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Open Access Research article

Evaluation of the measurement properties of the Manchester foot pain and disability index

Babette C van der Zwaard1*, Caroline B Terwee2, Edward Roddy3, Berend Terluin1, Henriette E van der Horst1 and Petra JM Elders1

Author Affiliations

1 EMGO + Institute for health and care research, Department of general practice and elderly care medicine, VU University Medical Centre, Amsterdam, The Netherlands

2 EMGO + Institute for health and care research, Department of Epidemiology and Biostatistics, VU University Medical Centre, Amsterdam, The Netherlands

3 Research Institute for Primary Care and Health Sciences, Keele University, Staffordshire, UK

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BMC Musculoskeletal Disorders 2014, 15:276  doi:10.1186/1471-2474-15-276

Published: 12 August 2014

Abstract

Background

The Manchester Foot Pain and Disability Index (MFPDI, 19 items) was developed to measure functional limitations, pain and appearance for patients with foot pain and is frequently used in both observational studies and randomised controlled trials. A Dutch version of the MFPDI was developed. The aims of this study were to evaluate all the measurement properties for the Dutch version of the MFPDI and to evaluate comparability to the original version.

Method

The MFPDI was translated into Dutch using a forward/backward translation process. The dimensionality was evaluated using exploratory and confirmatory factor analysis. Measurement properties were evaluated per subscale according to the COSMIN taxonomy consisting of: reliability (internal consistency, test-retest reliability and measurement error), validity (structural validity, content validity and cross-cultural validity comparing the Dutch version to the English version) responsiveness and interpretation.

Results

The questionnaire consists of three scales, measuring foot function, foot pain and perception. The reliability of the foot function scale is acceptable (Cronbach’s α > 0.7, ICC = 0.7, SEM = 2.2 on 0-18 scale). The construct validity of the function and pain scale was confirmed and only the pain scale contains one item with differential item functioning (DIF). The responsiveness of the function and pain scale is moderate when compared to anchor questions.

Conclusion

Results using the Dutch MFPDI version can be compared to results using the original version. The foot function sub-scale (items 1-9) is a reliable and valid sub-scale. This study indicates that the use of the MFPDI as a longitudinal instrument might be problematic for measuring change in musculoskeletal foot pain due to moderate responsiveness.