Establishment of Immunoglobulin Heavy (IGH) Chain Clonality Testing by Next-Generation Sequencing for Routine Characterization of B-Cell and Plasma Cell Neoplasms

Immunoglobulin heavy chain (IGH) clonality testing by next-generation sequencing (NGS) offers unique advantages over current low-throughput methods in the assessment of B-cell lineage neoplasms. Clinical use remains limited because assays are not standardized and validation/implementation guidelines are not yet developed. Herein, we describe our clinical validation and implementation of NGS IGH clonality testing and summarize our experience based on extensive routine use. NGS-based clonality testing targeting IGH FR1, FR2, FR3, and the conserved leader sequence upstream of FR1 was validated using commercially available kits. Data were analyzed by commercial and in-house-developed bioinformatics pipelines. Performance characteristics were evaluated directly comparing with capillary electrophoresis (CE) assays (BIOMED-2 primers). Assays were monitored after implementation (>1.5 years), concurrently testing by CE methods. A total of 1189 clinical samples were studied (94 validation, 1095 postimplementation). NGS showed superior performance compared with CE assays. For initial assessment, clonality detection rate was >97% for all malignancy types. Concordance with CE was 96%; discordances were related to higher sensitivity/resolution of NGS and improved detection in cases with high somatic hypermutation. Routine NGS clonality assessment is feasible and superior to existing assays, enabling accurate and specific index clone assessment and future tracking of all rearrangements in a patient sample. Successful implementation requires new standardization, validation, and implementation processes, which should be performed as a multicenter and multidisciplinary collaboration.