Sanne de Bruin

167 Storage of RBCs in PAGGGM improves metabolism after transfusion but has no effect on PTR expected fraction of bioRBCs and comparison with the measured fraction of bioRBCs. Another limitation is that we infused 25 ml per RBC concentrate. It is unclear how fast the spleen is saturated by RBCs and therefore how these results can be extrapolated to a standard RBC concentrate that contains 300 ml. Our study is also biased towards testing metabolism of the cells that could be recovered upon transfusion, making the cells to be more likely to be metabolically divergent (i.e., the ones carrying the most damage upon storage) less likely to be recovered from the bloodstream of autologous recipients. In this view, it is worth noting that prior studies on the metabolic impact of autologous transfusion of end of storage units indeed reported significant alteration of plasma and RBC metabolism in the recipient 43 , suggesting that any difference in the present study may at least in part, go undetected due to the limited volume transfused (25 ml vs half a unit in prior studies). Yet, the present study shows a proof of feasibility with respect to the capacity to recover in vivo biotinylated RBCs for omics analyses upon transfusion. And finally, due to the small sample size and the exploratory character of this study no Bonferroni correction was applied in the metabolomics analysis. This may have resulted in a type 1 error. However, we assessed multiple metabolites in several pre-specified pathways, and as the majority of these metabolite were affected, we be- lieve that the chance of a type 1 error is limited. In conclusion, despite a better metabolic profile of PAGGGM RBCs, PAGGGM storage did not lead to a higher PTR. Furthermore, the metabolic storage lesion was corrected within a day after transfusion in cells that did not undergo intra- or extra-vascular hae- molysis and still circulated 24h after transfusion. Finally, 35 days of storage resulted in a lower PTR compared to 2 days of storage. 6