Post-Transfusion Viability of 7-Day Stored Platelet (Plt) Concentrates Prepared after An Overnight Hold of Whole Blood (WB) at 22°C

Background: Currently, plt concentrates have to be prepared within 8 hours of WB blood collection. An overnight hold of the WB at 22°C would provide several advantages to blood centers: 1) plt concentrates could be prepared from every unit of WB regardless of the distance from the collection site to the processing center; and 2) plt concentrates could be processed on a single shift which would reduce operating costs. However, there is no data available on the post-storage in vivo viability of plt-rich plasma (PRP) prepared plt concentrates that have been isolated after 22°C WB storage beyond 8 hours.

Methods: Plt concentrates were prepared from WB within 1 hour of collection or after the WB had been stored at 22°C for 22 ± 2 hours. Two methods of maintaining the extended stored WB at 22°C before preparing plt concentrates were evaluated: 1) a WB unit was placed on a Compocool plate (Fresenius Corporation, Hamburg, Germany) in a container; or 2) a WB unit was placed in a 22°C incubator. All three types of plt concentrates were stored for 7 days, and, on day 7, fresh plts were prepared from a 43 ml WB sample drawn from the same volunteer donor. The stored and fresh plts were alternately labeled with ⁵¹Cr or ¹¹¹In in sequential donors. Following simultaneous transfusion of the donor’s fresh and stored plts, serial blood samples were drawn to determine the recovery and survival of each donor’s stored compared to their fresh plts. The FDA has proposed acceptance criteria for post-storage plt viability: 1) stored plt recoveries should be 66% of the same donor’s fresh plt recoveries; and 2) stored plt survivals should be 58% of the same donor’s fresh plt survivals.

Results: There were no significant differences in donor plt counts nor in fresh plt recoveries and survivals among the 32 donors who participated in the 3 studies (see table). Donor plt counts averaged 248,000 ± 13,000/μl, fresh plt recoveries averaged 63 ± 13%, and survivals 8.2 ± 1.5 days. There were no significant differences in any pre- or post-storage plt measurement based on how the WB was stored overnight at 22°C. However, combining all of the data from the plts prepared after an overnight hold of the WB, every plt parameter improved compared to plt concentrates prepared within 1 hour of donation. The plt counts of the concentrates were significantly increased from 6.2 ± 3.5 to 8.6 ± 2.2 × 10¹⁰ (p=0.02). Plt recoveries increased from 43 ± 13% to 49 ± 12%, plt survivals from 4.1 ± 1.5 days to 4.7 ± 1.3 days, and both the percentage of stored vs fresh plt recoveries increased from 72 ± 11% to 75 ± 11% and survivals from 51 ± 16% to 58 ± 13%, respectively, for plt concentrates prepared within 1 hour of WB collection compared to plt concentrates prepared after extended WB storage. However, none of these plt viability measurements were statistically significantly different.

Conclusions: Storing WB for 22 ± 2 hours at 22°C before preparing PRP plt concentrates vs preparing PRP plt concentrates within 1 hour of WB donation significantly increases the yield of plts in a concentrate by 43% while concurrently improving all measures of 7-day post-storage plt viability. With an overnight hold of the WB, both stored plt recoveries and survivals meet the proposed FDA criteria for post-storage plt viability. In contrast, only plt recoveries meet the proposed post-storage viability criterion for the short-term held WB. In summary, these data document that an overnight hold of the WB, rather than being possibly detrimental, actually improves both the quantity as well as the quality of plts in a PRP plt concentrate.

IN VIVO RADIOLABELED AUTOLOGOUS PLATELET RECOVERIES AND SURVIVALS OF PRP PLATELET CONCENTRATES STORED FOR 7 DAYS