The effect of leucocyte concentration of platelet-rich plasma on outcomes in patients with lateral epicondylitis: a systematic review and meta-analysis

Hypothesis: The concentration of leukocytes influences the quality of platelet-rich plasma (PRP). However, there is no consensus on which type of PRP based on the concentration of leukocytes is the best for lateral epicondylitis (LE). Methods: We systematically searched the MEDLINE, Embase, and Cochrane Library databases until March 1, 2020. Studies involving randomized controlled trials, patients with LE, and treatment with PRP injections were included. PRP was classified into leukocyte-poor (LP) PRP and leukocyte-rich (LR) PRP. LR-PRP was defined as PRP with a white blood cell concentration exceeding that of whole blood (4.0–10.0 per μL³), whereas LP-PRP was defined as PRP with a lower white blood cell concentration than that of whole blood. The efficacy of PRP was assessed using the visual analog scale (VAS) and success rates. Results: Eleven randomized controlled trials (six involving LP-PRP and five involving LR-PRP) were eligible for inclusion in this review. Eight studies were included in the meta-analysis to evaluate the VAS score. Regarding short-term follow-up, there was no difference in the VAS scores between the LP-PRP and control groups (standard mean difference [SMD], 0.01; 95% confidence interval [CI], −0.29 to 0.30; P = 0.97), with no heterogeneity (I² = 0%). There was also no difference in the VAS scores between the LR-PRP and control groups (SMD, −0.19; 95% CI, −0.57 to 0.20; P = 0.34), with substantial heterogeneity (I² = 56.7%). Regarding long-term follow-up, there was no difference in the VAS scores between the LP-PRP and control groups (SMD, −0.73; 95% CI, −1.69 to 0.23; P = 0.134) with substantial heterogeneity (I² = 88.4%). The LR-PRP group had lower VAS scores than the control group (SMD, −1.06; 95% CI, −2.02 to −0.09; P = 0.032) with substantial heterogeneity (I² = 92%). In the LP-PRP group, there was no significant difference in the success rate (odds ratio, 1.08; 95% CI, 0.07–16.47; P = 0.956) with substantial heterogeneity (I² = 87.7%). In the LR-PRP group, however, the patients who received PRP had a higher success rate than those in the control group (odds ratio, 2.85; 95% CI, 1.67–4.85; P < 0.01) with substantial heterogeneity (I² = 82.9%). Conclusion: LR-PRP may provide pain relief and successful outcomes for patients with LE compared with alternative local injections. Better results were observed with the use of LR-PRP than with the use of LP-PRP.