This letter to the editor was written by Brian J. Cole, MD, MBA, and Lisa A. Fortier, DVM, PhD.
We would like to thank Laura Miller of Becker’s Orthopedic, Spine and Pain Management (August Issue) for her commentary on our recently published article "Growth Factor and Catabolic Cytokine Concentrations are Influenced by the Cellular Composition of Platelet-Rich Plasma" (Am J of Sports Medicine, August, 2011 by Emily A Sundman, Brian J Cole, MD, MBA and Lisa A Fortier, DVM, PhD). We find it necessary, however, to clarify the clinical significance of our results. The novel information revealed in the article is that leukocyte counts are directly correlated to catabolic cytokine concentrations and these catabolic cytokines have known detrimental effects on musculoskeletal tissues. It is no surprise nor is it novel information that Biomet PRP has more growth factors than Arthrex ACP because Biomet PRP simply has more platelets than Arthrex ACP and more platelets means more growth factors. The platelet concentration, is, in part related to the volume of the initial blood draw among other factors. Even though Biomet PRP has more growth factors than Arthrex ACP, it was inaccurately stated by Ms. Miller that PDGF in Arthrex ACP was lower than peripheral blood. The take home point of the manuscript is that leukocyte concentration should be considered in addition to platelets and growth factor concentration when considering PRP application. The paradigm has shifted away from "more is better" relative to growth factor concentration and scientists look at PRP as a composite of all blood elements as being important for the successful clinical application of PRP. This clarity should be emphasized to avoid inaccurate conclusions drawn from our work.