300 Section - Factors Predicting the Efficacy of Platelet-Rich Plasma Therapy in Knee Osteoarthritis: A Retrospective Cohort Study Based on Quantitative Complete Blood Count

Objectives : PRP injection has gained attention for treating knee osteoarthritis (KOA), but its efficacy varies and predictive factors are unknown. The complete blood count (CBC) is a quantitative, accessible, and cost-effective test that may help predict outcomes. This study aimed to retrospectively evaluate PRP therapy outcomes and explore associations with CBC indicators from blood samples taken before and after PRP preparation.

Design:

Patients with KOA who received three PRP injections and completed a 6-month follow-up between 2023 and 2025 were enrolled. The Visual Analog Scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were used to assess pain levels and functional status, respectively. Patients were dichotomized into responders and non-responders based on the minimal clinically important difference. Correlation analysis and multivariate linear regression were used to analyze the relationship between cellular parameters in whole blood and PRP with treatment outcomes. The predictive performance of these parameters was evaluated using receiver operating characteristic (ROC) curve analysis.

Results:

 A total of 140 patients (185 knees) were included, with a mean follow-up duration of 6.23 ± 0.35 months. At the final follow-up, both VAS and WOMAC scores showed significant improvement compared to baseline. Twenty-six patients were classified as non-responders. Multivariate analysis identified the lymphocyte-to-monocyte ratio (LMR) in whole blood and the platelet enrichment factor (PEF) in the PRP preparation as independent factors influencing both pain and functional improvement. The baseline LMR was significantly lower in the non-responder group compared to the responder group. ROC curve analysis indicated that the optimal cut-off value of whole blood LMR for predicting treatment response was 5.360 (sensitivity 0.779, specificity 0.642), and the optimal cut-off for PEF was 3.27 (sensitivity 0.879, specificity 0.542).

Conclusion: Pre-treatment LMR (systemic inflammation) and PEF (platelet enrichment) were associated with PRP efficacy in KOA, serving as predictive biomarkers for treatment outcome.