Monoclonal Protein on Serum Protein Electrophoresis (M Component)
Monoclonal gammopathy of unknown significance (MGUS)
Low concentration of monoclonal immunoglobulins (LCMI)
Heavy chain disease
Suggested Additional Lab Testing
For multiple myeloma:
In addition to SPEP followed by immunofixation, quantitative serum immunoglobulin should be performed, because the M component must be greater than3 g/dL in the serum.
Bone marrow aspirate may be useful to show that at least 10% of the nucleated blood cells are plasma cells.
Bone marrow biopsy may be useful to show aggregates of plasma cells in focal or diffuse patterns.
CBC often reveals a normochromic normocytic anemia.
Peripheral blood smear often shows RBCs in a stacked or rouleaux formation.
For Waldenstrom macroglobulinemia:
Immunofixation to identify the M component as an IgM immunoglobulin with a quantitative IgM level greater than 3 g/dL
Serum viscosity is usually increased.
Peripheral blood smear often shows RBC aggregates in a rouleaux formation.
For heavy chain disease:
Immunofixation reveals the heavy chain as alpha, gamma, or mu.
Bone marrow examination may be informative.
Quantitative determination of the serum M component to demonstrate that an IgG or IgM monoclonal protein is less than 3.0 g/dL or an IgA monoclonal protein is less than 2.0 g/dL, or that a Bence-Jones protein is less than or equal to 1.0 g in a 24-hour urine specimen
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