[Analysis of monoclonal protein in 72 cases of multiple myeloma].

Serum and urinary monoclonal proteins (M protein) were measured in 72 cases of multiple myeloma (MM) using rate nephelometry. In IgG and IgA types of MM, the level of immunoglobulin (Ig) corresponding to the malignant isotype was significantly higher and that of Ig uncorresponding to the malignant isotype lower than the normal level. The light chain corresponding to the malignant isotype in serum was increased and the light chain uncorresponding to that in serum was decreased either kappa-IgG, IgA types or lambda-IgG, IgA types. Either kappa-LC or lambda-LC type of MM, the serum light chain corresponding to the malignant isotype was in the normal range and uncorresponding to that was decreased, and the corresponding light chain in urine was significantly elevated. Kappa/lambda ratio in serum and urine was all significantly abnormal in IgG, IgA, and LC types of MM. Our data suggest that any quota among kappa light chain > 20 g.L-1 or < 5 g.L-1, lambda light chain > 10 g.L-1 or < 2 g.L-1 in serum and kappa/lambda ratio > 5 or < 0.75 in serum and urine has an important value for diagnosing MM.