Health-related quality of life after stroke: does response shift occur in self-perceived physical function?

Abstract

Objective: To determine whether response shift (a change in the self-perceived meaning of health-related quality of life [HRQL]) was present in a model of physical function over time poststroke.

Design: Secondary data analysis of a longitudinal observational study.

Setting: Community.

Participants: A consecutive sample of stroke survivors (N=677) at 1, 3, 6, and 12 months poststroke was included. Sixty-seven individuals were approached, but refused. Sixty-seven percent completed the study at 12 months. Mean age was 68 years; 45% of the participants were women.

Interventions: Not applicable.

Main outcomes measures: The Medical Outcomes Study 36-Item Short-Form Health Survey, Euroqol, Stroke Impact Scale, Preference-Based Stroke Index, and the Health Utilities Index.

Results: Structural equation modeling was used to identify response shift. A chi-square difference test between constrained and unconstrained longitudinal models suggested the presence of response shift in the data. Reprioritization response shift, a change in relative importance of domains, was observed for physical activites. Recalibration response shift, a change in internal standards of measurement, was observed in physical activities, stairs, walking, and hand function.

Conclusions: Response shift has implications for the measurement of change in physical function. Measures that focus on difficulty in task performance may be sensitive to response shift, resulting in a change in perceived HRQL over time. This has implications for choosing self-perceived or performance-based measures to detect change in physical function.