Marx one of the pioneers of PRP defined it quite simply: "it is a volume of autologous plasma that has a platelet concentration above baseline". (Marx, Implant Dentistry Dec. 2001, pp. 225-228) There have been other attempts to specific what define PRP but I think this one is the best.
I would add that PRP naturally is unactivated. In his paper, Dr. Marx states that activation of platelet results 70% of the stored growth factors being secreted with in 10 minutes and close to 100% within the first hour. That makes it clear that PRP should NOT be activated until it is ready to be used. As I have consistently suggested, PRP should not be activated at all except in vivo by the collagen that is abundant within most connective tissues.
Any comments on this paper would be appreciated.