Influence of response shift on early patient-reported outcomes following autologous chondrocyte implantation

<p>Purpose Response shift is the phenomenon by which anindividual’s standards for evaluation change over time. Thepurpose of this study was to determine whether patientsundergoing autologous chondrocyte implantation (ACI)experience response shift.Methods Forty-eight patients undergoing ACI participated.The ‘‘then-test’’ method was used to evaluateresponse shift in commonly used patient-reported outcomemeasures (PROMs)—the SF-36 Physical Component Scale(SF-36 PCS), WOMAC, IKDC, and Lysholm. Each PROMwas completed pre- and 6 and 12 months post-surgery. At6 and 12 months, an additional ‘‘then’’ version of eachform was also completed. The ‘‘then’’ version was identicalto the original except that patients were instructed to assesshow they were prior to ACI. Traditional change, responseshift adjusted change, and response shift magnitude werecalculated at 6 and 12 months. T tests (p\0.05) were usedto compare traditional change to response-shift-adjustedchange, and response shift magnitude values to previouslyestablished minimal detectable change.</p>