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KMID : 1101320090410040173
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Korean Journal of Clinical Laboratory Science
2009 Volume.41 No. 4 p.173 ~ p.179
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Antigen Excess in Free Light Chain Assay Using the Hitachi 7600 P-module Automatic Chemistry Analyzer
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Cha Kyong-Ho
Kim Sung-Hee
Song Chang-Un
Sim Yang-Bo
Chae Hyo-Jin
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Abstract
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The analysis of serum free light chains (sFLCs) can improve the diagnosis and monitoring of multiple myeloma and other plasma cell dyscrasias. As with other immunoassays, sFLCstests are subject to potential antigen excess and heterophilic antibody interference. We describe 9 cases of sFLCs antigen excess in patients with multiple myeloma using the FreeliteTM Human Kappa and Lambda Free Kits (The Binding Site ltd., Birmingham, UK) and the Hitachi7600 P module turbidimetric system. A total of 1,247 consecutive samples from 250 patients with multiple myeloma were assayed for sFLCs from April to September, 2009. The samples were assayed using an initial dilution of 1:5and subsequent dilutions of 1:50 and 1:100. The same samples were analyzed for the presence of monoclonal gammopathies using serum protein electrophoresis (SPE) and immunofixation electrophoresis (IFE). There were 9 samples (0.72%) of antigen excess with 3 cases of kappa (0.24%) and 6 cases of lambda (0.48%). These cases represents an example of antigen excess or “hook effect” using the serum free light chain assays and mandates high level of attention to falsely low sFLC levels due to antigen excess, especially when it is disaccordant to other assay results or clinical manifestations.
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KEYWORD
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Immunoassay, Serum Free light chains, Antigen excess, Hook effect, Monoclonal gammopathy, Multiple myeloma, Serum Protein electrophoresis, Immunofixation electrophoresis
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