Psychometric evaluation of the Stroke Impact Scale 3.0.

Background: 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 and 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 α 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.