Structural validity of the foot and ankle outcome score for orthopaedic pathologies with Rasch Measurement Theory

Krista Tapaninaho; Antti J Saarinen; Outi Ilves; Mikko M Uimonen; Arja H Häkkinen; Henrik Sandelin; Jussi P Repo

doi:10.1016/j.fas.2021.03.005

Structural validity of the foot and ankle outcome score for orthopaedic pathologies with Rasch Measurement Theory

Foot Ankle Surg. 2022 Feb;28(2):193-199. doi: 10.1016/j.fas.2021.03.005. Epub 2021 Mar 16.

Authors

Krista Tapaninaho¹, Antti J Saarinen¹, Outi Ilves², Mikko M Uimonen¹, Arja H Häkkinen³, Henrik Sandelin⁴, Jussi P Repo⁵

Affiliations

¹ Department of Surgery, Central Finland Hospital District, Jyväskylä, Finland.
² Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland.
³ Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland; Department of Physical Medicine, Central Finland Healthcare District, Jyväskylä, Finland.
⁴ Department of Orthopaedics and Traumatology, Vaasa Central Hospital, Vaasa and University of Helsinki, Helsinki, Finland; Mehiläinen Sports Hospital, Vaasa, Finland; Department of Orthopaedics and Traumatology, Helsinki University Hospital, Helsinki, Finland.
⁵ Department of Orthopaedics and Traumatology, Tampere University Hospital, Tampere, Finland. Electronic address: mrjussirepo@gmail.com.

PMID: 33757731
DOI: 10.1016/j.fas.2021.03.005

Abstract

Background: The Foot and Ankle Outcome Score (FAOS) is one of the most frequently used patient-reported outcome measures for foot and ankle conditions. The aim is to test the structural validity of the Finnish version of the FAOS using Rasch Measurement Theory.

Methods: FAOS scores were obtained from 218 consecutive patients who received operative treatment for foot and ankle conditions. The FAOS data were fitted into the Rasch model and person separation index (PSI) calculated.

Results: All the five subscales provided good coverage and targeting. Three subscales presented unidimensional structure. Thirty-eight of the 42 items had ordered response category thresholds. Three of the 42 items had differential item functioning towards gender. All subscales showed sufficient fit to the Rasch model. PSI ranged from 0.73 to 0.94 for the subscales.

Conclusions: The Finnish version of the FAOS shows acceptable structural validity for assessing complaints in orthopaedic foot and ankle patients.

Keywords: Psychometric properties; Quality of life; Validity.

MeSH terms

Ankle* / surgery
Humans
Orthopedics*
Psychometrics / methods
Reproducibility of Results
Surveys and Questionnaires