Open Accessγ/IgG ratio: role in distinguishing monoclonal spikes from fibrinogen
Author(s) -
Lee Maria Teresa,
Caturegli Patrizio,
Humphrey Richard L.,
Thompson Richard E.,
Detrick Barbara
Publication year - 2011
Publication title -
journal of clinical laboratory analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 50
eISSN - 1098-2825
pISSN - 0887-8013
DOI - 10.1002/jcla.20480
Subject(s) - fibrinogen , monoclonal antibody , monoclonal , serum protein electrophoresis , monoclonal gammopathy , paraproteinemias , medicine , immunology , microbiology and biotechnology , antibody , biology
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.