Lab Med Online.  2014 Jan;4(1):28-35.

Direct Measurement of Serum Immunoglobulin Heavy and Light Chain Pairs for Identification of Monoclonal Gammopathy and a Performance Comparison with Capillary Electrophoresis

• Kang MG
• Shin MG
• Kim JG
• Jang MJ
• Lee OJ
• Kim HR
• Cho D
• Kim SH
• Kee SJ
• Shin JH
• Suh SP
• Ryang DW

Abstract

BACKGROUND
Determination of monoclonal gammopathy through conventional protein electrophoresis is sometimes difficult because of the presence of large proteins such as haptoglobin and transferrin, which may obscure the results. Ambiguity in an electrophoresis band can give rise to confusion or difficulty in interpretation. The heavy chain/light chain assay (HLC assay) using Hevylite antibody (The Binding Site, UK) has recently been developed for the accurate measurement of monoclonal proteins. We compared the immunotyping (IT) profiles to the immunoglobulin (Ig) heavy/light chain measurements obtained using the HLC assay and observed the ratios between intact Ig kappa and lambda.
METHODS
We collected 35 and 28 sera from patients with suspicious and definitive monoclonal protein, respectively. Then we performed serum protein electrophoresis (SPEP) and IT by Capillarys2 (Sebia, USA). Monoclonal protein production was investigated using Freelite antibody (The Binding Site) and specific Ig(G, A)kappa and Ig(G, A)lambda Hevylite antibodies. The results were analyzed using PASW 18.0 for Windows (IBM, USA).
RESULTS
Direct measurement of Ig heavy/light chains showed discordant IT results for 12 (34.2%) of 35 patients' sera with suspicious SPEP pattern and identical IT results for 28 patients' sera with definitive monoclonal peak in the SPEP results. Overall, the results of the HLC assay and IT showed good agreement (kappa=0.718, P=0.000 by cross-tabulation Gamma, Kappa analysis).
CONCLUSIONS
The results of direct measurement of serum Ig heavy chain/light chain pairs were comparable to those of IT and were helpful for determination of monoclonality in the case of ambiguous electrophoresis results. Measurement of the heavy chain/light chain pair ratio also allowed precise quantification of the monoclonal Igs with ambiguous electrophoresis patterns and identification or discrimination of clonality.

Keyword

Immunoglobulin; Monoclonal gammopathy; Multiple myeloma; Protein electrophoresis

MeSH Terms

Antibodies
Binding Sites
Capillaries*
Discrimination (Psychology)
Electrophoresis
Electrophoresis, Capillary*
Haptoglobins
Humans
Immunoglobulins*
Multiple Myeloma
Paraproteinemias*
Transferrin
Antibodies
Haptoglobins
Immunoglobulins
Transferrin

Figure

• 

  Fig. 1 Schematic diagram and study plan. This study comprised2 phases: in phase I, the laboratory utility of direct measurement of serum immunoglobulin heavy/light chain pairs(the HLC assay) was determined. In phase II, the HLC assay was validated by testing samples showing a definitive monoclonal peak in SPEP and immunotyping. Abbreviations: SPEP, serum protein electrophoresis; MM, multiple myeloma; HLC assay, heavy chain/light chain assay.

• 

  Fig. 2 Linearity results of Hevylite Ig'κ and Ig'λ assays performed using a mixture of normal pooled sera with high concentration controls (simulation test by serial dilution). (A) IgGκ assay, (B) IgGλ assay, (C) IgAκ assay, (D) IgAλ assay.

• 

  Fig. 3 Serial analysis of sera from an IgGκ multiple myeloma patient; a comparison of serum protein electrophoresis (SPEP), total immunoglobulin G (IgG), monoclonal IgG from SPEP densitometry, and HevyliteTM IgG κ:λ ratio. Abbreviations: IgG, immunoglobulin G; κ, kappa; λ, lambda; TCD, thalidomide plus cyclophosphamide plus dexamethasone treatment; auto-PBSCT, autologous peripheral blood stem cell transplantation; Vel, velcade (bortezomib); IT, immunotyping; PR, partial response; CR, complete response; NR, normal range.

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