Continuous agitation induces aggregate formation in cold-stored platelets during extended storage in platelet additive solution.

BACKGROUND AND OBJECTIVES: Reduced metabolic activity of cold-stored platelets (CSPs) has led to the assumption that agitation is not required during cold storage. However, guidelines from the Food and Drug Administration state that agitation is 'optional' and there is a degree of international variability described in the literature. The effect of agitation on the quality of CSPs stored in platelet additive solution (PAS) for an extended storage period has not been established. MATERIALS AND METHODS: Matched apheresis platelets (n = 8) in 40% plasma/60% PAS-E (SSP+) were refrigerated (2-6°C) and either non-agitated (control), continuously agitated, or periodically agitated. In vitro quality parameters were assessed at defined intervals over 21 days. RESULTS: Agitation did not alter the metabolic properties of CSPs. The abundance of platelet glycoproteins (GPIIIa, GPIbα, GPVI) decreased, while activation markers (activated GPIIb/IIIa, fibrinogen binding, P-selectin and phosphatidylserine) increased during cold storage; however, no significant differences were observed between groups. The functional capacity of CSPs was the same regardless of agitation, with no differences in aggregation response (collagen-induced and adenosine diphosphate [ADP]-induced), or viscoelastic properties (clotting time and maximum clot strength). Platelets stored with continuous agitation developed visible aggregates; which were observed in 88% of components at Day 14, and 100% of components by Day 21. Aggregates were not observed in non-agitated or periodically agitated components. CONCLUSION: Continuous agitation did not improve the metabolic or functional properties of CSPs and led to the development of aggregates. These findings confirm that non-agitated storage is best practice for CSPs stored in PAS, reinforcing the operational simplicity of cold storage.