Donor citrate reactions influence the phenotype of apheresis platelets following storage

Platelet collection and processing methods, as well as donor attributes, can influence platelet function and quality during ex vivo storage. In this study, activation and procoagulant responses in platelets collected from donors experiencing a citrate reaction (CR) were investigated.

Apheresis platelet components (n = 54) were stored in 100% autologous plasma and tested on days 1 and 5 post-collection. Platelet components were categorized into two groups according to whether the donor had experienced a CR during donation (n = 10; non-CR group, n = 44). Platelet aggregation was initiated with collagen and thrombin. Platelet phenotype was characterized by flow cytometry. Fibrinogen binding was assessed following collagen + thrombin stimulation (COATed platelets), and procoagulant activity was assessed using a procoagulant phospholipid assay (PPL). Platelet microparticle (PMP) subsets were enumerated by flow cytometry.

Basal von Willebrand factor (VWF) binding was higher in the CR donations when compared with the non-CR group. Collagen aggregation was significantly higher in platelets from CR donations, in contrast to aggregation induced by thrombin. The proportion of phosphatidylserine (PS) positive PMP and PPL clotting time were higher in the CR group, in contrast to the number of basal PS⁺ platelets and COATed platelets following stimulation.

Platelets donated by donors who experienced a CR during donation had higher platelet activation response and possibly a more procoagulant PMP phenotype, suggesting that this donor reaction might lead to increased platelet activation.