Attributes of the MFPDI include:

Valid

The MFPDI has been repeatedly shown to demonstrate content, construct and criterion validity amongst people with varying levels of foot problems.

Reliable

The MFPDI exhibits good internal consistency.

Sensitive

The MFPDI has demonstrated its ability to discriminate between known groups with varying levels of a foot specific disability within both clinical and population settings.

Ease of use

The MFPDI is quick and easy to complete, administer and score.

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• van der Zwaard BC, Elders PJ, Knol DL, Gorter KJ, Peeraer L, van der Windt DA, van der Horst HE. Treatment of forefoot problems in older people: study protocol for a randomised clinical trial comparing podiatric treatment to standardised shoe advice. J Foot Ankle Res. 2011 Mar 31;4(1):11.
• Roddy E, Muller S, Thomas E. Onset and persistence of disabling foot pain in community-dwelling older adults over a 3-year period: a prospective cohort study. J Gerontol A Biol Sci Med Sci. 2011 Apr;66(4):474-80. Epub 2010 Nov 24.

• Menz HB, Roddy E, Thomas E, Croft PR. Impact of hallux valgus severity on general and foot-specific health-related quality of life. Arthritis Care Res (Hoboken). 2010 Nov 15.

• Mickle KJ, Munro BJ, Lord SR, Menz HB, Steele JR. Foot pain, plantar pressures, and falls in older people: a prospective study. J Am Geriatr Soc. 2010 Oct;58(10):1936-40.

• Menz HB, Tiedemann A, Kwan MM, Plumb K, Lord SR. Foot pain in community-dwelling older people: an evaluation of the Manchester Foot Pain and Disability Index. Rheumatology (Oxford). 2006 Jul;45(7):863-7. Epub 2006 Jan 31.

• Bowen CJ, Edwards CJ, Hooper L, Dewbury K, Sampson M, Sawyer S, Burridge J, Arden NK. Improvement in symptoms and signs in the forefoot of patients with rheumatoid arthritis treated with anti-TNF therapy. J Foot Ankle Res. 2010 Jun 17;3:10.

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The MFPDI was developed using a mixed method design incorporating a number of stages consistent with best practice:

Phase 1: Incorporating the patient’s perspective in order to understand the domain under investigation (Content validity)

Item generation

Interviews were conducted with 32 patients attending foot clinics for treatment to explore aspects of pain, disability, activity limitation and footwear. Statements were generated relating to foot problems and refined to form 19 items.

Pre-testing

Eleven patients attending podiatry clinics were asked to complete the first draft of the 19 item questionnaire. Changes to the questionnaire included; ensuring participants focused on disability relating to foot pain and not pain relating to general health, adding a response option in case an item was not personally relevant to the patient and adding a mechanism to reduce missing data.

Phase 2: Questionnaire pilot

The questionnaire was piloted to confirm acceptability among 100 general practice patients. Patients appeared to accurately complete and understand the questionnaire (particularly amongst the older age group).

Phase 3: Establishing validity and reliability

Factor analysis confirmed the presence of three domains within the MFPDI – (functional limitation, pain intensity and personal appearance). More recent research has shown two of the three constructs (functional limitation and pain) conform to Rasch measurement principles indicating the presence of unidimensional, equal interval scales.

Construct validity

The MFPDI was tested to ensure its ability to discriminate between groups expected to have different levels of foot disability. Three participant groups were included during this phase:

• Patients (45) attending rheumatology clinic, but not specifically for foot problem
• Patients (33) attending their general practitioner with foot complaint
• Patients (1000) on a GP register asked to take part in a general population survey if they had experienced pain in their foot for a whole day in last month.

Patients reporting pain or having marked at least one item positively were invited to take part in a standardised interview and examination. Test scores found greatest pain/disability among rheumatology patients and least pain/disability among community subjects.

Criterion validity

To test the MFPDIs ability to correlate with an established disability instrument, patients were asked to complete a sub scale of the Functional Limitation Profile questionnaire. Responses confirmed agreement between MFPDI scores and similar items on the Functional Limitation Profile.

Reliability

Internal consistency was confirmed using Cronbachs alpha (0.99) and Item total correlation values between 0.25 and 0.62.

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Individual scores for each construct can be generated to produce an overall index of foot disability.

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The MFPDI is to date validated for pen and paper completion. Careful migration to a digital delivery format (for example screen based device) can be authorised. Please contact us for advice.

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