Reflexing Suspicious β-Region Findings on Capillary Serum Protein Electrophoresis to Immunofixation or Immunosubtraction for Detecting Monoclonal Proteins

Objectives Monoclonal immunoglobulins (M-proteins) that migrate in the beta region on serum protein electrophoresis (SPEP) are often cloaked by this region's normal constituents. The present study interrogates the utility of using both quantitative and qualitative alterations in beta-region bands for detection of beta-migrating M-proteins. Methods Consecutive SPEP cases analyzed by capillary electrophoresis were searched to identify the initial workup on 1,841 patients with increased total beta regions, suspicious beta-region findings resulting in reflex immunofixation (IFE), or immunosubtraction (ISUB). To augment quantitative information, separate beta 1 and beta 2 measurements were established and retrospectively used to evaluate their sensitivity for M-protein detection. Results We identified M-proteins in 205 (11.1%) cases, including immunoglobulin A (IgA) (54%), IgG (24%), IgM (13%), and free light chain (9%) isotypes. Of the 15 cases flagged by separate beta 1 and beta 2 measurements that were not identified by total beta-region measurement, 1 progressed to myeloma. Of the 56 beta-migrating M-proteins identified by qualitative features but without increase in any of the beta-region measurements, 1 progressed to myeloma. Conclusions A combination of separate measurements for beta 1 and beta 2 regions together with detection of beta-region distortions increase sensitivity for identifying beta-migrating M-proteins via reflex IFE or ISUB.