Established guidelines from the International Myeloma Working Group recommend diagnostic screening for patients suspected of plasma cell proliferative disease using
protein electrophoresis (PEL), free light chain measurements and immunofixation electrophoresis (IFE) of serum and urine in certain cases. Plasma cell proliferative disorders are generally classified as
monoclonal gammopathies given most are associated with the excess secretion of a monoclonal
immunoglobulin or M-
protein. In clinical practice, the M-
protein is detected in a patients' serum by the appearance of a distinct
protein band migrating within regions typically occupied by
immunoglobulins. Given each M-
protein is comprised by a sequence of
amino acids pre-defined by somatic recombination unique to each clonal plasma cell, the molecular mass of the M-
protein can act as a
surrogate marker. We established a mass spectrometry based method to assign molecular mass to the
immunoglobulin light chain of the M-
protein and used this to detect the presence of M-
proteins. Our method first enriches serum for
immunoglobulins, followed by reduction to separate light chains from heavy chains, followed by microflow LC-ESI-Q-TOF MS. The multiply charged light chain
ions are converted to their molecular mass and reconstructed peak area calculations are used for quantification. Using this method, we term "monoclonal
immunoglobulin Rapid Accurate Molecular Mass" or miRAMM, the presence of M-
proteins can be reliably detected with superior sensitivity compared to current gel-based PEL and IFE techniques.