Heavy/Light Chain Assay for Monitoring IgA Multiple Myeloma: Digging Out the IgA from the β Region

Multiple myeloma (MM) is a malignant disorder in which plasma cells of a single clone proliferate and accumulate in the bone marrow, leading to bone destruction and bone marrow failure. These abnormal plasma cells secrete monoclonal Ig. It is estimated that 24050 new MM cases will occur in the US in 2014 (1.4% of all new cancer cases), with a median age at diagnosis of 69 years (1).The diagnosis of MM is based on the presence of monoclonal plasma cells, monoclonal Ig, and myeloma-related organ and tissue impairment including bone lesions. Aside from the standard laboratory testing, identification of monoclonal Ig (paraprotein) by serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE) are the current gold standards supported by the International Myeloma Working Group (IMWG) for diagnosis and monitoring therapy (2). SPEP is a simple laboratory technique established in the 1950s, in which serum is applied to a support medium and exposed to an electric current, and the different serum fractions separate into 5 bands: albumin, α1, α2, β, and γ globulin fractions (3). Special attention is given to the γ region, which is mainly composed of IgG. IFE testing, introduced in the 1980s, uses the same protein separation principle as SPEP but also identifies the abnormal Ig present with isotype- and …