Composition of Platelet-Rich Plasma Prepared From Knee Osteoarthritic Patients: Platelets, Leukocytes, and Subtypes of Leukocyte

Introduction: Platelet-rich plasma (PRP) has gained increasing popularity in the orthopedic field. There has been still no consensus on PRP preparation technique, thus providing a variety of final PRP products. Different preparation techniques lead to different compositions of PRP, which include platelet concentration, the number of leukocytes, and their subtypes. Here, we studied those compositions of PRP compared to whole blood samples. Methods: There were 335 participants who met the inclusion and exclusion criteria. Each participant underwent a blood drawing process to prepare PRP for their knee osteoarthritis treatment. We categorized baseline platelet concentration in whole blood samples into three groups: less than 2 x 10(5)/µL (Group 1), between 2 x 10(5)/µL and 2.99 x 10(5)/µL (Group 2), and greater than 2.99 x 10(5)/µL (Group 3). The primary outcome was reported as the platelet concentration in PRP and the ratio of platelet concentration in PRP compared to baseline whole blood samples. The secondary outcome was reported as the ratios of leukocyte, lymphocyte, and neutrophil in PRP compared to the baseline whole blood samples. Results: The average platelet concentration in PRP was 1.26 x 10(6)/µL (6.3 times higher compared to baseline whole blood samples). The mean platelet concentration of PRP in Group 1, Group 2, and Group 3 was 1.08 x 10(6)/µL, 1.38 x 10(6)/µL, and 1.71 x 10(6)/µL, respectively (p-value = 0.0001). The platelet concentration ratio of PRP condition to the baseline whole blood was 6.9, 5.8, and 4.2 in Group 1, Group 2, and Group 3, respectively (p-value = 0.0018). The average ratio of leukocytes in PRP to whole blood was 1.5. The average ratio of lymphocytes and neutrophils in PRP to whole blood was 2.0 and 0.5, respectively. Conclusion: Different baseline platelet concentrations in whole blood samples provided significantly different platelet concentrations in PRP. The baseline platelet concentration in whole blood also provided an inverse relation to the fold change of the platelet concentration in PRP. Subtypes of leukocytes changed from neutrophil-predominated in the baseline whole blood samples to lymphocyte-predominated in PRP.