Psychometric Evaluation of the Stroke Impact Scale 3.0

Ercole Vellone, Serenella Savini, Roberta Fida, Victoria Vaughan Dickson, Gail D'Eramo Melkus, Francisco Javier Carod-Artal, Gennaro Rocco, Rosaria Alvaro
2015 Journal of Cardiovascular Nursing  
The Stroke Impact Scale 3.0 (SIS 3.0) is widely used to measure quality of life in stroke survivors; however, previous studies have not tested the original 8-factor structure of the scale. In addition, previous studies have shown floor and ceiling effect and weak reliability within the scale. Objective: The aim of this study was to evaluate the psychometric characteristics of the SIS 3.0, including its construct validity (factorial structure, concurrent and contrasting group validity), floor
more » ... ceiling effect, and reliability. Method: A cross-sectional design was used to study 392 stroke survivors enrolled in 16 rehabilitation facilities across Italy. Factorial structure of the SIS 3.0 was tested with confirmatory factor analysis. Concurrent and contrasting group validities were evaluated with other scales measuring functional capacities, neurological functions, cognition, anxiety, depression, and generic quality of life. Floor and ceiling effects were evaluated by determining the percentages of patients with the minimum and the maximum score at SIS 3.0. Reliability was determined by Cronbach's ! and test-retest. Results: Participants were 71 years old on average (SD, 11 years); 55% were men. Confirmatory factor analysis revealed a new 4-factor structure that fitted the data better than the original 8-factor structure did. Concurrent and contrasting group validity of the new 4-factor structure was supportive and no floor and ceiling effects were found. Internal consistency and test-retest reliability ranged between 0.79 and 0.98. Conclusion: The new factorial structure of the SIS 3.0 with 4 factors showed better psychometric properties than the original 8-factor structure did. This evidence supports further use of the SIS 3.0 in clinical practice and research. KEY WORDS: instrument validity and reliability, psychometrics, stroke survivors 1 Ercole Vellone, RN, MSN These instruments assess only a few areas compromised by stroke and do not provide a comprehensive and specific assessment of stroke survivors' QOL. In the last 2 decades, specific instruments have been developed to measure QOL in stroke survivors, the Stroke Impact Scale (SIS), 10,11 the Stroke-Specific Quality of Life Scale, 12 and the Stroke and Aphasia QOL Scale, 13 that are more sensitive to short-term changes in the health status of stroke survivors than generic QOL tools are. The SIS 2.0 was developed in the United States and first published in 1999 10 as a 64-item multidimensional instrument to measure QOL in stroke survivors. The instrument has no theoretical underpinning, but the development process followed a rigorous qualitative and quantitative procedure where patients, informal caregivers, and experts in stroke were involved. 14 Developers conducted several focus groups and expert panels to identify impairments, disabilities, and handicaps determined by stroke. After this process, the following 8 dimensions of the impact of stroke were identified: Strength, Hand function, Activities of daily living (ADL)/Instrumental activities of daily living (IADL), Mobility, Physical functioning, Memory, Communication, Emotion, and Social participation. In addition, the SIS 2.0 included a 100-mm visual analog scale to measure global recovery after stroke with a separate score. The above 8-dimension structure of the SIS 2.0 was never empirically tested. Duncan et al 10 reported an exploratory factory analysis where 5 factors were found, which evidently do not correspond to the 8 dimensions. Initially, the tool was tested for contrasting group validity (being able to discriminate groups of stroke survivors with different level of disability) and concurrent validity. 10 Internal consistency reliability was adequate (ranging between 0.83 and 0.90), but test-retest reliability for the Emotional dimension was only 0.57. The authors commented that, probably, the low reliability was a result of an item with bad item-domain correlation and to a "random variability" of all items included in this domain. In the same study analysis, the SIS 2.0 showed a floor effect in the Hand function domain (40.2% of the sample who scored 0) and a ceiling effect in the Communication domain (35.4% of the sample who scored 100) and the Social participation domain (15.6% of the sample who scored 100). Edwards and O'Connell 15 tested the SIS 2.0 in Australia. Validity was tested by item-domain correlations, which were all greater than 0.40, and correlating the SIS 2.0 with the Zung Self-rating Depression Scale and the WHOQOL-Brief Scale. The correlations with the first scale, with the exception of the Strength domain, were all significant, with coefficients ranging
doi:10.1097/jcn.0000000000000145 pmid:24695074 fatcat:lhl4zewwx5gmlpuz3mmoyjppki