Validation of a formula predictive of peripheral blood stem cell yield and successful collection in healthy allogeneic donors

An efficient mobilization and collection of peripheral blood stem cells (PBSCs) are crucial to optimize engraftment in the recipient. We aim to validate a formula that predicted CD34+ cell yield and to describe variables that correlated with high yield mobilization and collection in healthy donors. We retrospectively analyzed clinical and laboratory data from healthy donors who underwent PBSC collection from 2006 to 2015. The predicted number of collected cells was calculated using the following formula: Total number of CD34+ (cells × 106/kg) yield = [(peripheral CD34+ cells/μL) × (0.43)/recipient body weight (kg)] × total liters processed. We evaluated 338 collections from 307 allogeneic PBSC donors. The predicted versus the observed number of CD34+ cells/kg collected yielded an r-value of 0.775 (0.726–0.816; p < 0.0001). Overall, 55.7% donors had an acceptable mobilization level. Donors with a body weight <67 kg were less likely to yield a satisfactory CD34+ cell count (OR = 0.44; 95% CI 0.24–0.81), while a white blood cell (WBC) count >40 × 109/L (OR = 3.69; 2.11–6.46) and platelet count ≥200 × 109/L (OR = 2.09; 1.26–3.47) on the day of collection predicted a good level of mobilization. Predictors of a CD34+ cell yield/kg of ≥4 × 106 with only one apheresis session were: circulating CD34+ cells/μL >40 (OR = 16; 6.94–36.93), hemoglobin ≥14 g/dL (OR = 3.40; 1.53–7.57), WBC >40 × 109/L (OR = 4.61; 2.10–10.10) on the first collection day, and a positive delta weight between donor and recipient (OR = 3.10; 1.36–7.06). The formula for predicting CD34+ cell yield is accurate and suggests the optimal length of time for successful leukapheresis. Validation of the predictors of successful mobilization will help to further refine PBSC leukapheresis procedures.