Evaluation of plasma cell sorting methods in multiple myeloma patients: flow cytometry versus magnetic beads

The prognosis of a plasma cell neoplasm (PCN) varies depending on the presence of genetic abnormalities. However, detecting sensitive genetic mutations poses challenges due to the heterogeneous nature of the cell population in bone marrow aspiration. The established gold standard for cell sorting is fluorescence-activated cell sorting (FACS), which is associated with lengthy processing times, substantial cell quantities, and expensive equipment. Magnetic-activated cell sorting (MACS) can be performed without the need for FACS equipment and allows for rapid sorting of many cells, making it a practical alternative. Our objective is to conduct a comparative analysis of these two sorting techniques to assess whether MACS can viably replace FACS in clinical applications.

Plasma cell purity, fluorescence in situ hybridization (FISH), and next-generation sequencing analyses were performed on FACS- and MACS-sorted bone marrow samples from 31 PCN patients.

The MACS-sorted samples yielded a higher percentage of plasma cells than FACS-sorted samples under microscopy (p = 0.0156) and flow cytometry (p = 0.0313). FISH performed by two methods in 10 samples showed the same results, and the proportion of abnormal cells was significantly higher in MACS than in FACS (p = 0.001). Wilcoxon matched-pairs signed rank test analysis showed that the median of differences of variant allele frequency (VAF) of two methods (VAF of MACS minus VAF of FACS) in the DNMT3A, TET2, and ASXL1 (DTA) group was - 0.006555 (p = 0.0020), while that in the non-DTA group was 0.002805 (p = 0.0019). Ten copy number variants (CNVs) were found in both FACS- and MACS-sorted samples, eight were identified only in MACS-sorted samples, and one was detected only in FACS-sorted samples.

Our study demonstrates that MACS is a viable alternative for plasma cell sorting in bone marrow samples of patients with PCN.