Comparison between single‐ and dual‐platform flow cytometry for CD34 + stem cell enumeration in a pediatric population

Background CD34+ hematopoietic progenitor cells (HPCs) enumeration is essential for stem cell collection adequacy. Both single (flow cytometer only) and dual‐platform (flow cytometer and hematology analyzer calculation) methodologies are used, but their comparative accuracy and implications for pediatric patients remain unclear. Study Design and Methods We conducted a retrospective review of 131 autologous apheresis (HPC(A)) collections from 120 pediatric patients at a single institution (2017–2023). Assessment included differences between the two platforms as absolute and percent differences and agreement, systematic bias and association between hematology analyzers and patient characteristics with CD34+ percent differences. The impact on whether additional days of collection would be needed was assessed by comparing CD34+ dose thresholds. Results Absolute CD34+ counts were highly correlated but exhibited systematic bias. Single platform absolute CD34+ were significantly higher, especially in HPC(A). Percent differences averaged 6.3% in peripheral blood and 15.9% in HPC(A). Enumeration discrepancies varied by hematology analyzer and patient characteristics. Age, weight, and type of disease affected enumeration consistency between platforms. In 3 of 10 patients, the enumeration method potentially impacted the number of collection procedures, as the minimum CD34+ dose thresholds were met using single platform but not with dual. Discussion Enumeration methods impact CD34+ counts and may alter clinical decisions regarding collection adequacy and need for additional days of collection. One must understand the variability in each testing methodology as it may translate to a clinically significant outcome. Method‐specific adjustments or standardization protocols may be needed to ensure accurate interpretation in pediatric care.