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

Method comparison between hematopoietic progenitor cell and CD34+ cell counts in hematopoietic stem cell collection

BACKGROUND

The reference method for hematopoietic stem cell enumeration is flow cytometric CD34+ cell analysis. We evaluated using the hematopoietic progenitor cell (HPC) count on the Sysmex hematology analyzer to safely replace some flow cytometric measurements performed in peripheral blood samples to guide apheresis timing.

STUDY DESIGN AND METHODS

We compared HPC and CD34+ cell counts in 133 preharvest peripheral blood samples and 124 apheresis products.

RESULTS

Pre-apheresis HPC counts ≥24 × 106/L in healthy donors and ≥36 × 106/L in lymphoma patients predicted adequate mobilization with 100% specificity and positive predictive value, saving 79% and 63% of flow cytometry analyses, respectively. Due to a positive bias (mean bias 50.26; 95% CI 36.24-64.29), a higher threshold was needed in multiple myeloma patients (HPC≥ $$ \ge $$ 132 × 106/L), saving only 24% of flow cytometry analyses.

CONCLUSION

When the HPC count is above the corresponding threshold, apheresis could be safely initiated without waiting for the flow cytometry result, thereby reducing time-to-decision. Lower HPC values, however, require confirmation by flow cytometry.

Widely applicable, extended flow cytometric stem cell enumeration panel for quality control of advanced cellular products

The most widely used quality control assay for CD34 + hematopoietic stem cell product characterization is the protocol established by the International Society of Hematotherapy and Graft Engineering (ISHAGE). While this protocol is still the gold standard for stem cell enumeration and viability assessment, it does not include T cell enumeration, which is nowadays mandatory for assaying standard allogeneic grafts and various advanced therapy medicinal products (ATMPs). In accordance, we have developed and extensively validated a new approach for a more comprehensive characterization of hematopoietic cellular products using a pre-formulated dried antibody format panel. In addition to the counting beads, the typical markers CD45 fluorescein isothiocyanate (FITC) and CD34 phycoerythrin (PE), as well as the viability dye 7-amino actinomycin D (7-AAD), our novel pre-formulated panel also contains CD3 Pacific Blue (PB) and CD19 allophycocyanin (APC) in the same tube, thereby allowing a combined calculation of leucocytes, stem cells, T and B cells. Showing high linearity, sensitivity and accuracy, our approach is easy to implement and enables a more in-depth characterization of the cellular product under release testing conditions. In addition, the dried pre-formulated antibody approach increases assay reliability compared to the standard antibody panel.