High false-positive rate for monoclonal gammopathy using capillary electrophoresis (CAPILLARYS 2) alone

Background: Capillary zone electrophoresis (CZE) is a newer method of performing serum protein electrophoresis and is considered to be faster and more efficient than agarose gel method. We decided to evaluate CZE as an efficient screening tool for monoclonal gammopathies, and we began recommending immunofixation studies in cases with such minor/subtle distortions to avoid missing monoclonal gammopathies. Methods: We evaluated 163 serum protein agarose gel electrophoresis (SPAGE) samples between October and November 2011, and 447 serum protein CZE (SPCZE) samples between January 2012 to February 2012 and August 2012 to September 2012. Results: Immunofixation studies were recommended in 51 of 163 cases (31.3%) performed by SPAGE, and in 274 of 447 cases (61.3%) performed by SPCZE. While using SPAGE, of the 51 cases recommended for immunofixation (24 were performed to date), six cases (25.0%) were positive for monoclonal gammopathy. In contrast, while using SPCZE, of the 274 cases recommended for immunofixation (118 were performed to date), 18 cases (15.2%) were positive for monoclonal gammopathy. Using the SPCZE method, of these 18 cases, five (27.8%) had minor/subtle distortions without obvious peaks. Our recommendation rate for immunofixation studies has thus almost doubled (61.3% vs. 31.3%) with the adoption of SPCZE. Yet, using SPCZE has not translated to detecting more cases of true monoclonal gammopathies. Conclusion: Therefore, we conclude that there is a high false-positive rate for monoclonal gammopathy using CE alone.