Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1011 page)

   Limitations

   Selective deficiency of IgM is a rare immune disorder in association with infection and normal levels of other immunoglobulin isotypes.

IMMUNOGLOBULINS, FREE LIGHT CHAINS, SERUM

   Definition

   Plasma cells do not produce complete immunoglobulin molecules. Instead, they produce the heavy and light chain components separately and then assemble them before secretion into the bloodstream. Because plasma cells usually make slightly more light chain components, there are usually some leftover light chains that are secreted in the blood without being bound to a heavy chain. These are known as serum free light chains (FLCs). Normally, there are only very low levels of free light chains in the blood (serum).

   The Freelite, free kappa and free lambda light chain assays, are a new, highly sensitive aid in the diagnosis and monitoring of patients with multiple myeloma and related plasma cell disorders. The Freelite serum free kappa and free lambda light chain assays are run on serum and not on urine with increased sensitivity over current electrophoretic assays.

   Recent studies have shown that Freelite serum free kappa and lambda light chain assays:

   Detect up to 82% of nonsecretory myeloma

   Detect and monitor AL amyloid patients, including those with no monoclonal protein by immunofixation (IFE)

   Detect and assess response to treatment in >95% of patients with light chain and intact Ig multiple myeloma

   Detect up to 96% of intact immunoglobulin myeloma patients

   Provide an earlier marker of therapeutic response or resistance, compared to whole immunoglobulin/M spike assays

   Evaluate risk of progression to myeloma in patients with monoclonal gammopathy of undetermined significance (MGUS)

   In combination with serum protein electrophoresis or IFE alone, provide the optimal detection rate for all paraproteins