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Foot Ankle Surg. 2019 Dec 4. pii: S1268-7731(19)30200-0. doi: 10.1016/j.fas.2019.11.002. [Epub ahead of print]

Validating the Foot and Ankle Outcome score for measuring foot dysfunction among hallux valgus surgery patients using item response theory.

Author information

1
School of Population and Public Health, University of British Columbia, Vancouver, Canada. Electronic address: fardowsay@live.com.
2
Centre for Health Services and Policy Research, School of Population and Public Health, University of British Columbia, Vancouver, Canada. Electronic address: guiping.liu@ubc.ca.
3
Department of Orthopaedics, University of British Columbia, 181 Keefer Place, Unit 221, Vancouver, Canada. Electronic address: KWing@footbridgeclinic.com.
4
Department of Surgery, University of Calgary, Calgary, Alberta, Canada. Electronic address: tcrump@ucalgary.ca.
5
Department of Orthopaedics, University of British Columbia, 181 Keefer Place, Unit 221, Vancouver, Canada. Electronic address: murray.penner@gmail.com.
6
Department of Orthopaedics, University of British Columbia, 181 Keefer Place, Unit 221, Vancouver, Canada. Electronic address: alastair.stephen.younger@gmail.com.
7
Department of Orthopaedics, University of British Columbia, 181 Keefer Place, Unit 221, Vancouver, Canada. Electronic address: docveljkovic@yahoo.com.
8
Centre for Health Services and Policy Research, School of Population and Public Health, University of British Columbia, Vancouver, Canada. Electronic address: jason.sutherland@ubc.ca.

Abstract

BACKGROUND:

There is an absence of high quality research validating instruments that measure foot and ankle related quality of life among hallux valgus (bunion) patients' perspectives. The Foot and Ankle Outcome Scale is a patient-reported outcome instrument, that when administered to patients with symptomatic hallux valgus, provides a patient-centric perspective of their foot function. The aim of this study is to assess the psychometric properties of the instrument's five subscales among preoperative bunion surgery patients.

METHODS:

The Foot and Ankle Outcome Scale instrument measures Pain, Symptoms, Activities of Daily Living, Sport and Recreational Activities and Foot/Ankle Related Quality of Life. Preoperative data is collected from a sample of patients scheduled for surgical treatment of their condition in Vancouver, Canada. Classical and item response theory methods are used to report on reliability, validity and differential item functioning among subgroups.

RESULTS:

This study included 249 surveys, representing an overall response rate of 44.1% among 564 eligible patients. The instrument demonstrated high reliability for all subscales, though 18 items across subscales, exhibited poor discrimination between item levels. Four items score differently according to patients' sex and one item scored differently by age.

CONCLUSIONS:

The instrument measures five domains of health important to bunion patients. These findings suggest that the current instrument can be used with an understanding of its limitations, including redundant questions and sex-based differences. Future research should revise a number of items. The results highlight the importance of the psychometric analyses of instruments in specific patient populations.

KEYWORDS:

Bunion surgery; Foot and Ankle Outcome scale; Outcomes; Quality of life

PMID:
31839477
DOI:
10.1016/j.fas.2019.11.002

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