In vitro storage characteristics of platelet concentrates suspended in 70% SSP+(TM) additive solution versus plasma over a 14-day storage period

Background and Objectives The non‐paired two‐arm study compared the in vitro storage characteristics of platelets suspended as concentrates in either 100% plasma or a mixture of additive solution (SSP+?, MacoPharma, Mouveaux, France) and autologous plasma in a 70:30 ratio over a 14‐day storage period. Materials and Methods The buffy coat‐derived pooled platelet concentrates were sampled on days 1, 2, 3, 6, 8, 10 and 14 and tests performed to determine platelet morphology, function, metabolism, activation and apoptosis‐like activity. Results Swirling remained strong (score = 3) in SSP+?, whilst scores of 1 and 0 were noted for plasma units by end of storage. In contrast to units in plasma, pH levels remained above seven in SSP+? units, increasing after day 10. Percent positive expression of CD62P was similar in both groups on day 1 (median of 54% and 56% for plasma (n = 13) and SSP+? (n = 12), respectively), with SSP+? units showing a more moderate increase in activation after day 10. A progressive decrease in mitochondrial membrane potential was evident in both groups from day 1, whilst annexin V binding was relatively stable from days 1 to 3, with median values remaining below 6%. Subsequent to this, the percentage of platelets binding annexin V increased to approximately 30% by day 14. Conclusion Platelets suspended in a medium of 70:30 SSP+? to plasma ratio performed at least as well as platelets in 100% autologous plasma for up to 10 days of storage. Further, results are suggestive of an apoptosis‐like process being involved in the platelet storage lesion.