B-181 Multi-centre Analytical Performance Evaluation of the EXENTâ Solution for Identification and Quantitation of Monoclonal Immunoglobulins

Abstract

Abstract Background Current routine methodologies for monoclonal immunoglobulin measurements may not be sufficiently sensitive to reflect the depth of response seen in patients since the introduction of novel therapies; mass spectrometry may offer a valuable, sensitive alternative approach. Here we describe the preliminary analytical performance characteristics of the EXENT® solution (in development by The Binding Site, part of Thermo Fisher scientific) that combines specific immunoprecipitation steps and mass spectrometry for the identification and quantification of IgG, IgA and IgM intact monoclonal immunoglobulins. Each intact monoclonal immunoglobulin clone can be tracked using its unique m/z value. Methods The Lower Limit of Measuring Interval (LLMI) was established for each immunoglobulin type following EP17-A2:2012. Linearity studies were performed according to CLSI EP06-A2:2020 using high and low pools of IgG, IgA, and IgM monoclonal samples and with additional linearity testing below 1 g/L for each specificity to more effectively demonstrate low-end linearity. Within run, between run, between analyzer, between lot and total precision for M protein concentrations and for molecular mass (m/z) of the monoclonal peaks were assessed according to CLSI EP5-A3-2014. Interference was tested following ED3:2018 using 20 potential interferents against 7 samples including high and low IgG, IgA and IgM monoclonal samples. Results The initial indication of the EXENT solution performance, in development, are set out below. Results suggest an analytical sensitivity of the assays around 15 mg/L at the LLMI for all specificities. Linearity over a range of 0.014–88.9 g/L for IgG, 0.011–68.4 g/L for IgA, and 0.11–74.2 g/L for IgM. Coefficients of variation (CVs) for M protein concentrations in precision studies were <15% for all specificities and samples. Mass/charge values were within ±1.1 to ±1.5 m/z in total precision studies, and within ±2.7 to ±3.9 m/z in between lot precision studies, respectively, for M proteins with an m/z value ranging from 11 360.6 to 11 698.5 m/z. No significant interference effects were observed when testing the 20 interferents including intralipid (20 g/L), triglyceride (15 g/L), bilirubin (400 mg/L), rheumatoid factor (200 IU/mL) and haemoglobin (10 g/L). Conclusion The new EXENT solution demonstrates the potential for a wide measuring interval and the ability to detect M proteins with very low concentration. Also, it could provide stable and reproducible performance for the detection and typing of monoclonal immunoglobulins.