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. 2018 Jun 27;56(7):1169-1175.
doi: 10.1515/cclm-2017-0817.

Analytical Validation of the Hevylite Assays for M-protein Quantification

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Analytical Validation of the Hevylite Assays for M-protein Quantification

Joannes F M Jacobs et al. Clin Chem Lab Med. .

Abstract

Background: The heavy/light chain (HLC) immunoassay quantifies the different heavy chain/light chain combinations of each immunoglobulin (Ig) class. This makes the HLC assay suited to quantify monoclonal immunoglobulins (M-protein) and for monitoring of patients with monoclonal gammopathies. This method is particularly advantageous for those samples in which electrophoretic quantification of the M-protein is not possible.

Methods: In this study we tested the analytical performance of the HLC assay in 166 routine clinical samples and in 27 samples derived from the Dutch external quality assessment (EQA) for M-protein diagnostics (74 participating laboratories). Analytical accuracy was assessed by verification that the sum of the HLC-pairs equaled total Ig concentration. Sensitivity of the HLC assay was determined in a direct method comparison with immunofixation electrophoresis (IFE).

Results: Comparison of HLC data with routine Ig diagnostics in 27 EQA samples showed very good correlation for both the quantification of polyclonal and monoclonal IgG, IgA and IgM (Pearson correlations [r] were 0.94, 0.99 and 0.99, respectively; slopes were 0.94, 1.07 and 0.98, respectively). The overall concordance between IFE and the HLC ratio was high (93%) with a Cohen κ coefficient of 0.84. Discrepancies between both assays were mainly caused by the higher sensitivity of IFE to detect monoclonality.

Conclusions: We conclude that the HLC assay is an accurate method to quantify M-proteins that can improve monitoring of M-proteins in the beta fraction that cannot be quantified using electrophoretic techniques.

Keywords: M-protein; heavy/light chain immunoassay; immunofixation electrophoresis; monoclonal gammopathy; multiple myeloma; serum protein electrophoresis.

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