When Patients Have Neuropathy: Frequency Of A Positive Immunofixation Electrophoresis (IFE) For Monoclonal Protein When The Serum Protein Electrophoresis (SPEP) Is Negative, The Veteran Affairs Medical Center (VAMC) Experience

Abstract Introduction/Objective Although serum protein electrophoresis (SPEP) is the backbone of testing to determine the presence of monoclonal proteins, immunofixation electrophoresis (IFE) is more sensitive with the ability to pick up fainter bands or bands comigrating with the normal beta protein peak. Given the costs of performing additional IFE and the known increased sensitivity, algorithms for reflex IFE published in the literature have stated that unexplained neuropathy would be an indication for reflex IFE even if the SPEP appears negative in a new patient. However, literature on exactly how many of these reflex IFE’s end up positive is sparse. Therefore, we present the Veteran Affairs Medical Center (VAMC) experience in a veteran population. Methods As part of a quality assurance/improvement project, retrospective Vista/Fileman search of all SPEPs with IFE performed from January 2017 to February 2019 was undertaken to identify all SPEPs/IFE with the standard comment language typically used in patients with neuropathy, namely a preliminary diagnosis of no monoclonal bands on SPEP with an IFE to confirm this diagnosis. All SPEPs and IFEs had undergone review by a pathologist prior to signout which includes a chart review in the computerized patient record system (CPRS) to rule out the documented presence of unexplained neuropathy in new patients who have not previously had IFE workup. Results There were 129 SPEP/IFE cases identified. Of these 129, the overwhelming majority or 123 specimens (95%) were negative on IFE. However, there were 6 specimens (5%) that demonstrated a band on IFE without a band being identified on the SPEP. These bands were in the beta region or very faintly located in the gamma region at or below the limit of detection of the SPEP Conclusion The performance of IFE for patients with unexplained neuropathy would, in the veteran population at the VAMC, identify a monoclonal band in about 1/20 cases. This provides support for the published algorithms advocating for performing IFE on negative SPEP specimens from patients with unexplained neuropathy, as this finding might be important and would otherwise have been missed if just the SPEP was performed alone.