Discriminant Validity of the Stroke Impact Scale
Purpose: The purpose of this study was to determine the discriminant validity of the Stroke Impact Scale (SIS) by comparing function and quality of life in stroke patients to assessments from stroke-free community dwelling elderly. Methods: The SIS was administered at 90 to 120 days post-stroke to subjects who participated in the Kansas City Stroke Registry (KCSR). The same impact scale was also administered cross-sectionally to community dwelling elderly who were recruited from primary care clinics for participation in an ongoing prospective study of health and function (Merck). All subjects were queried for responses to 64 items of the SIS including eight domains: strength, memory and thinking, emotion, communication, ADL/IADL, mobility, upper extremity, and social participation. Regression analyses were used to examine differences between stroke patients and stroke-free elderly in each of the eight SIS domains while controlling for demographics and comorbidities. Results: One hundred and sixty KCSR subjects and two hundred and forty-three subjects from the Merck study were included in the present analysis. The mean ages were 73±10.1 and 74±5.1, respectively. Gender and race were similar in both groups. The 90-days post-stroke mean Barthel ADL was 80±23 in the stroke patients. Mean scores of all 8 SIS domains were significantly lower in stroke patients than those in the stroke-free community dwelling elderly even after controlling for differences in age and comorbidities (all p values < 0.0001). Mean scores of the 7 SIS domains (except strength), even in stroke patients who had Barthel ADL > 90 at 90-days post-stroke, remained lower than those in the stroke-free community dwelling elderly (p values < 0.01). Conclusion: The SIS was able to discriminate well between stroke patients with disability and stroke-free elderly subjects. Patients who had recovered basic ADLs continued to have residual disability and impaired quality of life when compared to non-stroke patients.