Abstract
Importance: Because the psychometric evidence supporting the use of the Stroke Impact Scale–16 (SIS–16) is limited, an examination of its psychometric properties is warranted.
Objective: To evaluate the psychometric properties of the SIS–16 using Rasch analysis.
Design: Secondary data analysis of responses to the SIS–16 from the published Field Administration of Stroke Therapy–Magnesium Trial database.
Setting: Emergency medical system agencies and acute care receiving hospitals.
Participants: A total of 1,010 people with stroke.
Outcomes and Measures: We examined the item difficulty hierarchy, item fit, person–item match, separation index, person reliability coefficient, and ceiling and floor effect of the SIS–16.
Results: The item “climb a flight of stairs” was the most difficult, and “sit without losing balance” was the easiest. Four items misfit the Rasch partial-credit measurement model. Overall, the average patient ability estimate of 2.1 logits (SD = 2.0) was higher than the average item difficulty estimate of 0.0 logits (SD = 1.1). With a separation index of 2.85, the SIS–16 can differentiate people into 4.1 statistically distinct strata. The person reliability coefficient was .89. Given that 24.2% (n = 244) obtained the maximum score and 0.2% (n = 2) obtained the minimum score, the SIS–16 had a ceiling effect in this patient sample.
Conclusions and Relevance: Results partially support the validity and clinical use of the SIS–16 in subacute stroke clinical settings. Further research is warranted to examine the psychometric properties of the SIS–16 in patients with chronic stroke.
What This Article Adds: Our results partially support the use of the SIS–16 in clinical and research settings.
