Derivation and Validation of a Modified Short Form of the Stroke Impact Scale

Abstract

Background The Stroke Impact Scale ( SIS ) is a stroke‐specific, quality of life measure recommended for research and clinical practice. Completion rates are suboptimal and could relate to test burden. We derived and validated a short form SIS (SF‐SIS). Methods and Results We examined data from the Virtual International Stroke Trial Archive, generating derivation and validation populations. We derived an SF ‐ SIS by selecting 1 item per domain of SIS , choosing items most highly correlated with total domain score. Our validation described agreement of SF ‐ SIS with original SIS and the SIS ‐16 and correlation with Barthel Index, modified Rankin Scale, National Institutes of Health Stroke Scale, and Euro‐QoL 5 dimensions visual analog scales. We assessed discriminative validity (associations between SF ‐ SIS and factors known to influence outcome [age, physiological parameters, and comorbidity]). We assessed face validity and acceptability by sharing the SF ‐ SIS with a focus group of stroke survivors and multidisciplinary stroke healthcare staff. From 5549 acute study patients (mean age 68.5 [ SD 13] years, mean SIS 64 [ SD 32]) and 332 rehabilitation patients (mean age 65.7 [ SD 11] years, mean SIS 61 [ SD 11]), we derived an 8‐item SF ‐ SIS that demonstrated good agreement with original SIS and good correlation with our chosen functional and quality of life measures (all ρ>0.70, P <0.0001). Significant associations were seen with our chosen predictors of stroke outcome in the acute group ( P <0.0001). The focus group agreed with the choice of items for SF ‐ SIS across 7 of 8 domains . Conclusions Using multiple, complementary methods, we have derived an SF‐ SIS and demonstrated content, convergent, and discriminant validity. This shortened SIS should allow collection of robust quality of life data with less associated test burden.