Stacking platelet bags: A practical storage configuration for maintaining platelet quality during cold storage

As cold-stored platelets (CSPs) are being integrated into clinical practice, it is necessary to determine the storage practices that best support platelet quality while remaining operationally feasible. Platelet components are traditionally stored at room temperature, in a single layer, to facilitate gas exchange. The reduced metabolic activity of CSPs may allow for the storage of platelet bags in different configurations, offering improved space efficiency in blood bank refrigerators.

Matched apheresis platelets (n = 8) in 40% plasma/60% PAS-E (SSP+) were refrigerated (2-6°C) in one of the following storage configurations: single layer (control), stored upright, or stacked flat. In vitro quality parameters were assessed at defined intervals over storage for 22 days.

Visible aggregates were identified in 75% of components that were stored upright between days 15 and 22, while no aggregates formed in control or stacked components during the storage period. Platelet components stored upright were more activated at maximal expiry, with greater loss of platelet glycoproteins (GPIbα and GPVI), and an increase in activation markers (P-selectin, annexin-V, and CD61⁺/annexin-V⁺ extracellular vesicles). Comparatively, no significant differences in platelet activation markers were observed in stacked platelets at the end of storage compared to controls. No differences in the metabolic or functional capacity of CSPs were observed, regardless of storage configuration.

Platelet components stored upright were more activated and prone to aggregate formation over 22 days of storage. In contrast, stacking is a practical storage option that preserves platelet quality while minimizing space requirements in refrigerators and cool rooms.