Measurement properties of the Falls Efficacy Scale-International (FES-I) in persons with late effects of polio: A cross-sectional study

Background: Fear of falling (FoF) is very common in persons with late effects of polio (LEoP). An internationally recognized rating scale to assess FoF is the Falls Efficacy Scale-International (FES-I). Yet, there is limited knowledge about its measurement properties in persons with LEoP.

Objective: To investigate the measurement properties of FES-I (16-item version) and short FES-I (7-item version) in persons with LEoP.

Design: Explorative factor analysis and Rasch model analysis of cross-sectional data.

Setting: University Hospital.

Participants: A total of 321 persons with LEoP (mean age 70 ± 10 years, 173 women).

Main outcome measurement: The FES-I and short FES-I, comprising four response options about concerns of falling ranging from 1 (not at all concerned) to 4 (very concerned).

Methods: Data were collected by a postal survey. First, a factor analysis was performed to investigate unidimensionality of the scale. Thereafter, a Rasch model analysis was used to further analyze the measurement properties of FES-I and short FES-I, such as local dependency, targeting, hierarchical order of items, Differential Item Functioning (DIF), response category functioning and reliability (Person Separation Index, PSI). Raw score transformation to interval measurements was also performed.

Results: The factor analysis revealed that FES-I was unidimensional, even though the Rasch analysis showed some misfit to the Rasch model and local dependency. Targeting for FES-I and short FES-I was somewhat suboptimal as the participants on average reported less FoF than expected. A negligible gender DIF was found for two items in FES-I and for one item in short FES-I. Reliability was high (PSI >0.86), and the response category thresholds worked as intended for both FES-I, and short FES-I.

Conclusion: The FES-I and the short FES-I have sufficient measurement properties in persons with LEoP. Both versions can be used to assess fear of falling in this population. This article is protected by copyright. All rights reserved.