Evaluation of the Screening Tests for the Diagnosis of Plasma Cell Neoplasm

ABSTRACT

BACKGROUND: Plasma cell neoplasm is diagnosed by performing bone marrow examination, serum- and urine-protein electrophoresis, and quantification of free light chains of immunoglobulins. We characterized and quantified monoclonal proteins typical of different diagnosed conditions to determine the best screening test(s). METHODS: We retrospectively reviewed diagnosis of and the characteristics of monoclonal proteins from 113 patients with monoclonal gammopathy. Monoclonal proteins were detected by agarose-gel electrophoresis and capillary electrophoresis, and if the results were ambiguous, they were confirmed by immunofixation electrophoresis. Free light chains were measured using nephelometry. RESULTS: The concentrations of monoclonal proteins in 113 patients with different conditions were as follows multiple myeloma (MM) (67%), 2.66 (0.87-9.48) g/dL; monoclonal gammopathy of undetermined significance (MGUS) (26%), 0.62 (0.08-2.95) g/dL; lymphoma (3%), 3.65 (1.59-6.54) g/dL; Waldenstrom's macroglobulinemia (2%), 1.99 (1.08-2.90) g/dL; amyloidosis (2%), 0.61 g/dL; and POEMS syndrome (1%), 0.99 g/dL. There was a significant difference in the concentration and kappa/lambda ratio (which was based on the immunetype of the monoclonal proteins) of the monoclonal proteins in patients with MM and MGUS (P<0.001 and P=0.004, respectively). The diagnostic sensitivity of serum-protein electrophoresis, free-light-chain assay, and bone marrow analysis was 87.6%, 84.1%, and 84.5%, respectively. The sensitivity of a combination of 2 or 3 of these tests was higher at 100%. CONCLUSIONS: A combination of protein electrophoresis with immunotyping and serum free-light-chain assay may be the best screening method for detecting monoclonal proteins since its non-invasiveness.