Self- and Proxy-Report Agreement on the Stroke Impact Scale

Abstract

Background and Purpose— The purpose of this study was to examine proxy-patient agreement on the domains of the Stroke Impact Scale (SIS), as per the proxy-proxy perspective. Methods— Stroke patients were prospectively assessed by means of the NIH Stroke Scale, Barthel index, and modified Rankin scale. Proxies and patients answered the Hospital Anxiety and Depression Scale and the SIS 3.0. Comparisons of patient-proxy mean scores (paired t test), effect size, and intraclass correlation coefficients (ICC) were calculated for each of the SIS domains, and weighted kappa for individual items. Results— 180 proxy-patient pairs were assessed. Proxies were younger (mean age: 43.1 versus 57.9 years) and had a higher education level ( P <0.0001). The bias between patient-proxy mean differences was low (from 5.3, Strength, to 0.1, Communication). Proxies significantly scored patients as more severally affected in Strength (41.7 versus 36.6; P <0.0001) and ADL (46.2 versus 43.1; P =0.01) domains, and Composite Physical Domain (CPD; 39.7 versus 34.9; P <0.0001). The magnitude of difference was small (size effect: 0.21). ICC values for the SIS domains ranged from 0.17 (Emotion) to 0.79 (Hand function). The ICC value for the CPD was 0.83. Memory, Communication, Emotion, and Social Participation domains had ICC lower values. The weighted kappa values for the SIS items ranged from 0.09 (item 4e) to 0.80 (item 7d). Highest values (moderate/high agreement) were observed for the SIS-16 and CPD (kappa values: 0.31 to 0.80). Conclusions— Agreement between stroke patients and proxies was acceptable for most SIS domains and SIS-16. Proxy’s assessment of SIS subjective domains should be taken with caution.