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

Area of Science:

• Psychometrics
• Health Outcomes Research
• Measurement Theory

Background:

• Existing definitions and models of response shift present theoretical challenges.
• Clarification is needed to advance empirical investigation in this field.

Purpose of the Study:

• To propose a more specific formal definition of response shift.
• To introduce a revised theoretical model for understanding response shift.
• To address existing predicaments and stimulate empirical research.

Main Methods:

• Critical assessment of existing literature through international collaboration.
• Development of a formal definition distinguishing measures from constructs.
• Construction of a revised theoretical model with delineated paths and assumptions.

Main Results:

• Identified three key predicaments in current response shift literature.
• Defined response shift as observed change not explained by target construct change.
• Proposed a model differentiating measures (e.g., patient-reported outcome measures) from target constructs (e.g., quality of life) at multiple time points.

Conclusions:

• The refined definition and model aim to advance response shift theory.
• The model is designed for empirical examination of its assumptions and relationships.
• Future research should empirically test the proposed model's components.