Background: The Manchester Foot Pain and Disability Index (MFPDI) is a self-assessment questionnaire developed in
the UK to measure foot pain and disability in the general population1. It has been translated and validated in several
languages 2,3
Objectives: The aim of this study was to conduct cross-cultural adaptation and validation of the MFPDI into Spanish
Methods: The cross-cultural adaptation process was undertaken using International Society for Pharmacoeconomics
and Outcomes Research (ISPOR)4 recommendations. This involved 8 stages: i) Forward translation, ii) Reconciliation,
iii) Back translation, iv) Back translation review, v) Harmonisation, vi) Pilot, vii) Pilot review, and viii) Proofreading. In the
validation phase, the MFPDI datasets from the UK (original) and Spain (adapted) were pooled and subjected to Rasch
analysis. Fit to the Rasch model, unidimensionality, reliability and cross-cultural invariance is reported
Results: The pooled dataset comprised 1015 patients (Spain n=333 and UK n=682) with characteristics summarised in
Table 1. Rasch analysis confirmed three subscales for both the Spanish and UK datasets and fit to the Rasch model X2
(df) = 15.945 (12), p = 0.194 and 31.024 (21), p = 0.073, for Spain and UK . The reliability (Person Separation Index -
PSI) was .85 and .82 for Spain and UK respectively. Significant cross-cultural non-invariance was present on the
Functional and Personal appearance subscales. Adjustment for the bias was achieved by ‘splitting’ the affected
subscales and creation of cultural-specific subscales for each country and cultural-general subscale. Fit to the Rasch
model was satisfied following cross-cultural adjustment (Table 1). The MFPDI was calibrated into interval-level scales for
Spain and UK to enable future data pooling or comparisons.
Sampl
e
size
Gender Age Item Fit
Residual
Person Fit
Residual
Chi Square
Interaction
PSI
Analysis N Female
(%)
Mean
(SD)
Mean SD Mean SD Value
(df)
p
Spain 333 248
(74.4)
51.6
(15.2)
-0.164 3.07 -
0.364
0.93 15.95
(12)
0.19 0.85
UK 682 416
(61.0)
55.2
(16.7)
-0.366 2.80 -
0.429
0.99 31.02
(21)
0.07 0.82
Pooled 1015 663
(65.4)
52.8
(15.8)
-0.766 4.40 -
0.441
1.06 49.17
(27)
0.01 0.84
DIFAdjusted
-0.420 2.98 -
0.415
0.98 57.94
(45)
0.09 0.84
Table 1: P = Χ2 interaction probability, (non-significant P = Fit to the model), PSI = Person separation index
Conclusions: A gold standard translation process (ISPOR) has been used to develop a Spanish (for Spain) version of
the MFPDI, a widely used foot-specific patient-reported outcome measure. Rasch analysis has confirmed that the MFPDI
is a robust 3-subscale measure of foot pain, function and appearance in both its English and Spanish versions. Future
work can make cross-cultural comparisons using the calibrated scales
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