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Patient-reported results as a group after ACI found unaffected by response shift
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MONTREAL — A recently presented study indicates that response shift is not a significant factor when evaluating patient-reported outcomes as a group after autologous chondrocyte implantation, but notes that response-shift may occur on a patient-by-patient basis.
“We did not see a group effect for response shift, supporting the validity of traditional pre-post outcomes reporting,” Jennifer S. Howard, PhD, ATC, said in her presentation at the International Cartilage Repair Society World Congress 2012. “Across the group, we are not misreporting or missing anything. But, if you look at patients on an individual basis, there may be something going on, which could help manage patient expectations and explain why the clinical exam may not always match up with what the patient is telling you.”
Howard and colleagues conducted their study to determine whether patients who undergo autologous chondrocyte implantation (ACI) experience response shift — a phenomenon by which an individual’s self-evaluation of a construct changes due to a change in internal standards of measurement.
“A person’s frame of reference and how they make decisions may change over time, affecting how they complete their outcomes forms. If patients are asked the same question at two different time points they may not use the same criteria to answer the question at each time point. For example, patients may recalibrate their internal pain scale following surgery. Pain that they may have considered to be an eight out of 10 before surgery, they might now rate as a five out of 10. Similarly, patients may have high expectations for a treatment and when the treatment fails to meet those expectations, they may report no improvement or even a slight decline in their condition, even when objective clinical measures may show improvement. These internal recalibrations may result in reporting treatment effects that are more a function of changes in personal standards and values than changes in physical condition.” Howard said.
The investigators studied 29 patients with an average age of 36.3 years and looked for response shift in patient-reported outcomes including the Lysholm Knee Scale, the SF-36 physical component scale, the IKDC Subjective Form and the WOMAC.
The patients completed surveys preoperatively and at the 6-month and 12-month follow-up. Patients were also asked to complete a “then” version of each survey at 6-months and 12-months that was identical to the original survey, but designed so the patients could assess how they were preoperatively. Results from these surveys were used to determine traditional change, response-shift adjusted change and response-shift magnitude at 6 months and 12 months postoperatively.
The researchers found no differences between response-shift adjusted change and traditional change scores for any of the patient-reported outcomes investigated. She noted, however, that eight patients at the 6-month mark and six patients at the 12-month mark demonstrated response-shift magnitude values greater than the minimal detectable change on at least three of the four outcome instruments.
“We did not see a big response shift across the board,” Howard said. “If you look at the literature, previous orthopedic studies looking at microfracture or total knee arthroplasty have reported a statistically significant response shift. But if you look at their values compared to our values, they are not that different, and none of the values surpass previously reported minimal detectable change values, which raises an important issue in research: What is statistically significant may not be meaningful.”
She noted that the study indicates that response shift may occur on a patient-to-patient basis, but that pre-test and post-test research designs appear to be valid approaches to evaluate the efficacy of articular cartilage treatments. – by Robert Press
Reference:
- Howard JS, Mattacola CG, Mullineaux DR, et al. Evidence of response shift in patient reported outcomes (PROs) following autologous chondrocyte implantation (ACI). Paper 25.2.2. Presented at the International Cartilage Repair Society World Congress 2012. May 12-15. Montreal.
For more information:
- Jennifer S. Howard, PhD, ATC, can be reached at the University of Kentucky College of Health Sciences, Charles T. Wethington Jr. Building Rm 206B, 900 South Limestone, Lexington, KY 40536; email: j.s.howard@uky.edu.
- Disclosure: Howard and Christian Lattermann serve as consultants for Sanofi/Genzyme Corporation, and Christian Lattermann also serves as a consultant for Zimmer Inc. This research was supported by grant number UL1RR033173 from the National Center for Research Resources (NCRR), funded by the Office of the Director, National Institutes of Health (NIH) and supported by the NIH Roadmap for Medical Research. The content is solely the responsibility of the authors and does not necessarily represent the official views of NCRR and NIH.