Rich or Poor? Examining Platelet-Rich Plasma Leukocyte Concentration in Knee Osteoarthritis

The use of platelet-rich plasma (PRP) for the treatment of symptomatic knee osteoarthritis (OA) of various stages has grown in popularity over the years. However, there still exists substantial controversy over the optimal PRP preparation method, dosing (1 injection or multiple injections), and growth factor and leukocyte concentrations. Although limited, recent studies have suggested a possible benefit of leukocyte-poor (LP) PRP compared with leukocyte-rich (LR) PRP in knee OA1. Although there have been many studies of varying quality comparing PRP with hyaluronic acid, corticosteroids, and placebo, there have been very few studies comparing LP-PRP with LR-PRP2. In their study, Abbas et al. attempted to determine if LP-PRP or LR-PRP is preferred for the treatment of symptomatic knee OA by performing a network meta-analysis of the existing literature (including 20 randomized controlled trials and 3 prospective comparative studies) looking at the change in patient-reported outcome scores (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], WOMAC pain, visual analog scale [VAS] for pain, and International Knee Documentation Committee [IKDC]) between baseline and follow-up (minimum, 6 months).

The authors should be applauded for their work in providing the reader with a well-written and thorough analysis of an important and controversial topic. There are inherent difficulties in performing a study of this type given the substantial limitations present in the existing literature (study bias and heterogeneity in PRP preparation, administration, dosing, outcome measurements used, study design, patient OA grades, patient age, patient body mass index, patient sex, and follow-up time points). The main strengths of this study are the network meta-analysis design and bias analyses employed by the authors to control for the quality and heterogeneity of the studies included. However, these same strengths also highlight the main weaknesses of the study’s conclusions. The results of this network meta-analysis suggest that there is no clinically important difference in patient-reported outcome scores between patients receiving LR-PRP and those receiving LP-PRP for symptomatic knee OA at a short-term follow-up (mean, 9.9 months). Despite this, surface under the cumulative ranking (SUCRA) probabilities favored LP-PRP over LR-PRP for all outcome measures at all time points. So, does leukocyte concentration in PRP formulations matter in the treatment of knee OA? Probably not, but maybe? This study analyzes the best available literature on the topic, but better Level-I randomized controlled trials directly comparing LR-PRP with LP-PRP are needed.

What we do know from this study is that PRP, in general, is a safe and potentially more effective nonoperative treatment for varying levels of knee OA in the short term compared with hyaluronic acid, corticosteroids, and placebo. However, it is important to note that differences in patient age, health status, sex, and ethnicity may also result in differences in PRP humoral concentrations and efficacy despite a set leukocyte concentration (LR compared with LP)3,4. LP-PRP in an obese, 42-year-old, African American man may be very different from LP-PRP in a thin, 70-year-old, Asian woman. Moreover, PRP used in a patient with Kellgren-Lawrence (KL) grade-IV changes may not have the same efficacy or duration of effect as PRP used in a patient with KL grade-I or II changes. Therefore, the results of this network meta-analysis may not be 100% generalizable to the population based on the mean age, sex, body mass index, and KL grade of the patients included, but it is the best we have to date.