Automated peak detection, isotyping and quantitation of M-proteins by MALDI-TOF MS for replacement of immunofixation and serum protein electrophoresis

In 2018, the Mayo Clinic Protein Immunology Laboratory switched from immunofixation electrophoresis to a MALDI-TOF MS (Mass-Fix) method for the isotyping of M-proteins with a goal of replacing serum protein electrophoresis (SPEP) later. This study defines the performance characteristics of the MALDI-TOF MS method (Q-Mass-Fix) for simultaneous quantitation and isotyping of M-proteins in conjunction with immunoglobulin quantitation. Utilizing an in-house developed software, retrospective quantitation and isotyping by Q-Mass-Fix of 6395 SPEP M-protein positive samples demonstrated good correlation with >90% of results not needing manual intervention. The assay was linear over a range of 7.5 to 0.004 g/dL with 75% of M-proteins detected at 0.004 g/dL. Thus, Q-Mass-Fix quantitation was superior to our current agarose gel SPEP and suitable for patient care.