Effects of the start date of refrigeration on functions of delayed cold‐stored platelets

Background and Objectives The functions of cold‐stored platelets (PLTs) have recently been re‐evaluated. In Japan, cold storage may be started immediately after blood collection (Day 0, control group), after the period for improving bacterial screening sensitivity has ended (Day 2, DCS2) and after the expiration date of room‐temperature storage has ended (Day 5, DCS5). The present study investigated the effects of different cold storage start dates on PLT function. Materials and Methods Concentrated PLTs, collected using an apheresis device, were placed in an additive solution (Terumo‐platelet additive solution+, Terumo BCT) and then divided into three groups with different cold storage start dates (days 0, 2 or 5). The three groups were stored until Day 21, and various PLT function parameters—including aggregation (adenosine diphosphate [ADP] + collagen‐induced and ristocetin‐induced aggregation), viscoelasticity (maximum clot firmness [MCF], clotting time and α ‐angle) and PLT activation (CD62P, PAC‐1, CD63 and Annexin V)—were measured and compared. Results Comparisons of results until Day 14 revealed that among the PLT function parameters examined, only ADP + collagen‐induced aggregation and MCF showed a deterioration in DCS2 and DCS5. However, aggregation and MCF values in DCS2 and DCS5 on Day 10 were not markedly different from those in the control group on Day 14 (US expiration date). Conclusion PLTs stored at room temperature for 2 or 5 days after collection and then refrigerated may be preserved until Day 10.