(P-CB-15) Impact of Citrate-Free PAS-C on Platelet Quality During Cold Storage

Background/Case Studies: Citrate is a common component of most platelet additive solutions (PAS) for prevention of platelet aggregation. Microaggregate formation and pH under cold conditions have been shown to be negatively impacted by use of a citrate-free medium such as PAS-F. However, this medium also lacks phosphate, which may reduce buffering capacity and calcium sequestration leading to reduced cold platelet quality. Use of a PAS-C type solution, which contains phosphate, may support cold storage even in the absence of citrate. This study compares platelet quality and function during cold storage in conventional PAS-C (InterSol) versus a modified PAS-C lacking citrate only.

Study

Design/Methods: Hyperconcentrated, double dose platelets (N=5) were collected using the Amicus Separator, then split and resuspended with a mixture of autologous plasma and either InterSol (IS) or a citrate-free InterSol (CF) solution (65% PAS/35% Plasma). Initial Day 0 sampling was conducted, and products were then placed in cold storage for 21 days with sampling on Day 1, 7, 14, and 21. In vitro parameters assessed included: platelet (PLT) counts, pH, mean platelet volume (MPV), thromboelastography (TEG), platelet activation (CD62 expression, lactadherin binding), supernatant lactate dehydrogenase (LDH), supernatant glucose, total lactate, and microaggregates (qualitative). Data was analyzed by paired t-test with significance defined as p < 0.05.

Results/Findings: Platelet counts were comparable between CF and IS units throughout storage. MPV remained stable in CF units but showed a small yet significant increase in IS units beginning on Day 7. All units maintained pH above 6.2 during storage, however by Day 14, CF units exhibited a small but significant decrease in pH compared to IS units. Clot strength (TEG maximum amplitude, MA) showed a small but significant decrease in CF units by Day 14. Platelet activation, as measured by CD62 expression, was consistently and significantly lower in CF units, while lactadherin binding (phosphatidylserine expression) remained comparable between groups. Supernatant LDH levels (normalized to platelet count) were generally lower in IS units, though the difference was not always statistically relevant. No macroaggregates were observed, but microaggregates were more prevalent in the CF units throughout storage. Metabolic markers (glucose, lactate) were similar at all time points. Refer to Table 1 for summarized results at end of storage.

Conclusions: Removal of citrate led to increased microaggregate formation and reduced platelet integrity during cold storage, despite otherwise favorable activation markers and acceptable pH. PAS formulations containing citrate may be necessary to preserve platelet quality under cold storage conditions, though further studies are needed to clarify the clinical relevance of these parameters.