Purpose: Response shift is the phenomenon by which an individual's standards for evaluation change over time. The purpose of this study was to determine whether patients undergoing autologous chondrocyte implantation (ACI) experience response shift. Methods: Forty-eight patients undergoing ACI participated. The "then-test" method was used to evaluate response shift in commonly used patient-reported outcome measures (PROMs)-the SF-36 Physical Component Scale (SF-36 PCS), WOMAC, IKDC, and Lysholm. Each PROM was completed pre- and 6 and 12 months post-surgery. At 6 and 12 months, an additional "then" version of each form was also completed. The "then" version was identical to the original except that patients were instructed to assess how they were prior to ACI. Traditional change, response shift adjusted change, and response shift magnitude were calculated at 6 and 12 months. T tests (p < 0.05) were used to compare traditional change to response-shift-adjusted change, and response shift magnitude values to previously established minimal detectable change. Results: There were no differences between traditional change and response-shift-adjusted change for any of the PROMs. The mean response shift magnitude value of the WOMAC at 6 months (15 ± 14, p = 0.047) was greater than the previously established minimal detectable change (10.9). The mean response shift magnitude value for the SF-36 PCS at 12 months (9.4 ± 6.8, p = 0.017) also exceeded the previously established minimal detectable change (6.6). Conclusions: There was no evidence of a group-level effect for response shift. These results support the validity of pre-test/post-test research designs in evaluating treatment effects. However, there is evidence that response shifts may occur on a patient-by-patient basis, and scores on the WOMAC and SF-36 in particular may be influenced by response shift. Level of evidence: II.
|Number of pages||9|
|Journal||Knee Surgery, Sports Traumatology, Arthroscopy|
|State||Published - Sep 2014|
Bibliographical noteFunding Information:
This publication was supported by the National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health, through Grant UL1TR000117. Additionally, this work was supported by a grant from the University of Kentucky COM Physician Scientist Clinical Scholar Award, the American Orthopaedic Society for Sports Medicine (AOSSM) Career Development Award, and the National Institute of Health (NIH) (1K23AR060275-01A1). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
- Articular cartilage
- Chondrocyte transplantation
- Outcomes assessment
- Response shift
ASJC Scopus subject areas
- Orthopedics and Sports Medicine