Limited Utility of Flow Cytometry Immunophenotyping for Assessment of Plasma Cells in Hematopoietic Progenitor Cell Apheresis Product from Patients with Multiple Myeloma

Abstract Aim Flow cytometric immunophenotyping (FCI) is routinely performed in our laboratory to assess the clonality of plasma cells in hematopoietic progenitor cell apheresis (HPC-A) products as part of the quality control for multiple myeloma patients undergoing autologous stem cell transplantation. The purpose of this project is to investigate whether FCI is indicated for HPC-A when FCI is also performed on a bone marrow biopsy sample obtained before or after HPC-A collection. Materials and Methods The FCI results of HPC-A samples were retrieved from the laboratory database and analyzed. Relevant FCI results of the corresponding bone marrow biopsy samples were also retrieved and analyzed. All FCI was performed using BD FACSCalibur/FACSCanto with a four-color antibody panel, and the listmode data were analyzed by BD FACSDiva. Results FCI was performed on a total of 1,621 HPC-A samples in our laboratory from 02/01/2012 to 02/02/2018. A total of 58 HPC-A samples were positive for a monoclonal plasma cell population (3.8% of the total sample). Among those positive samples, 55 had bone marrow biopsy done before or after HPC-A collection: 38 within a month, 8 between 1 and 2 months, and 9 between 3 and 6 months. Fifty-four of 55 bone marrow samples were positive for a monoclonal plasma cell population by FCI. Conclusion The utility of FCI in the quality assessment of HPC-A products from patients with multiple myeloma is a very limited when FCI is performed on a bone marrow biopsy obtained within 6 months of HPC-A collection.