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

Abstract

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 10⁵/µL (Group 1), between 2 x 10⁵/µL and 2.99 x 10⁵/µL (Group 2), and greater than 2.99 x 10⁵/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 10⁶/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 10⁶/µL, 1.38 x 10⁶/µL, and 1.71 x 10⁶/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.

Keywords: knee osteoarthritis/ koa; leukocyte-rich prp; neutrophil-leukocyte; plasma therapy; platelet-rich plasma/ prp.

Figure 1. PRP preparation tubes.

The red tubes are for the first spinning process. The yellow tube is for the second spinning process. The green tube is for platelet-rich fibrin preparation. PRP: platelet-rich plasma

Figure 2. Box plot showing platelet concentration in PRP categorized by groups according to the baseline platelet concentration in whole blood.

The median platelet concentration in the PRP of each group is shown. The Kruskal-Wallis test was used to test the significant difference in platelet concentration in PRP among the three groups. Platelet concentration in the PRP among the three groups was statistically significantly different (p-value = 0.0001). Comparisons between every two groups were also done. A statistically significant difference was found between groups 1 and 2, and groups 1 and 3 (p-value < 0.0001, = 0.005, respectively). Comparison between groups 2 and 3 did not show a statistically significant difference (p-value = 0.07). We considered a p-value of < 0.05 significant. PRP: platelet-rich plasma

Figure 3. Box plot of the ratio of platelet concentration in PRP to baseline whole blood samples categorized by groups according to baseline whole blood platelet concentration.

The median of the ratio of platelet concentration in each group is shown. The Kruskal-Wallis test was used to test the significance among the three groups. The ratio of platelet concentration among three groups was statistically significantly different (p-value = 0.0018). Comparisons between every two groups were also done. A statistically significant difference was found between groups 1 and 2 (p-value = 0.0004). Comparisons between groups 1 and 3 and groups 2 and 3 were not found to be statistically significantly different (p-value = 0.05, = 0.228 respectively). We considered a p-value of < 0.008333 significant. PRP: platelet-rich plasma

Figure 4. Box plot showing the ratio of leukocytes in PRP to baseline whole blood samples categorized by groups according to baseline whole blood platelet concentration.

The median of the ratio of leukocytes in each group is shown. The Kruskal-Wallis test was used to test the significance among the three groups. The ratio of leukocytes among the three groups was not statistically significantly different (p-value = 0.21). We considered a p-value of < 0.008333 significant. PRP: platelet-rich plasma

Figure 5. Box plot showing the ratio of lymphocytes in PRP to baseline whole blood samples categorized by groups according to baseline whole blood platelet concentration.

The median of the ratio of lymphocytes in each group is shown. An ANOVA test was used to determine the significance among the three groups. The ratio of lymphocytes among the three groups was not statistically significantly different (p-value = 0.76). We considered a p-value of < 0.008333 significant. PRP: platelet-rich plasma

Figure 6. Box plot showing the ratio of neutrophils in PRP to baseline whole blood samples categorized by groups according to baseline whole blood platelet concentration.

The median of the ratio of neutrophils in each group is shown. The Kruskal-Wallis test was used to test the significance among the three groups. The ratio of neutrophils among the three groups was not statistically significantly different (p-value = 0.14). We considered a p-value of < 0.008333 significant. PRP: platelet-rich plasma