Abstract
Background aims. Enumeration of CD34+ cells in leukocyte-rich cell suspensions is important for clinical decision-making in stem cell transplantation. Single-platform flow cytometry assays offer the significant advantages of speed and reproducibility, and have therefore become the gold standard in stem cell enumeration. The clinical community has recently defined the need for stem cell enumeration kits that incorporate viability dyes. The purpose of this study was to evaluate a novel assay, BD Biosciences’ (BD) stem cell enumeration kit (SCE kit‡), in relation to Beckman Coulter's (BC) commercially available BC Stem-Kit™. Methods. Fresh/freeze-thawed samples from leukapheresis, bone marrow and cord blood, and fresh normal/mobilized blood, were analyzed with both assays (simultaneous detection of side/forward scatter and three fluorescence signals) on two flow cytometry platforms, BD FACSCanto II and BD FACSCalibur. Results. Results from both assays were highly congruent, with an overall r2 ≥ 0.99 (all specimen types included), a linear correlation across all CD34+ cell frequencies and concentrations, and an almost ideal steepness of the trend line. Conclusions. Both assays functioned reliably. Being based on single-platform International Society of Hematotherapy and Graft Engineering (ISHAGE) guidelines and similar staining methods, both assays essentially come to identical results. For most specimen types, the viability of CD34+ cells was equal to overall leukocyte viability. In summary, in the hands of an experienced technician, the BD™ SCE kit and the BC Stem-Kit are equivalent. The infrequent user might derive benefit from the fact that counting spheres are pre-pipetted into the Trucount tube for the SCE kit, making this assay less susceptible to pipetting inaccuracy.
‡The SCE kit is not for sale in the USA and is currently under investigation in the USA.
Acknowledgments
We acknowledge Katia Vancompernolle, Anna Lin, Lorlelei Lee-Haynes and Imelda Omana-Zapata from BD Biosciences for co-ordination of the study and review of the manuscript. The help of Nadine Sorg, Gabi Spamer, Christiane Vetter and Eva Wingenfeld, laboratory technicians in the stem cell laboratory of the German Red Cross Blood Service, Frankfurt, in providing and de-identifying specimens is gratefully acknowledged.
Declaration of interest: The performance evaluation study was sponsored by BD Biosciences. Generated data were used by the sponsor to support commercial distribution in Europe. The authors alone are responsible for the content of the paper and the analyzed data. None of the authors have a financial interest to declare.
Notes
‡The SCE kit is not for sale in the USA and is currently under investigation in the USA.