Comparison of Serum Immunofixation Electrophoresis and Free Light Chain Assays in the Detection of Monoclonal Gammopathies

Prescilla B. Wood; Yolonda G. McElroy; Marvin J. Stone


Clin Lymphoma Myeloma. 2010;10(4):278-280. 

In This Article

Abstract and Introduction


Background: Diagnosis of monoclonal gammopathies (MGs) is determined by demonstration of a monoclonal immunoglobulin molecule or chain in serum and/or urine. Previous results on immunofixation electrophoresis (IFE) and quantitative free light chain (FLC) measurements have been conflicting.
Patients and Methods: The purpose of this study was to compare IFE with serum FLC assays in the detection of MG. Between November 2006 and November 2007, results on routinely ordered serum IFE specimens were compared with independently conducted FLC assays.
Results: Monoclonal gammopathies were identified in 144 specimens by IFE; 73 patients (50.7%) had a normal κ/λ ratio in the FLC assay. Also, 44.6% of samples with IgG and IgA M-proteins had a normal κ/λ ratio. Of 357 sera that showed no M-protein by IFE, 95.8% exhibited a normal κ/λ ratio. Out of 11 patients with light chain disease, 9 had abnormal κ/λ ratios. It is unclear why half of the patients with MG by IFE had normal κ/λ ratios. Lower M-components in these patients suggested that some had monoclonal gammopathy of undetermined significance.
Conclusion: For screening purposes, serum IFE should be carried out in patients with suspected MG.


Our previous study on light chain disease (LCD) in patients with multiple myeloma (MM) and light chain (AL) amyloidosis indicated that 80% had detectable Bence-Jones proteinemia.1 However, free monoclonal light chains could not be accurately measured. The advent of the serum free light chain (FLC) assay has made quantification possible.[2–4] These assays have become widely available and are used for diagnosis and management of certain patients with monoclonal gammopathies (MGs).[5–7] It is unclear how this new method compares with standard tests for identifying MGs. The purpose of this report is to compare the results of routinely ordered immunofixation electrophoresis (IFE) with independently conducted serum FLC assays in a single laboratory in a hospital that serves as a primary care and referral center.