Waldenström's macroglobulinemia laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Laboratory Findings
- The laboratory diagnosis of Waldenström's macroglobulinemia is contingent on demonstrating a significant monoclonal IgM spike and identifying malignant cells consistent with Waldenström's macroglobulinemia (usually found in bone marrow biopsy samples and aspirates).
- General studies include a CBC, red cell indices, platelet count, and a peripheral smear.
- Normocytic normochromic anemia, leukopenia, and thrombocytopenia may be observed. Anemia is the most common finding, present in 80% of patients with symptomatic Waldenström's macroglobulinemia.
- The peripheral smear may reveal plasmacytoid lymphocytes, normocytic normochromic red cells, and rouleaux formation.
- Neutropenia can be found in some patients.
- Thrombocytopenia is found in approximately 50% of patients with bleeding diathesis.
- Chemistry tests include lactate dehydrogenase (LDH) levels, uric acid levels, erythrocyte sedimentation rate (ESR), renal and hepatic function tests, total protein levels, and an albumin-to-globulin ratio. The ESR and uric acid level may be elevated.
- Creatinine is occasionally elevated and electrolytes are occasionally abnormal. Hypercalcemia is noted in approximately 4% of patients.
- The LDH level is frequently elevated, indicating the extent of Waldenström's macroglobulinemia–related tissue involvement.
- Rheumatoid factor, cryoglobulins, direct antiglobulin test and cold agglutinin titre results can be positive.
- Beta-2-microglobulin and C-reactive protein test results are not specific for Waldenström's macroglobulinemia. Beta-2-microglobulin is elevated in proportion to tumor mass.
- Coagulation abnormalities may be present. Prothrombin time, activated partial thromboplastin time, thrombin time, and fibrinogen tests should be performed. Platelet aggregation studies are optional.
- Serum protein electrophoresis results indicate evidence of a monoclonal spike but cannot establish the spike as IgM. An M component with beta-to-gamma mobility is highly suggestive of Waldenström's macroglobulinemia.
- A distinguishing feature of WM is the presence of an IgM monoclonal protein (or paraprotein) that is produced by the cancer cells, and a concurrent decrease in levels of uninvolved immunoglobulins (i.e., IgG and IgA).
- Immunoelectrophoresis and immunofixation studies help identify the type of immunoglobulin, the clonality of the light chain, and the monoclonality and quantitation of the paraprotein.
- High-resolution electrophoresis and serum and urine immunofixation are recommended to help identify and characterize the monoclonal IgM paraprotein.
- The light chain of the monoclonal protein is usually the kappa light chain. At times, patients with Waldenström's macroglobulinemia may exhibit more than one M protein.
- Plasma viscosity must be measured.
- Results from characterization studies of urinary immunoglobulins indicate that light chains (Bence Jones protein), usually of the kappa type, are found in the urine.
- Urine collections should be concentrated.
- Bence Jones proteinuria is observed in approximately 40% of patients and exceeds 1 g/d in approximately 3% of patients.
- Patients with findings of peripheral neuropathy should have nerve conduction studies and antimyelin associated glycoprotein serology