Assessment of haematopoietic progenitor cell counting with the Sysmex® XN-1000 to guide timing of apheresis of peripheral blood stem cells

Abstract

Background. Successful peripheral blood stem cell (PBSC) collection depends on optimal timing of apheresis, as usually determined by flow cytometry CD34-positive (⁺) cell count in peripheral blood (PB). Since this method is costly and labour-intensive, we evaluated the use of the Hematopoietic Progenitor Cell count programme on a Sysmex^® XN haematologic analyser (XN-HPC) as a rapid and inexpensive alternative for predicting CD34⁺ cell count in PB samples.
Materials and methods. Haematopoietic progenitor cell and CD34⁺ cell counts were compared using 273 PB samples collected from 78 healthy donors and 72 patients who underwent PBSC transplantation. We assessed the effectiveness of the XN-HPC in safely predicting pre-harvest CD34⁺ counts. The most efficient cut-off values of XN-HPC were identified. We also evaluated the imprecision (coefficient of variation, CV) and functional sensitivity.
Results. Imprecision of the XN-HPC count was <6.3% on daily measurement of three levels of quality control material. Functional sensitivity was 8.9×10⁶/L. A cut-off value of ≥62×10⁶/L XN-HPC for multiple myeloma (MM) patients and ≥30×10⁶/L for all other subjects had both 100% specificity and 100% positive predictive value for identifying samples with CD34⁺ cells ≥20×10⁶/L. An XN-HPC threshold of <13×10⁶/L identified pre-harvest CD34⁺ cell count <10×10⁶/L with 100% sensitivity and 100% negative predictive value.
Discussion. The XN-HPC is a fast, easy and inexpensive test that can safely improve apheresis workflow thus possibly replacing other more expensive CD34 counts currently performed and promoting optimal timing of PBSC collection.