Use of Packed Red Blood Cell Mechanical Fragility to Indicate Transfusion Outcomes

The hypothesis for this study was that RBC mechanical fragility (MF) could be an aggregate in vitro property predictive of transfused RBC performance in vivo. Various MF values were obtained via MF profiling, based on several variations of testing parameters, using both a "legacy" approach (with a commercial, cam-based vertical bead mill and a spectrophotometer) and a more proprietary approach (with a custom-developed, electromagnetic horizontal bead mill combined with proprietary optics and analysis). A total of 52 transfusion events in 32 different patients recruited from the University of Michigan were included in this study. Results were assessed using mixed effects and linear regression models. RBC MF was shown to predict about 15% of transfusion-associated changes in patient hemoglobin concentration, but not of secondary hemolysis-associated metrics (serum hemoglobin, HAP, and LDH). This result was affected by several factors that were not fully accounted for, including variability in post-transfusion blood collection time and variability in each blood unit volumes. Inclusion of the number of units transfused showed the potential to improve predictive capability, thus highlighting the potential importance of underlying patient condition necessitating the second unit transfusion. Certain ways of applying the bead-induced mechanical stress showed MF results more suitable for predicting transfusion outcomes than others indicating potential significance of flow stress type for assessing storage-induced RBC membrane damage. That highlights an opportunity for improvement of the potential for use of MF metrics, through identification of optimal stress application parameters (possibly by further varying parameters used here, as well as others) for assessing contribution of storage-lesion-associated RBC damage on transfused RBC performance.