Monoclonal gammopathy of undetermined significance diagnostic study of choice

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Omer Kamal, M.D.[2]

Overview

Study of choice

There is no single gold standard test for the diagnosis of Monoclonal gammopathy of undetermined significance. bone marrow aspiration and biopsy is indicated in all patients with an M-protein ≥1.5 g/dL.

Diagnostic Criteria

Non-IgM MGUS — Non-IgM MGUS (IgG, IgA, or IgD MGUS) is diagnosed by meeting the following three criteria

• Presence of a serum monoclonal protein (M-protein, whether IgA, IgG, or IgD), at a concentration <3 g/dL.
• Fewer than 10 percent clonal plasma cells in the bone marrow.
• The absence of lytic bone lesions, anemia, hypercalcemia, and renal insufficiency related to the plasma cell proliferative process.

IgM MGUS — IgM MGUS is diagnosed by meeting the following three criteria

• Presence of a serum monoclonal protein (M-protein, whether IgA, IgG, or IgD), at a concentration <3 g/dL.
• Fewer than 10 percent clonal lymphoplasmacytic/plasma cells in the bone marrow.
• The absence of end-organ damage such as anemia, constitutional symptoms, hyperviscosity, lymphadenopathy, or hepatosplenomegaly related to the plasma cell proliferative process

Light chain MGUS — Light chain MGUS (LC-MGUS) is diagnosed by meeting the following three criteria

• The presence of an abnormal FLC ratio (ie, ratio of kappa to lambda FLCs <0.26 or >1.65)
• Increased level of the appropriate involved light chain (eg, increased kappa FLC in patients with a ratio >1.65 and increased lambda FLC in patients with a ratio <0.26)
• No monoclonal immunoglobulin heavy chain (IgG, IgA, IgD, or IgM)
• Fewer than 10 percent clonal lymphoplasmacytic cells in the bone marrow
• The absence of lytic bone lesions, anemia, hypercalcemia, and renal insufficiency related to the plasma cell proliferative process.