The count of PSLPs increases during storage of apheresis PLTs at RT. (A) PSLP counts measured by Coulter counter for 5 individual apheresis PLT products. (B) FC scatter plots of PSLPs at days 1, 3, 5, and 7 of storage. (C) Representative FC size distribution plot of PSLPs on day 5 storage (red histogram represents silica standard size particles). FC-based counts of small (D) and large (E) PSLPs up to day 7 of storage (N = 12). FC data are expressed as the fold change in the count of small and large PEVs normalized to that of the day 1 platelet bag (mean ± SE) (¤P < .001; #P < .01; ∗P < .05; N = 12). (F) Nanoparticle tracking analysis (NTA) of PSLPs (N = 5). (G) Representative NTA histogram shows the broad size distribution of PSLPs.