P02 Inherent Variation in Donor Platelet Reactivity Contributes to the Quality of Apheresis Platelets

Abstract

Introduction Provision of platelets is a major commitment for Blood Services. Iterative cycles of improvements in platelet procurement and storage have lead to a better quality of concentrates, but even the latest generation of apheresis machines may produce activated platelets. Less attention has been paid in determining the contribution of an individual donor's inherent platelet reactivity on the activation state of apheresis platelets. We investigated this donor related variable using a panel of donors from the BLOODOMICS project whose platelet responses to activation through the ADP and collagen pathways were known to represent the widest range of the normal responses. For the current study three groups of donors with responses that were characterised as high (n = 16), low (n = 15) or in the mid‐range (n = 16), were recalled and the activation state of their circulating platelets and donated apheresis platelets were measured.Method To assess the activation state of platelets in the circulation, prior to donation samples were taken using a 21G butterfly needle, without a tourniquet. Aliquots of platelets from the apheresis donation were taken immediately at the end of the procedure. The level of platelet‐bound fibrinogen, a sensitive marker for early‐stage activation was measured using a whole‐blood flow cytometric assay.Results Prior to donation resting bound fibrinogen levels in all subjects ranged from 1.6–11.1% (mean 3.6%), and there was a significant association between this index of baseline platelet activation and the donor's responder status (P = 0.009). The percentage of platelets with bound fibrinogen in the apheresis concentrates ranged from 0.6–84.3% (mean 14.7%) and were generally higher than resting levels. Increased apheresis‐induced activation was associated with the responder status of the donor (P = 0.005). In particular, the 4 platelet concentrates with the highest levels of bound fibrinogen (>50%) were all from high responder donors.Conclusion Overall it is not solely the process of donation that affects platelet quality. Platelets that show higher responses to agonists are particularly susceptible to activation during collection by apheresis. We postulate that the responses to agonists are largely genetically controlled, and are attempting to identify the relationship between variation in platelet‐gene sequence and platelet function.