[The Accurate Quantification of Monoclonal Immunoglobulin by A Capillary Electrophoresis System]

The amount of monoclonal immunoglobulin (M protein) distinguishes multiple myeloma (M) from mono- clonal gammopathy of undetermined significance (MGUS) and indicates the effectiveness of treatment for MM. It should be calculated by serum total protein (g/dL) and M peak ratio (%) on the densitometry of se- rum electrophoresis. However, the ordinary method possibly overestimates the amount of M protein, be- cause this method utilizes the area from the baseline of the M peak (baseline method). For the more accu- rate measurement of M protein, in this study, we evaluated a capillary electrophoresis system that enables to extract the proper area of M peak by manual operation (peak method). Three serum samples with positive M protein were mixed with M protein negative serum at various ratio, and the measured values of M protein were compared with the theoretical values for both baseline and peak methods. All the results showed that the peak method gave the values close to the theoretical values compared with the baseline method. Espe- cially, the less M protein positive serum was mixed, the further the values by the baseline method parted from the theoretical one. In conclusion, the peak method using a capillary electrophoresis system should be introduced for the accurate quantification of M protein. [Original].