Specificity of Serum and Urine Protein Electrophoresis for the Diagnosis of Monoclonal Gammopathies

Abstract

To the Editor: Serum protein electrophoresis (SPE)1 is the hub of laboratory testing for monoclonal gammopathies and is a component of almost all diagnostic panels (1–3). The sensitivity of SPE as a screening test, however, is dependent on how SPE abnormalities are defined (4). Discrete, quantifiable electrophoretic bands (M-spikes) are almost always monoclonal proteins. Subtle abnormalities such as fuzzy γ bands, increased β or α fractions, or decreased γ fractions may reflect the presence of a monoclonal protein, or they may have other causes. Because these subtle abnormalities can reflect serious diseases, laboratories often reflex samples with SPE abnormalities to immunofixation electrophoresis (IFE) for confirmation, even if IFE was not ordered. To evaluate the specificity of these reflex triggers, we reviewed IFE results for reflexed protein electrophoresis assays. We performed SPE, urine protein electrophoresis (UPE), and urine IFE with agarose gel reagents on the Helena REP system (Helena Laboratories) and performed serum IFE with Sebia Hydragel reagent sets (Sebia). All SPE assay results that were reflexed between October 1 and November 3, 2008, and all UPE results reflexed between November 1 and November …