Construct validity, responsiveness, minimal detectable change, and minimal clinically important difference of the stroke self-efficacy questionnaire in individuals receiving stroke rehabilitation

Abstract

Purpose To assess the clinimetric properties of the Stroke Self-Efficacy Questionnaire (SSEQ) and estimate the minimal detectable change (MDC) and minimal clinically important difference (MCID) from the database of our randomized controlled trials (RCT) of individuals receiving stroke rehabilitation. Methods We retrieved the pre- and post-intervention scores of the SSEQ and Stroke Impact Scale (SIS) from 80 stroke survivors. The analysis of clinimetric properties was performed using: (1) confirmatory factor analysis and item response theory modeling (IRT) for construct validity; (2) standardized response mean and Glass’s delta for responsiveness; (3) MDC based on the standard deviation (SD) or standard error of measurement (SEM) of the SSEQ change scores; (4) MCID determined by the external anchor–SIS; (5) conditional MDC (cMDC) derived from the IRT analysis. Results There was a bi-factorial construct with excellent model-data fit and marked responsiveness. The MDC determined by the SD and SEM were 1.5 and 3.0, respectively, and the MCIDs were 3.3 and 3.7. Conclusions This study confirmed that SSEQ is a valid and reliable assessment tool for patients receiving stroke rehabilitation. We also provided practical threshold values, especially demonstrating the benefit of using individualized cMDC, to help clinicians better interpret the change in the SSEQ scores.