Physical and social functioning after stroke: comparison of the Stroke Impact Scale and Short Form-36.

Background And Purpose: This study evaluated assessments of physical functioning and social functioning using the Stroke Impact Scale (SIS) and Short Form-36 (SF-36) to characterize health-related quality of life for patients after stroke.

Methods: The SIS and SF-36 were administered to 278 stroke subjects approximately 90 days after stroke. The SIS-16 and SF-36 Physical Functioning (PF) domain characterize physical function, whereas the SIS Participation and SF-36 Social Functioning (SF) domains characterize social function. Descriptive statistics and an analysis of variance were used to characterize physical and social functioning after stroke across levels of the modified Rankin Scale (MRS). Rasch analysis was used to compare the hierarchies and ranges of item difficulties in the SIS-16 and the SF-36 PF domains, as well as in the SIS Participation and the SF-36 SF domains.

Results: Item hierarchies for the SIS-16 and SF-36 PF domain demonstrate that the SIS-16 contains less difficult items that could differentiate physical function among patients with more severe limitations. Compared with the SF-36 SF domain, the item hierarchy for the SIS Participation domain contained more difficult items that could differentiate social function among patients who were more active. In contrast to SIS-16, the SF-36 PF has major floor effects. In contrast to SIS Participation, the SF-36 SF domain has major ceiling effects. Both SIS-16 and SF-36 PF were able to discriminate well among the MRS levels of 0 to 1, 2, 3, and 4. The SIS Participation domain was also able to discriminate across the MRS levels of 0 to 1, 2, and 3 to 4. On the other hand, the SF-36 SF was similar among MRS levels 0, 1, and 2 and among MRS levels 2, 3, and 4.

Conclusions: Both the physical and participation subscales of the SIS cover a wider range of item difficulty than their counterparts from the SF-36. Compared with the SF-36 PF and SF domains, the SIS-16 and SIS Participation are better able to capture physical functioning and social well-being in patients with strokes.