Clinical Information

Plasma cell proliferative diseases such as multiple myeloma are defined by the monoclonal expansion of bone marrow plasma cells. The abnormal proliferation of clonal cells in the bone marrow can be identified by a skewed ratio of cells synthesizing kappa or lambda immunoglobulin. In addition, the secreted monoclonal immunoglobulin can usually be identified in serum or urine by protein electrophoresis and immunofixation electrophoresis. These electrophoretic procedures can show restricted immunoglobulin migration, characterize the heavy and/or light chains, and quantitate the monoclonal protein. Some monoclonal proteins, however, are difficult to identify and quantitate by electrophoretic assays. The serum concentration of monoclonal free light chains for example may not be high enough to be recognized or quantitated. Immunoassays that are specific for free light chains,as opposed to light chains bound to heavy chains, can quantitate kappa and lambda free light chains. An abnormal ratio of the free light chains can identify excess clonal plasma cell proliferation and the concentration of the monoclonal free light chain can be determined. Another example of proteins that are difficult to identify and quantitate are monoclonal proteins that are intact immunoglobulins (heavy and light chains) that migrate very broadly in the gamma fraction or migrate within the beta or alpha fractions. Immunoassays that are specific for heavy and light chain pairs (HLC) such as IgG kappa or IgG lambda can quantitate the individual HLC pairs and be used to identify abnormal ratios of the HLC pairs and to quantitate the monoclonal HLC pair.