MONOCLONAL GAMMOPATHIES
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References:
MONOCLONAL GAMMOPATHIES
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Monoclonal gammopathies constitute a group of diseases characterized by the proliferation of a single clone of plasma cells that produce a homogeneous monoclonal protein (M-protein). The most common examples include monoclonal gammopathy of unknown significance, multiple myeloma, Waldenstrom’s macroglobulinemia, and primary amyloidosis. Less common diseases include solitary plasmacytoma, POEMS syndrome, heavy-chain disease and immunoglobulin deposition disease. An expert panel of the College of American Pathologists developed the following guidelines for the laboratory evaluation of patients suspected of having one of these conditions.
Serum protein electrophoresis (SPE) with high-resolution agarose gel should be the first test performed. M-protein should be quantitated by densitometry measurement of the M-protein peak.
If an M-protein is present, immunofixation (IFE) should be done to characterize its immunoglobulin heavy and light chain type. IFE does not need to be repeated in the future unless there is a change in a subsequent SPE pattern.
Changes in level of a previously identified M-protein should be monitored by SPE and densitometric quantitation at regular intervals. If asymptomatic and M-protein <1.5 g/dL, repeat annually. If asymptomatic and M-protein 1.5 – 2.5 g/dL, repeat in 3 - 6 months. If M-protein is >2.5 g/dL, repeat in 2-4 months. During treatment, repeat every 1-2 months.
If M-protein is detected in serum, a 24 hour urine specimen should be submitted for electrophoresis. Urine electrophoresis is especially important for patients with hypogammaglobulinemia or monoclonal light chain in serum. The M-protein should be reported in grams per 24 hours.
All patients with plasma cell disorders should have direct measurement of immunoglobulins by nephelometry to determine the level of uninvolved immunoglobulins.
Serum viscosity should be determined when a monoclonal IgM protein level is >4 g/dL or a monoclonal IgG or IgA protein value is >6 g/dL.
Cryoglobulins should be assessed in all patients with an M-protein and specific complications due to cold sensitivity. Cryoglobulin assessment is particularly important for patients with monoclonal IgM proteins.
References
- Keren, DF et al. Guidelines for Clinical and Laboratory Evaluation of Patients with Monoclonal Gammopathies. Arch Pathol Lab Med. 1999;123:106-7.
- Kyle, RA. Sequence of Testing for Monoclonal Gammopathies. Arch Pathol Lab Med 1999; 123:114-18.