Key result
Platelet function measured by PFA-100 closure time showed significant circadian variation, peaking at 2:00 h (192.0 s) and reaching a trough at 8:00 h (140.1 s; p=0.004).
Why the study?
Does platelet function measured by PFA-100 exhibit circadian variation in healthy volunteers?
Observational
Does platelet function measured by PFA-100 exhibit circadian variation in healthy volunteers?
Absolute Event Rate: 192% vs 140.1%
p-value: p=0.004
Platelet function measured by PFA-100 demonstrates a circadian rhythm, with highest reactivity (shortest closure time) in the morning at 8:00 h.
Morning platelet hyperreactivity may heighten ischemic risk; leaves open whether chronotherapy improves outcomes in observational data.
The circadian rhythm plays an important role in the physiology and pathophysiology of the human being. Previous investigations revealed a circadian rhythm also in platelet function but these investigations have been limited to optical aggregometry with platelet-rich plasma and low shear stress. The aim of the present study was to further elucidate the impact of the circadian rhythm on platelet function using whole blood at high shear rates. Platelet function determined with the platelet function analyzer PFA-100 and concentration of fibrinogen and factor VIII activity were measured in healthy volunteers during day and night time, and even at shorter intervals (8:00, 12:00, 16:00, 20:00, 22:00, 0:00, 2:00, 4:00, 6:00 h). The mean peak closure time of the collagen/epinephrine cartridge of the PFA-100 was maximal at 2:00 h (192.0 +/- 57.4 s) and declined to the trough value at 8:00 h (140.1 +/- 33.4 s) (p = 0.004). This was paralleled by data from the collagen/ADP cartridge (22:00 h: 99.1 +/- 38.5 s/2:00 h: 81.3 +/- 16.7 s; p = 0.049). Concentration of fibrinogen and factor VIII activity were lowest during night time (22:00-4:00 h). These findings demonstrate a circadian rhythm in platelet function as measured with the PFA-100. The PFA-100 seems to be an appropriate tool to describe circadian alterations and is easier to use than optical aggregometry in analogous studies.
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Feuring et al. (2009) conducted an observational in Healthy volunteers. Night time (2:00 h) vs. Morning (8:00 h) was evaluated on Mean peak closure time of the collagen/epinephrine cartridge of the PFA-100 (p=0.004). Platelet function measured by PFA-100 closure time showed significant circadian variation, peaking at 2:00 h (192.0 s) and reaching a trough at 8:00 h (140.1 s; p=0.004).
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