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

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.