Response shift in patient-reported outcomes: definition, theory, and a revised model

Abstract

Purpose The extant response shift definitions and theoretical response shift models, while helpful, also introduce predicaments and theoretical debates continue. To address these predicaments and stimulate empirical research, we propose a more specific formal definition of response shift and a revised theoretical model. Methods This work is an international collaborative effort and involved a critical assessment of the literature. Results Three main predicaments were identified. First, the formal definitions of response shift need further specification and clarification. Second, previous models were focused on explaining change in the construct intended to be measured rather than explaining the construct at multiple time points and neglected the importance of using at least two time points to investigate response shift. Third, extant models do not explicitly distinguish the measure from the construct. Here we define response shift as an effect occurring whenever observed change (e.g., change in patient-reported outcome measures (PROM) scores) is not fully explained by target change (i.e., change in the construct intended to be measured). The revised model distinguishes the measure (e.g., PROM) from the underlying target construct (e.g., quality of life) at two time points. The major plausible paths are delineated, and the underlying assumptions of this model are explicated. Conclusion It is our hope that this refined definition and model are useful in the further development of response shift theory. The model with its explicit list of assumptions and hypothesized relationships lends itself for critical, empirical examination. Future studies are needed to empirically test the assumptions and hypothesized relationships.

Performance of a Rasch-based method for group comparisons of longitudinal change and response shift at the item level in PRO data: A simulation study

“…Consequently, longitudinal PRO data may not be comparable over time due to lack of measurement invariance, also called response shift (RS) whose definition has been recently updated by Vanier et al [5]. RS is considered to be a "special case of violation of the principle of conditional independence when observed change is not fully explained by target change" (i.e.…”

“…RS is considered to be a "special case of violation of the principle of conditional independence when observed change is not fully explained by target change" (i.e. change in the construct of interest) as a result of "a change in meaning in self-evaluation of a target construct" [5] . Violation of the principle of conditional independence may be due to how RS manifests itself through recalibration (a change in one's internal standards), reprioritization (a change in one's values), and reconceptualization related to one's redefinition of the target construct [6].…”

What should progress in response-shift research look like?

“…Clearly, there is a growing consensus among researchers that response-shift phenomena are central to any understanding of quality of life (QOL). However, as this series of papers clearly states, much of the uncertainty about how to align and reconcile different definitions and methods remains unclear [1][2][3][4]. Twenty-five years after the initial work on response shift [5], it feels less than satisfactory to leave these as unresolved.…”

“…The appraisal model offers testable pathways to explain the unexpected impact of changes in health states and other life events. Influences of demographic, clinical and psychosocial antecedents listed in Vanier et al's [2] table of related domains are also expected to be mediated by appraisal.…”

“…Both the Vanier et al and Sawatzky et al papers promote a perspective that response shift is a form of bias in measurement [2,3]. This position is difficult to reconcile with an understanding of response shift as meaningful change.…”