Review of Dohan Eherenfest et al. (2009) on “Classification of platelet concentrates: From pure platelet-rich plasma (P-PRP) to leucocyte- and platelet-rich fibrin (L-PRF)”

This classic discusses the original publication of Dohan Eherenfest et al. on "Classification of platelet concentrates: from pure platelet-rich plasma (P-PRP) to leucocyte- and platelet-rich fibrin (L-PRF)", in which the authors propose four categories of platelet concentrates depending on their leukocyte and fibrin content (P-PRP, leucocyte- and platelet-rich plasma (L-PRP), pure platelet-rich fibrin (P-PRF), and L-PRF) to group a "jungle" of products in which the term platelet-rich plasma (PRP) was used indistinctly. They were able to identify common factors such as: (1) the use of anticoagulant and immediate centrifugation of the blood after its collection, (2) most preparation techniques allowed platelet concentrate preparation within an hour, (3) the centrifugation aimed to separate the blood in layers that would allow the extraction of specific fractions, and (4) the product was activated with thrombin or calcium chloride. The reviewed manuscript has been listed among the most cited PRP articles in regenerative medicine, with more than 800 citations, driving the current scientific research and clinical practice by categorizing L-PRP and P-PRP (now, leukocyte-poor PRP). The classification has also opened the door to understanding intrinsic biological mechanisms between the platelets, leukocytes, fibrin, and growth factors, later considered for studying the proliferation and differentiation of cells in different tissues affected by PRP. Since the initial classification of platelet concentrates, several other classification systems have been proposed and published in the current literature, such as the PAW, Mishra, PLRA, DEPA, MARSPILL, etc. These classifications have identified important aspects of PRP that affect the biological composition and, ultimately, the indications and outcomes. To date, there is still a lack of standardization in sample preparation, cohort heterogeneity, and incomplete reporting of sample preparation utilized, leading to a lack of clarity and challenging researchers and clinicians.