Predicting Successful Hematopoietic Stem Cell Collection in Healthy Allogeneic Donors

Abstract

<b><i>Introduction:</i></b> Collection of peripheral blood stem cells (PBSCs) from healthy donors is a well-established process. We aimed to identify factors predictive of successful CD34+ PBSC collection and established a formula capable of predicting CD34+ cell yield. <b><i>Methods:</i></b> We retrospectively evaluated 588 healthy adult donors (median age 29 years, range 18–69 years) at our institution from 2017 to 2022. The predicted minimal number of CD34+ cells was calculated as follows: (peripheral CD34+ cells/µL × adjusted collection efficiency of 30%) × total liters processed. This formula was further modified according to donor and recipient body weight (BW). <b><i>Results:</i></b> Median total collection was 8.0 × 10⁶ CD34+ cells/kg BW (range 1.0–47.1 × 10⁶ cells/kg BW) with 522 donors (89%) collecting ≥5.0 × 10⁶ cells/kg of recipient BW. A second leukapheresis (LP) was performed in 49 donors. Need for two LPs was more common in female donors (OR 6.68, 95% CI, 2.62–17.05; <i>p</i> &lt; 0.001), donors with higher age (OR for 10 years difference 1.53, 95% CI, 1.15–2.03, <i>p</i> = 0.003), donors with WBC count &lt;30 × 10⁹/L after 5 days of granulocyte-colony stimulating factor (G-CSF) stimulation (OR, 4.33; 95% CI, 1.59–11.83; <i>p</i> = 0.004), and a donor/recipient weight ratio &lt;1 (OR 6.21, 95% CI, 2.69–14.34; <i>p</i> &lt; 0.001). Predictive factors for optimal LP (i.e., ≥5.0 × 10⁶ CD34+ cells/kg of recipient BW) were peripheral blood (PB) CD34+ cell count &gt;50/µL (OR 12.82, range 6.34–25.92, <i>p</i> &lt; 0.001), male donor (OR 2.77, range 1.06–7.23, <i>p</i> = 0.04), and a donor/recipient weight ratio &gt;1 (OR 3.12, range 1.57–6.24, <i>p</i> = 0.001). WBC, platelets, hemoglobin, and age had no significant predictive value. Predicted versus observed number of CD34+ cells/kg BW collected demonstrated a very strong linear correlation (<i>r</i> = 0.925, 95% CI, 0.912–0.936, <i>p</i> &lt; 0.0001). <b><i>Conclusions:</i></b> Of the routinely monitored indicators in PBSC donors, CD34+ cell count in PB is the most important factor in predicting G-CSF-induced PBSC yields. Higher age, female sex, WBC &lt;30 × 10⁹/L, and a donor/recipient weight ratio &lt;1 are useful indicators for identifying suboptimal mobilizers. The modified formula has shown successful and consistent performance in the prediction of key outcome measures including the minimum CD34+ cell collection, determination of the required length of apheresis, and whether a second day of PBSC collection was necessary to achieve the respective collection goal.