title: Evaluation of the measurement properties of the Manchester foot pain and disability index.
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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: EMGO + Institute for health and care research, Department of general practice and elderly care medicine, VU University Medical Centre, Amsterdam, The Netherlands. b.vanderzwaard@vumc.nl.
authors.forename: Babette C
authors.initials: BC
authors.lastname: van der Zwaard
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Terwee
authors.forename: Edward
authors.initials: E
authors.lastname: Roddy
authors.forename: Berend
authors.initials: B
authors.lastname: Terluin
authors.forename: Henriette E
authors.initials: HE
authors.lastname: van der Horst
authors.forename: Petra J M
authors.initials: PJ
authors.lastname: Elders
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D003466:Cultural Characteristics; D004185:Disability Evaluation; D004739:England; D005163:Factor Analysis, Statistical; D005260:Female; D005528:Foot / Q000294:innervation*; D006801:Humans; D033183:Interdisciplinary Communication; D008297:Male; D008875:Middle Aged; D059352:Musculoskeletal Pain / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D009426:Netherlands; D010147:Pain Measurement; D058748:Pain Perception; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D014175:Translating