γ/IgG ratio: role in distinguishing monoclonal spikes from fibrinogen

Serum protein electrophoresis (SPEP) is a standard screening method for detecting monoclonal gammopathies. Presence of fibrinogen, however, can mimic a true monoclonal spike and interfere with accurate monoclonal protein identification. We describe a novel approach for distinguishing fibrinogen spikes from true monoclonal spikes. We classified 600 individual patient samples into four groups: group 1, 58 samples with a fibrinogen spike; group 2, 127 samples with a spike due to a monoclonal gammopathy; group 3, 181 samples with previously established monoclonal gammopathies but resolved posttreatment; and group 4, 234 control samples without monoclonal gammopathies. The value of using a γ regionfraction/IgG ratio in distinguishing fibrinogen from true monoclonal spikes was assessed. The γ/IgG ratio in the fibrinogen group is significantly (P<0.0001) higher than this ratio in the other three groups. A γ/IgG ratio cut‐off value of 1.13 discriminates true monoclonal gammopathies from fibrinogen. Moreover, exclusion of elevated IgA or IgM cases improves the ratio's predictive power. The probability cut‐off is 0.756, corresponding to a γ/IgG ratio of 1 (93% sensitivity, 91% specificity). Using the γ/IgG ratio improves the screening power of SPEP and offers a simple and reliable diagnostic tool for distinguishing fibrinogen spikes from true monoclonal spikes. J. Clin. Lab. Anal. 25:332–336, 2011. © 2011 Wiley‐Liss, Inc.

[1]  R. Elin,et al.  Identification of a spurious band on serum protein electrophoresis induced by ethanol treatment. , 2006, Clinica chimica acta; international journal of clinical chemistry.

[2]  R. Sodi,et al.  Can lithium-heparin plasma be used for protein electrophoresis and paraprotein identification? , 2006, Annals of clinical biochemistry.

[3]  X. Bossuyt,et al.  Ethanol precipitation is not reliable for selectively removing nonmonoclonal peaks seen in the fibrinogen region on capillary zone electrophoresis of serum proteins. , 2004, Clinical chemistry.

[4]  H. Rossmann,et al.  Serum protein electrophoresis: reptilase treatment is superior to ethanol precipitation for specific removal of fibrinogen from heparinized plasma samples. , 2004, Clinical chemistry.

[5]  S. S. Levinson,et al.  Convenient and effective method for removing fibrinogen from serum specimens before protein electrophoresis. , 2003, Clinical chemistry.

[6]  S. Strobel.  The incidence and significance of pseudoparaproteins in a community hospital. , 2000, Annals of clinical and laboratory science.

[7]  S. Maguire,et al.  Protamine sulphate used in combination with thrombin to remove fibrinogen prior to electrophoresis of heparinised plasma. , 1997, British Journal of Biomedical Science.

[8]  B. Kasravi,et al.  Understanding and interpreting serum protein electrophoresis. , 2005, American family physician.

[9]  D. Keren.  CHAPTER 7 – Conditions Associated With Monoclonal Gammopathies , 1994 .

[10]  H. Keller,et al.  [The use of reptilase for electrophoresis of heparinized plasma (author's transl)]. , 1979, Journal of clinical chemistry and clinical biochemistry. Zeitschrift fur klinische Chemie und klinische Biochemie.

[11]  H. Keller,et al.  Vorbehandlung von Heparin-Plasma zur Protein-Elektrophorese mit Reptilase , 1979 .