The method for enumeration of hematopoietic stem/progenitor cells (HPC) described in the European Pharmacopoeia is based on flow cytometry with sequential gating according to the ISHAGE guidelines. The high precision and accuracy of this method have been consistently demonstrated. We identify a space for point-of-care (POC) technology for enumeration of circulating HPCs to determine apheresis readiness of mobilized patients or enumeration of HPC dose during apheresis.

We posit that these uses could potentially be assisted by the non-compendial cell counter ADAMII (NanoEntek, Seoul, Korea). ADAMII is a compact table-top fluorescent imager facilitating acquisition of 75 individual fields of vision with four image sets each (bright field and fluorescence channels for CD34, CD45 and a viability dye) which are digitally overlaid to detect marker co-expression. ADAMII thus provides direct assessment of target cell concentration without the need for counting beads. We assessed the performance of ADAMII for HPC enumeration in 42 random mobilized blood (MPB) and 39 mobilized apheresis (HPC-A) samples relative to conventional compendial single-platform flow cytometry (SCE, Becton-Dickinson, Heidelberg, Germany).

Viable HPC enumeration was mostly congruent between the methods for MPB (range 36-380/µL) and HPC-A (range: 331-8695/µL), with R²=0.9046, slope 0.9447 for MPB and R²=0.9724, slope 1.0758 for HPC-A, although differences between the methods exceeding 10% were noted in almost half, exceeding 20% in a quarter of the samples. A quite good correlation was equally observed for viable leukocyte count (R²=0.9154 and R²=0.8295 for MPB and HPC-A, respectively) and HPC frequency (R²=0.9347 and R²=0.9755 for MPB and HPC-A, respectively).

Because MPB samples in the relevant decision range for patient apheresis readiness were insufficiently represented, analysis of a second MPB cohort with low HPC concentration samples (0-30/µL) was initiated and will be presented at the DGTI meeting. Our preliminary data indicate suitability of ADAMII as POC analysis tool to determine apheresis readiness of patients and HPC content in apheresis products which remains, however, to be corroborated in low-mobilization samples.

JL and CYP are employees of NanoEntekt, manufacturers of the device evaluated here. The other authors have no declarations with respect to this work.