Is volume the only factor that impacts cord blood processing efficiency?

We fi nd the article by Meyer-Monard et al. (1) in the February 2012 issue of Cytotherapy interesting, especially with regard to the implications for larger cord blood collections that some banks routinely split prior to processing. We agree with the authors that optimizing processing effi ciency is critical to ensure the highest recovery of stem cells possible. However, have the authors considered that, in addition to collection volume, the extent to which a cord blood unit is diluted by citrate phosphate dextrose (CPD) affects processing effi ciency? In our opinion, careful consideration of the impact of anticoagulant on cord blood has been vastly underappreciated. The adoption of CPD concentrate as formulated for peripheral blood collections by cord blood banking may have unintended consequences on unit quality because of the variable range in collection volumes. Our group and others have postulated that there are dilution-associated effects for cord blood units collected in citrate-based anticoagulants that may adversely affect processing effi ciency and unit quality. Prior to converting to a fully automated system, we reported that CPD affects cell recovery of Ficoll processing. Our data show an increase in postprocessing cell yield for larger volume units ( 70 mL) collected in CPD compared with medium and small units (40 – 70 and 39 mL) (2). Increasing the concentration of CPD in peripheral whole blood collections has been reported to increase mean corpuscular volume of red blood cells, compromising cell stratifi cation and reducing cell recovery in the automated AutoXpress TM processing platform (3). Pope et al. (4) reported that for cord blood units collected in CPD and processed with the automated Optipress II platform, cell viability was signifi cantly affected by the collection volume and time to freezing. Based on their observations, those authors postulated that at low collection volumes there is a greater dilution of blood by a standard volume of anticoagulant and that a high ratio of anticoagulant to blood may be detrimental to cell viability. We have also reported a signifi cant loss of cell viability of cord blood units collected in CPD and held at room temperature for 24 – 48 h (5). Taken together, these studies suggest that exposure to CPD at a larger than intended CPD to blood ratio may decrease cord blood cell viability and adversely impact processing effi ciency across multiple volume reduction platforms. We suggest that Meyer-Monard et al. (1) test their hypothesis on large-volume units that are split prior to processing, thereby maintaining the anticoagulant to blood ratio. Our hypothesis is that because there is less of a dilution effect the results might be more consistent with previous studies reporting a linear correlation between blood volume and processing effi ciency (6). We believe there is suffi cient evidence regarding adverse effects associated with collecting cord blood in CPD for this to be a cause for concern, and that these effects may be particularly disadvantageous for smaller volume collections. The anticoagulant used in cord blood banking therefore represents yet another variable that deserves the same intense scrutiny that has been given to processing and cryopreservation in the effort to maximize cord blood unit quality. Cytotherapy, 2012; 14: 1022–1023