Comparison of minimal residual disease detection in multiple myeloma by SRL 8-color single-tube and EuroFlow 8-color 2-tube multiparameter flow cytometry.

We sought to determine the efficacy of a new, inexpensive, single-tube 8-color multiparameter flow cytometry (MFC) method (SRL-Flow), which is based on the EuroFlow next-generation flow (NGF) (tube 2 only), to assess minimal residual disease (MRD)-negative status. MRD-negative status is considered a treatment milestone in multiple myeloma (MM). We used 45 bone marrow samples from patients with MM, including 11 cases treated with anti-CD38 monoclonal antibody. The SRL-Flow sample preparation protocol was identical to that of EuroFlow-NGF. The antibody panel for SRL-Flow was as follows: CD138V450/CD27V500/CD38ME (multiepitope)FITC/CD56PE/CD45PerCP-Cy5.5/CD19PE-Cy7/cytoplasmic (Cy) immunoglobulin (Ig) κAPC/CyIgλAPC-H7. To identify abnormal plasma cells (aPCs) of patients with MM who received anti-CD38 monoclonal antibody, we used a panel of anti-CD45 and anti-CD138 antibodies (Abs) rather than a panel of anti-CD45 and anti-CD38 Abs. We comparatively analyzed the total nucleated cell numbers, total PC levels, and MRD levels between the SRL-Flow and EuroFlow-NGF. High correlations (r > 0.9) in total PC and MRD levels were noted among SRL-Flow, original EuroFlow-NGF (2 tubes), and EuroFlow-NGF (tube 2 only), suggesting that SRL-Flow is an inexpensive (< $200 USD/sample as of January of 2019) alternative to EuroFlow-NGF (< $350 USD/sample) for assessing MRD in MM.