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

Maria Teresa Lee, Patrizio Caturegli, Richard L. Humphrey, Richard E. Thompson, Barbara Detrick

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish (US)
Pages (from-to)332-336
Number of pages5
JournalJournal of Clinical Laboratory Analysis
Volume25
Issue number5
DOIs
StatePublished - 2011

Keywords

  • Fibrinogen
  • Monoclonal gammopathy
  • Serum protein electrophoresis (SPEP)

ASJC Scopus subject areas

  • Immunology and Allergy
  • Hematology
  • Public Health, Environmental and Occupational Health
  • Clinical Biochemistry
  • Medical Laboratory Technology
  • Biochemistry, medical
  • Microbiology (medical)

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