[Value of serum free light chains assay in plasma cell disorders]

The identification and quantification of the monoclonal immunoglobulin in Plasma Cell Disorders (PCD) is based on electrophoresis, immunofixation (IFE) and on immunoglobulins nephelometric measurement. Even though the combination of these techniques is highly sensitive, there are two entities which pose a diagnostic challenge: Non-secretory Multiple Myeloma (MM) and Amyloidosis (AL) patients. Furthermore, when it comes to the results, these techniques have a degree of subjective interpretation and the IFE does not provide quantitative results. Within these limitations a new assay capable of quantifying free light chains (FLC) in serum has been developed. This is a great improvement in PCD and its major indication is the diagnosis and monitoring of patients with AL and non-secretory MM. In addition, its use has been recommended in the screening of all gammopathies; in the prognostic evaluation of MM and other PCD; and the definition of the stringent complete response for patients who achieve a complete remission (CR) with negative IFE and a normalized FLC ratio.