Variation in Platelet Activation State in Pre-Donation Whole Blood: Effect of Time of Day and ABO Blood Group

Abstract

BackgroundWhilst there has been investigation into the effect of time of the day on platelet activation and function in healthy individuals, there is a lack of studies in the literature to examine this relationship among platelet donors.MethodsWe assessed the extent of platelet activation by percentage of platelets with surface-expressed P-selectin and flow cytometry in samples of whole blood from a group of qualified platelet donors (n = 84).ResultsThe mean (SD) percentage of activated platelets in the pre-donation blood samples was 1.85 ± 1.57% (range 0.2–7.5%). In univariate analyses, the percentage of activated platelets was significantly and inversely correlated with the collection time (ie, the time of day blood samples were collected) (r = –0.35, p = 0.001) and positively correlated to mean platelet volume (MPV) (r = 0.29, p = 0.008). A weaker positive correlation was also observed with ABO blood group (r = 0.228, p = 0.036). Analysis of the collection time as a categorical variable showed a greater degree of activated platelets in samples collected between 8:00 h and 10:00 h than in samples collected during the hours of >10:00 h ≤14:00 h (2.5 ± 1.8 versus 1.1 ± 0.74, p < 0.001). In the adjusted linear regression model, collection time was a significant independent predictor of platelet activation state in whole blood (β = –0.26; p < 0.001), as did ABO blood group (β = 0.55; p = 0.019).ConclusionOur results show that collection time is the most important predictor of platelet activation state in pre-donation whole blood among platelet donors. This work may have implications for optimizing the timing of platelet donation.