Hemoglobins S, C and E Masquerade as Spurious Monoclonal Bands on Serum Protein Electrophoresis
S Zhang, PJ Howanitz, JH Howanitz, I Gashinsky. SUNY Downstate Medical Center, Brooklyn, NY; Kings County Hospital Center, Brooklyn, NY
Background: Identification and quantification of monoclonal (M) immunoglobulins are critical for diagnosis and monitoring of plasmacytomas. Serum protein electrophoresis (SPE) is used routinely for identification and quantification, and few interferences have been reported. A partially hemolyzed non-hemoglobin A (non-HbA) specimen apparently containing a M-protein on SPE prompted us to examine the migration of commonly occuring abnormal hemoglobins.
Design: Specimens from patients with homozygous Hb SS, CC, and EE were identified using high performance liquid chromatography (Bio-Rad Variant II, Bio-Rad Laboratories, Hercules, CA). Red blood cells (RBCs) were separated from plasma by centrifugation, washed three times in phosphate buffered saline, lysed and mixed with equal volumes of normal control serum. We then used the Helena SPIFE 2000 and corresponding SPE membranes and reagents (Helena Laboratories, Beaumont TX) for electrophoresis of the specimens as well as known control specimens from patients who had IgG kappa, IgA lambda, and IgM kappa monoclonal proteins. The same specimens were subjected to immunofixation electrophoresis (IFE) using the Helena instrument and IFE membranes and reagents. Specimens from patients with heterozygous hemoglobinopathies were treated in the same manner as specimens from patients with homozygous hemoglobinopathies.
Results: Hb SS, Hb CC, and Hb EE each migrated as a unique single protein band in the gamma region of the SPE membrane. IFE results indicated that each single unique protein band in the gamma region did not react with IgA, IgM, IgG, kappa or lambda antiserum. Specimens from heterozygous hemoglobinopathy patients gave similar findings for the variant hemoglobin.
Conclusions: We conclude that hemoglobin S, C, and E migrate in the gamma region on serum protein electrophoresis, react with the protein stain on SPE, but do not react with IFE antiserum against IgG, IgA, IgM, kappa or lambda. We suggest that non-HbA hemoglobins such as S, C, and E in hemolyzed specimens may masquerade as a false M-protein on SPE. We recommend that pathologists interpreting serum protein electrophoresis consider the occurrence of a hemoglobinopathy when hemolysis is present, an apparent monoclonal band is seen on SPE, and the band is not confirmed as an immunoglobulin on IFE.
Monday, March 9, 2009 9:30 AM
Poster Session I Stowell-Orbison/Autopsy Award # 197, Monday Morning