(P-BC-11) Aggregation in cold-stored platelet products is not associated with storage shelf style or label orientation.

The FDA has approved cold-stored platelets (CSP) stored out to 14 days for use in patients with active bleeding when conventional (room temperature stored platelets, RTP) are unavailable for transfusion. Cold storage is known to promote aggregation, and studies have shown that unlike RTP, CSP do not need to be stored with agitation. As CSP are stored in gas permeable bags, we investigated whether additional storage conditions, such as shelving style or label orientation, affect CSP aggregation.

Study

Design/Methods:

Single donor apheresis platelet units were collected (N=17, Trima 100% plasma) per Vitalant procedures and IRB approval. For each unit, equal volumes (~30 mL) were aseptically transferred to four small volume platelet storage bags (10% scale of standard storage bags) to create four mini-platelet units per donor. These four bags were each stored in a different condition: (i) perforated shelving, label down, (ii) perforated shelving, label up, (iii) solid shelving, label down, and (iv) solid shelving, label up. Units were stored for 14 days at 1-6°C, then visually scored for aggregation (1, none; 2, ~10 aggregates (“agg”), ≤1 mm; 3, ~50 agg, 1-4 mm; 4, ~100 agg, ≥4mm), and assayed for platelet count, mean platelet volume (MPV), immature platelet fraction (IPF%), and metabolic parameters (pH, glucose, lactose, bicarbonate). A subset of these units (N=11) was tested for surface marker expression (CD62P, CD41/61, CD63, phosphatidylserine), thrombin generation (ETP, lagtime, peak), aggregation (agonists: ADP, Collagen, Thrombin), and occlusion under physiologically relevant flow conditions. Categorical data were analyzed by Fisher’s exact test; continuous data analyzed by two-way ANOVA.

Results/Findings:

Aggregation occurred in 35% (12 of 34) of units stored on solid shelves and 44% (15 of 34) of units stored on perforated shelves (p=0.62), and in 41% (14 of 34) of units stored label down and in 38% (13 of 34) of units stored label up (p >0.99). Aggregation occurrence varied more with respect to donor (CV of 116%) than storage condition (CV of 14%). Intra-donor aggregate phenotype was conserved as the average number of different scores per donor was 1.4 (min 1 – max 4), and score occurrence across all bags was: 1, 60.3%; 2, 13.2%; 3, 4.5%; 4, 22%. While units stored on solid shelves had statistically significant different values for MPV, IPF%, and metabolic parameters compared to perforated shelves, the absolute/physiological differences between the two conditions were unremarkable. Moreover, there were no differences in surface receptor expression or measures of intrinsic hemostatic function for units stored in the four different conditions.

Conclusions:

Aggregation in CSP units was not enhanced by any specific storage condition and appears to be dependent on donor. Shelf style and label placement did not impact CSP aggregation or hemostatic function.