Recovery of Donor Peripheral Blood Platelet Count Following Platelet Apheresis.

BACKGROUND: Apheresis platelet collection from healthy normal blood donors can reduce the donor peripheral blood platelet concentration by 50% or more. The kinetics of peripheral blood platelet count (PLT) recovery in the apheresis donors over the first 24 hours has not been described. The objective of this study was to determine the recovery kinetics of the donor peripheral blood platelet count following apheresis platelet donation.

METHODS: Healthy apheresis platelet donors were enrolled following informed consent. The apheresis platelet collection was performed using the Gambro Trima system (Gambro BCT, Lakewood, CO) following local SOP and manufacturer’s directions for use. The minimum predicted post-count was configured in the Trima to no less than 78K plt/μL. PLT was determined pre-procedure (Pre), immediately post procedure (Post), 4–11 h (FU1) and 11–41 h (FU2) post-donation using standard methods. The PLT recovery was evaluated as the increase in PLT following the donation (Delta). The effects of study site, time of sample, and the fraction of platelets collected (Fpc) at donation on Delta were evaluated using a random effects generalized linear regression model. A full regression model of Delta as a function of study site, follow-up period and Fpc with all main and interaction effects was used to test hypotheses.

RESULTS: 548 subjects were entered into the study at 3 study sites; Pre-PLT 276±59 × 10³ plt/μL, Post-PLT 205±47 × 10³ plt/μL, Fpc 25±10%. No adverse events were reported by any subjects. Recovery of platelet count following apheresis platelet donation is variable between subjects; and the independent variables of study site, follow-period and Fpc accounted for 25% of the total variation in Delta. PLT increased 12.4±0.9 × 10³ plt/μL by the time of follow-up sampling (p=0.01), although there was no difference between PLT at FU1 (214±49 × 10³ plt/μL) and FU2 (212±47 × 10³ plt/μL; p=0.15). None of the donors reached their pre-donation platelet count during the follow-up period. There was no difference in Delta between centers (p=0.23). Fpc had a significant affect on Delta (p<0.0001); with estimated Delta of 5.2±0.9 × 10³ plt/μL at Fpc=15% and 16.0±.8 × 10³ plt/μL at Fpc=30%.

CONCLUSION: Platelet recovery following apheresis platelet donation was observed to be dependent on the fraction of platelets donated. Surprisingly, the recovery observed within the first 11 h was equivalent to that observed between 11–42 h, averaging 17.5% of the drop observed during apheresis. Recovery was not complete when observed for up to 41 h following donation in this study. Additional investigation of PLT recovery following apheresis donation is indicated to describe and differentiate the potential roles of de novo production, early pro-platelet release and platelet release from peripheral pools over the early post-donation period.