Measuring Stroke Impact with SIS: Construct Validity of SIS Telephone Administration
Objectives: The purpose of this study was to examine the construct validity of the Stroke Impact Scale (SIS) using telephone mode of administration. Methods: Stroke patients were identified using national VA administrative data and ICD-9 codes in 13 participating VA hospitals. Stroke was confirmed by reviewing electronic medical records. Patients were administered SIS by telephone at 12-weeks post-stroke, and administered the Functional Independence Measure (FIM) and SF-36V at 16 weeks post-stroke. The instrument’s convergent validity and its ability to differentiate between groups of stroke patients with different disability levels were examined using Pearson’s correlations and Kruskal–Wallis one way ANOVA tests. Results: All the relevant relationships yielded high correlation coefficients with statistical significance: 0.86 for FIM-motor vs. SIS-ADL, and 0.77 for PF in SF-36V vs. SIS-PHYSICAL. The SIS presented better score discrimination and distribution for different severity of stroke than FIM and SF-36V without severe ceiling and floor effects. Kruskal–Wallis tests showed the Physical Component Score of SF-36V did not discriminate any disability levels. Physical functioning (PF) in SF-36V, FIM-motor, SIS-PHYSICAL, SIS-16, and SIS-ADL showed better discrimination in person’s functioning. The pairwise comparisons showed that SIS-PHYSICAL, SIS-16, and SIS-ADL discriminated more Rankin levels than FIM-motor and PF in SF-36V. Conclusions: SIS telephone survey had superior convergent validity and was better at differentiating between groups of stroke patients with different disability levels than the FIM and SF-36V with no evidence of ceiling and floor effects. Telephone administration of SIS would be a useful and cost-effective method to follow-up community dwelling veterans with stroke.