Minimal Clinically Important Difference and Patient Acceptable Symptom State in Patients With Knee Osteoarthritis Treated With PRP Injection

Abstract

Background: Although several injection-based treatments have been proposed to address knee osteoarthritis (OA), it is often difficult to understand the clinical relevance of the obtained results. The psychometric measures of minimal clinically important difference (MCID) and Patient Acceptable Symptom State (PASS) were developed to better interpret study findings. Purpose: To establish the MCID and the PASS for the International Knee Documentation Committee (IKDC) Subjective score and the Knee injury and Osteoarthritis Outcome Score (KOOS) in patients treated with intra-articular platelet-rich plasma (PRP) injections for knee OA. Study Design: Case series; Level of evidence, 4. Methods: This study included 215 patients with knee OA (68% men, 32% women; age, 53.2 ± 11.3 years; body mass index, 26.8 ± 4.3 kg/m2) who underwent intra-articular PRP injections. Patients were assessed through the IKDC Subjective score and KOOS subscales, and the MCID and the PASS for both measures were independently calculated at 6 and 12 months post-injection. The MCID was calculated using the value equal to half of the standard deviation of the overall cohort improvement. The PASS was assessed using a 2-point scale (satisfied or not satisfied), with threshold values being detected through a receiver operating characteristic curve analysis and the Youden index to maximize the sensitivity and the specificity of the threshold values. Results: All scores improved significantly from baseline to 6 months and baseline to 12 months (P