Rasch analysis of the Lower Extremity Functional Scale for foot and ankle patients.

ABSTRACT

Purpose: The Lower Extremity Functional Scale (LEFS) is a widely used 20-item patient-reported outcome instrument with five response categories. We investigated the measurement properties of the Finnish version of the LEFS among foot and ankle patients to refine the scale to measure more accurately what is relevant for patients.Materials and methods: Data were obtained from 182 patients who had undergone foot and ankle surgery for various reasons. The Rasch Measurement Theory and Cronbach's alpha were employed for analyses of model and item fit, response category thresholds, targeting, person separation index, and internal consistency.Results: Threshold misfit was noted in 13 of the 20 items. After collapsing the response categories 1 ("Quite a bit of difficulty") and 2 ("Moderate difficulty"), five items were removed one by one to make the scale fit the model. This new 15-item scale with four response categories had a unidimensional structure with good item fit, ordered thresholds, and good coverage/targeting. The person separation index and Cronbach's alpha were 0.85 and 0.95, respectively.Conclusions: This study provides a new 15-item LEFS with four response categories for clinicians and researchers to measure function in foot and ankle patients in a relevant way.Implications for rehabilitationAssessing foot and ankle function and rehabilitation effectiveness is of high importance.The Lower Extremity Functional Scale (LEFS) is a widely used 20-item patient-reported outcome instrument with five response categories.The Finnish LEFS was revised to better fit into the Rasch model.The new LEFS with 15 items and four response categories for foot and ankle patients is a psychometrically sound, meaningful, and operable instrument.