's follow-up. The Freelite^® assay is integrated in the myeloma diagnostic criteria from the International Myeloma Working Group 2014, and has a higher sensitivity than Bence Jones protein test for diagnosis, treatment response and follow-up of light chain myeloma. The Freelite^® assay is the main marker of therapeutic response in light chain amyloidosis and allows to stratify the risk for progression in monoclonal gammopathy of undetermined significance. Some studies have also shown its value in diagnosis of multiple sclerosis and in screening for monoclonal gammopathy in the cases of acute renal failure. The Freelite^® assay is then currently essential in myeloma or amyloidosis, and could be soon extended to the management of autoimmune diseases.

Keywords: Chaines légères libres sériques; Free light chains; Freelite(®); Gammapathie monoclonale; Indications; Monoclonal gammopathy; Pathophysiology; Physiopathologie.