Bone Marrow Transplantation https://doi.org/10.1038/s41409-018-0353-8 ARTICLE Peripheral blood progenitor cell collection in pediatric patients optimized by high pre-apheresis count of circulating CD34+ cells and high blood flow Axel Karow 1 ● Anna Wilhelm 1 ● Roland A. Ammann 1 ● Gabriela M. Baerlocher 2 ● Thomas Pabst 3 ● Behrouz Mansouri Taleghani 2 ● Jochen Roessler 1 ● Kurt Leibundgut 1 Received: 9 May 2018 / Revised: 5 September 2018 / Accepted: 20 September 2018 © Springer Nature Limited 2018 Abstract Collection of peripheral blood progenitor cells by leukapheresis is the preferred method to obtain grafts for autologous transplantation. Optimizing this procedure is important to warrant sufficient cell yield and reduce associated risks. To obtain sufficient to optimal yields of ≥ 2 to ≥ 5 × 10 6 CD34+ cells/kg body weight with a single leukapheresis procedure, success rates between 83 and 92% have been reported in children. In this retrospective study, we describe an improved protocol for autologous stem cell collection with an extraordinarily high success rate applied in 122 consecutive pediatric patients treated at the University Hospital Bern between 2004 and 2017. By comparing our data with previous studies, we identify two main optimizing factors: higher pre-apheresis CD34+ cell counts with a median of 130/μl and higher blood flow rates of 42–100 ml/min. Consequently, blood volumes processed were increased, duration of leukapheresis was shorter and CD34+ cell yields with a median of 19.0 × 10 6 /kg body weight were higher than previously described. Safety in our study was comparable to previous studies. Based on our data, we present an innovative algorithm for determination of the necessary blood volume and time of pediatric leukapheresis procedure. Introduction For more than two decades, peripheral blood progenitor cells (PBPCs) have substituted bone marrow as the source of stem cells for autologous transplantation in both adults and children. A number of studies have been published with the aim to optimize different aspects of PBPC collection in pediatric patients usually focusing on children below 20 kg and 25 kg body weight (BW). These investigations mainly addressed PBPC mobilization, technical aspects of leuka- pheresis, and prediction of cell yield [1–3]. Until today, different mobilization schemes based on granulocyte–colony-stimulating factor (G-CSF) alone or in combination with granulocyte macrophage–colony-stimu- lating factor (GM-CSF) or chemotherapy followed by G-CSF alone or in combination with GM-CSF are used in different centers [4–13]. Additional rescue administration of plerixafor is restricted to patients with mobilization failure [14]. Technical approaches of leukapheresis being of parti- cular importance in small children also varied between different centers [1, 7–9]. Large-volume leukapheresis defined as processing at least three times the total blood volume (BV) of the donor and shown to be safe and efficacious was applied in the majority of pediatric studies [1, 8, 9, 15, 16]. The most predictive parameter for cell yield is the pre-apheresis count of circulating CD34+ cells [7, 9, 13, 17, 18]. Depending on the target CD34+ cell yield, considered sufficient when ≥ 2 × 10 6 CD34+ cells per kg BW per * Axel Karow axel.karow@insel.ch 1 Division of Pediatric Hematology/Oncology, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland 2 Department of Hematology, University Hospital/Inselspital Bern and University of Bern, Bern, Switzerland 3 Department of Medical Oncology, University Hospital/Inselspital Bern and University of Bern, Bern, Switzerland Electronic supplementary material The online version of this article (https://doi.org/10.1038/s41409-018-0353-8) contains supplementary material, which is available to authorized users. 1234567890();,: 1234567890();,: