Clot formation and resolution properties of platelets during cold storage for 21 days

Cold storage (2-6°C) preserves the aggregatory and clot formation properties of platelets beyond the standard 7-day shelf life. Comparatively little is known about the effect of cold storage on clot resolution functions, which are necessary to ensure normal hemostatic balance is maintained.

Double-dose apheresis platelets (n = 8) were collected using the Trima apheresis platform (40% plasma/60% PAS-E). Platelets were sampled on Day 1 post-collection and allocated to room temperature (RT; 20-24°C) or cold storage (2-6°C). In vitro testing was performed over a 21-day period.

The coagulation profile of cold-stored platelets was better maintained throughout storage compared to RT platelets. Cold-stored platelets showed increased thrombin generation potential (faster lag time, higher peak, and increased ETP) compared to RT platelets throughout storage. By viscoelastic testing, the IN-test and EX-test clotting times (CT) were maintained over cold storage for 21 days, while the clot strength (MCF) decreased by approximately 15%. The lysis time (LT) was unchanged during cold storage. Macroscopically, less clot retraction and a higher percentage of internal lysis were observed in cold-stored platelets; however, susceptibility to external lysis was not affected.

Hemostasis requires a delicate balance between clot formation and resolution, and we have shown that the key functional properties of cold platelets stored in PAS-E are well-regulated during extended storage for 21 days.