IGA MULTIPLE MYELOMA ASSESMENT WITH HEVYLITE ASSAY

Abstract

Introduction: A key element on Multiple Myeloma (MM) evaluation is the quantification of monoclonal proteins. Current techniques include Serum Protein Electrophoresis (SPE), Immunofixation (IFE) and Free Light Chain Assay (FLC, Freelite). All assays are clinically relevant but have some limitations. Especially for IgA MM patients, SPE could be inaccurate, insensitive due to comigration, lack of sensitivity below 10 g/L and has subjective interpretation, among other limitations. IFE have greater sensitivity but is only qualitative. Hevylite, an immunoassay based on polyclonal antibodies that measure IgA-κ and IgA-λ independently, quantifies these proteins while identifying clonality through its ratio (IgA-κ/IgA-λ, HLCr) and gives additional clinical information, especially for difficult IgA MM patients serum samples. Aim: To test Hevylite assay and to evaluate its lab and clinically relevance for IgA MM patients. Material and methods: 44 IgA MM patients were evaluated in this study. All were received at protein lab for MM query between Feb-May 2023. Patients were selected according to: CZE: Monoclonal component or distortion of alfa-2 or beta fraction. IFE: Monoclonal component IgA-Kappa or IgA-Lambda isotype. Measurement of IgA-κ and IgA-λ were performed using Hevylite™assay (The Binding Site) according to manufacture recommendations in a turbidimetry (Optilite, The Binding Site). CZE with Capillarys 3 (Sebia) and IFE with Hydrasys 2 (Sebia). Patients were classified: IgA-κ MM, IgA-λ MM and non-MM. Patient's evaluation was performed following IMWG recommendations. Results: Serum level of monoclonal protein and discrimination between monoclonal and polyclonal components are crucial in the follow up of MM patients. All IgA MM patients in the study showed an abnormal HLCr IgAκ/IgAλ indicating clonality. IgAκ or IgAλ levels were abnormally high when the isotype was monoclonal. HLCr allowed a better discrimination between groups and an accurate identification of myeloma patients at diagnosis. Concordance grade (0,927) between HLCr and IFE qualitative results were analyzed with Cohen k coefficient. Hevylite allowed accurate identification and quantification of M protein in 10 IgA MM patients that couldn't be resolved by CZE. Case#1. IgAκ: 3,849 g/L, IgAλ: 0,032 g/L. HLCr: 120,28. CZE β1-2 fraction alteration without signs of monoclonal component. Hevylite solved this patient's evaluation. Conclusions: The performance of Hevylite assay as a biomarker in IgA monoclonal gammopathies allow us: To use a full automated lab assay, easy to run in daily routine. To better discriminate monoclonal components that co-migrates in CZE, especially IgA monoclonal proteins. To increase the sensitivity to detect monoclonal protein compared to CZE, given a quantitative and reproducible results of both monoclonal isotype (involved) and non-monoclonal isotype (uninvolved) in the patient serum sample. To use as a clinical tool to overcome traditional methods'limitations on monoclonal gammopathies detections and follow up. Overall, our results showed that Hevylite could be a useful clinical tool, with increased sensitivity compared with electrophoretic methods and that can provide additional clinical information overcoming electrophoresis limitations and allowing more MM serum samples to be accurate evaluated and, and the end, to better manage IgA MM patients.