Influence of response shift on evaluations of change in patient-reported outcomes.

The aims of this paper are to review the theoretical history of response shift and selected methodological approaches used to assess response shift, and to highlight the important next steps for research in this field. Patient-reported outcomes (PRO), such as health-related quality of life, play a central role in evaluating the impact of illness and healthcare interventions. As individuals experience changes in health or adapt to illness, their perspective and standards of well-being often fluctuate over time. Evaluations of change in PRO that do not account for this response shift effect may result in misleading conclusions about the effectiveness of interventions or clinical care. Despite important advances in response shift research over the past 10 years further work is needed to address challenges in the field that have hindered assessments of the clinical significance of response shift. This will include testing and comparison of methodological approaches that have yielded contradictory results, and triangulation of methodological approaches using quantitative and qualitative assessments. Identifying an approach that can evaluate response shift at the individual level will enrich the information derived from PRO assessments used for monitoring the impact of clinical care, tailoring individual treatments, and evaluating the effectiveness of healthcare interventions.