Distinct hemostatic and immune profiles of cold-stored apheresis platelets compared to leukoreduced whole blood

Cold-stored platelets (CSPs) are used in active bleeding due to their extended shelf life and preserved hemostatic function. Although both CSPs and cold-stored whole blood (CS-WB) are used clinically, the comparative effects of cold storage on their hemostatic and immunological properties remain partially understood. This study evaluated longitudinal changes in platelet function and immune markers stored at 4°C for 21 days.

Eight healthy donors each provided an apheresis platelet (AP) unit in plasma and a whole blood (WB) unit, leukoreduced using a platelet-sparing filter. Baseline samples were collected prior to cold-storage and on days 2, 7, 14, and 21 of cold-storage. Hemostatic, metabolic, and immunological parameters were assessed by aggregometry, clot retraction assays, and flow cytometry.

At baseline, CD62P, Annexin V binding, CD47 expression, and aggregation amplitude did not differ significantly between products. CD154 was higher in apheresis platelets. Over 21-day cold storage, CS-WB exhibited a more pronounced decline in aggregation and metabolic functions. Expression of activation markers (CD62P, Annexin V) increased in both products, with a stronger rise in CS-WB. CD47⁺ platelets remained high in both products, whereas CD154⁺ platelets transiently increased in CS-WB but remained low in CSPs.

Cold-storage differentially affects platelet in vitro characteristics across product types. While CS-WB exhibited greater functional and metabolic deterioration, both products retained viable platelet function through the end of 21-day cold storage. Larger studies are required to determine whether the observed in vitro differences translate into clinical outcomes.