Immunoglobulin Heavy/Light Chain Quantification – Update on a New Biologic Marker in IgA Multiple Myeloma

Research Article

Ann Hematol Oncol. 2015;2(6): 1048.

Immunoglobulin Heavy/Light Chain Quantification – Update on a New Biologic Marker in IgA Multiple Myeloma

Denimal D¹, Lemaire-Ewing S¹, Guy J², Maynadie M³, Bastie JN³, Lafon I³, Caillot D³ and Lakomy D¹*

¹Biochemistry Laboratory, University Hospital Dijon, France

²Haematology Laboratory, University Hospital Dijon, France

³Department of Clinical Haematology, University Hospital Dijon, France

*Corresponding author: Lakomy D, Biochemistry Laboratory, University Hospital Dijon, 2 rue Angelique Ducoudray, 21000 Dijon, France

Received: June 17, 2015; Accepted: July 30, 2015; Published: August 17, 2015


In IgA multiple myeloma (MM), monoclonal (M)-spike quantification by serum electrophoresis (SEP) encounters some limitations. Heavy/light chain (HLC) assay is a novel quantitative immunoassay allowing the measurement of IgAk and IgAλ concentrations. The aim of this study was to assess the performances of HLC assay to monitor disease, to detect progression and relapse and to evaluate residual disease in comparison with traditional routine tests.

We compared IgA HLC assay to SEP, immunofixation electrophoresis (IFE), total IgA concentration and bone marrow (BM) immunophenotyping in a routinely follow-up of 40 IgA MM patients (594 serums samples).

HLC assay correlated well with both total IgA and M-spike (when quantifiable) during the follow-up. IgAk/IgAλ ratio monitored progression disease more accurately than SPE. HLC ratio was slightly less sensitive than IFE in the early prediction of relapse. At the stage of complete response (CR), HLC ratio was in perfect agreement with IFE and BM immunophenotyping. Nevertheless, at the stage of near complete response (nCR), IFE and BM immunophenotyping were more sensitive in the assessment of residual disease.

In the current study, IgA HLC assay was found more performant than SPE in the monitoring of partial response and the disease progression but less sensitive than IFE to predict early relapse or to evaluate residual disease.

Keywords: Multiple myeloma; IgA; Heavy/light chain assay; Hevylite


MM: Multiple Myeloma; SPE: Serum Protein Electrophoresis; M: Monoclonal; IFE: Immunofixation Electrophoresis; IMWG: International Myeloma Working Group; Ig: Immunoglobulin; HLC: Heavy/Light Chain; BM: Bone Marrow; ASCT: Autologous Stem Cell Transplantation; nCR: Near Complete Response; CR: Complete Response; MFC: Multiparameter Flow Cytometry; NR: Normal Range


The evaluation of monoclonal (M) protein is a key point of the follow-up in multiple myeloma (MM). Indeed, international guidelines recommend serum protein electrophoresis (SPE) for quantification of monoclonal immunoglobulin (Ig) and immunofixation electrophoresis (IFE) to confirm complete response (CR) [1]. Uniform response criteria for MM are defined by the International Myeloma Working Group (IMWG) based on these well-established laboratory tests [2].

Nevertheless, the interpretation of these conventional laboratory tests can be difficult in IgA MM cases. In particular, an accurate measurement of M-spike by SPE is challenging, due to frequent comigration with other serum proteins in the β-region and/or to the broad electrophoretic migratory patterns [3-5]. IFE is more sensitive than SPE but as a qualitative technique it doesn’t allow quantification. As an alternative, nephelometric quantification of total IgA may be used, but without differentiating monoclonal and polyclonal Ig [2,4].

Since 2009, IgA heavy/light chain (HLC) assay is available providing separate quantification of IgAk and IgAλ and therefore the calculation of the IgAk/IgAλ ratio. This automated immunoassay is based on the recognition of the conformational epitopes at the junctions of the heavy chain and light chain constant regions of Ig [5].

The aim of this study was to evaluate whether the IgA HLC assay meets the criteria of the IMWG and whether it provides similar evaluation of response as the routinely used tests. In that purpose, we compared IgA HLC assay to SPE, IFE, total IgA and bone marrow (BM) analysis. We assessed the potential benefit of IgA HLC assay to monitor disease, to predict disease relapse and progression and to evaluate residual disease.

Materials and Methods

Forty patients presenting an IgA MM under different treatment regimens were routinely followed-up for several months (median 19 months) at the University Hospital of Dijon. Patients were followedup at different times: after induction chemotherapy, after autologous stem cell transplantation (ASCT), after the consolidation phase and during monitoring adapted to the disease evolution.

Sequential samples (594 sera) were kept frozen (<-20°C) until analysis and total IgA quantification, SPE, IFE, IgA HLC were assayed under routine clinical laboratory conditions. Twenty two BM samples were also collected.

IgAk and IgAλ quantification was realized using Hevylite™ reagents on a SPAplus™ analyser (The Binding Site, Birmingham, U.K.). SPE and IFE were performed on a Sebia Hydrasys™ analyser (Sebia, Evry, France). Total IgA were quantified with a dedicated reagent on the Siemens Dade Behring BNII™ nephelometer (Siemens Diagnostics). BM plasma cells were immunophenotyped by a Navios multiparameter flow cytometer (MFC) (Beckman Coulter). Reference values were those proposed by manufacturers.

Response to treatment was evaluated according to the IMWG criteria [2]. In addition, near complete response (nCR) class was used to define response to treatment characterized by negative SPE but positive IFE.

The correlation lines were obtained by linear regression and correlation coefficients were calculated using the Pearson’s test.

Results and Discussion

In MM, response to treatment is monitored by periodic assessment of M-Ig using several laboratory assays, each one with their advantages and their limitations. Our study evaluated IgA HLC assay in comparison with traditional biological markers in order to define which test performs the best at different stages of the disease during the follow-up.

IgA HLC assay and disease monitoring

IgA HLC results were compared with total IgA quantification and electrophoretic M-spike values during the monitoring of 40 IgA MM patients (26 IgAk and 14 IgAλ). The sum IgAk + IgAλ and total IgA concentrations were strongly correlated both in IgAk MM (335 samples, R²=0.962, Figure 1A) and in IgAλ MM (259 samples, R²=0.970, Figure 1B). By using the SPE method, the M-IgA migrated in β-region for 20 patients and in γ-region for the 20 other subjects. In 185 samples, M-spike values and HLC involved isotype concentrations were compared and were found well correlated (R²=0.938, Figure 1C). During the monitoring of all patients, the kinetic of concentrations was found to be similar between HLC involved isotype, M-spike and total IgA. A representative example in one patient with IgAk MM was shown in Figure 1D.