Diagnostic Schema:
I = Plasmacytoma on tissue biopsy
II = Bone marrow with greater than 30% plasma cells
III = Monoclonal globulin spike on serum protein electrophoresis, with an immunoglobulin G (IgG) peak of greater than 3.5 g/dL or an immunoglobulin A (IgA) peak of greater than 2 g/dL, or urine protein electrophoresis (in the presence of amyloidosis) result of greater than 1 g/24 h
a = Bone marrow with 10-30% plasma cells
b = Monoclonal globulin spike present but less than category III
c = Lytic bone lesions
d = Residual normal immunoglobulin M (IgM) level of less than 50 mg/dL, IgA level of less than 100 mg/dL, or IgG level of less than 600 mg/dL