Minimal Clinically Important Differences and Substantial Clinical Benefit in Patient-Reported Outcome Measures after Autologous Chondrocyte Implantation

Objective We sought to determine the minimal clinically important difference (MCID) and substantial clinical benefit (SCB) associated with the Knee Injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Lysholm, and Short Form-12 (SF-12) after autologous chondrocyte implantation (ACI). Design Ninety-two patients with satisfaction surveys at a minimum of 2 years postoperatively and at least 1 repeated patient-reported outcome measure (PROM) were analysed. The MCID was determined using 4 anchor-based methods: average change, mean change, minimally detectable change, and the optimal cutoff point for receiver operating characteristic (ROC) curves. If an anchor-based method was not applicable, standard deviation-based and effect size-based estimates were used. SCB was determined using ROC curve analysis. Results The 4 anchor-based methods provided a range of MCID values for each PROM (11-18.8 for the KOOS pain, 9.2-17.3 for the KOOS activities of daily living, 12.5-18.6 for the KOOS sport/recreation, 12.8-19.6 for the KOOS quality of life, 10.8-16.4 for the IKDC, and 6.2-8.2 for the SF-12 physical component summary). Using the 2 distribution-based methods, the following MCID value ranges were obtained: KOOS symptom, 3.6 to 8.4; the Lysholm, 4.2 to 10.5; and the SF-12 mental component summary, 1.9 to 4.6. SCB was 30 for the KOOS sport/recreation and 34.4 for the IKDC, which most accurately predict substantial improvement. No significant association was noted between SCB achievement and the baseline PROMs. Conclusion The MCID and SCB determined in our study will allow interpretation of the effects of treatment in clinical practice and trials. Given the varied MCID values in this study, standardisation of the most appropriate calculation methods is warranted.