Defining disabling foot pain in older adults: further examination of the Manchester Foot Pain and Disability Index.

OBJECTIVE

To identify a practical definition of disabling foot pain in older adults for clinical and research use, using the Manchester Foot Pain and Disability Index (FPDI).

METHODS

Adults aged > or =50 years registered with three general practices were mailed a two-stage cross-sectional survey. A total of 1342 respondents who reported foot pain in the previous 12 months and completed the FPDI and 58 participants in a test-retest repeatability study were included.

RESULTS

Confirmatory factor analysis verified the three-construct FPDI structure (pain intensity, functional limitation and appearance). Internal consistency for the three constructs was good (Cronbach's alpha 0.74, 0.92 and 0.77, respectively). A total of 1320 (98.4%) of those persons with foot pain reported disability (at least one of the 17 FPDI items experienced on at least some days -- Definition A). After restricting this definition to problems experienced on most/every day(s) (Definition B), 996 (74.2%) of those with foot pain reported disability (percentage difference 24.2%; 95% CI 21.9, 26.5%). For each of the three constructs, the prevalence of disability among persons with foot pain was significantly higher under Definition A than under Definition B. Test-retest repeatability for the individual constructs ranged from fair to substantial. Physical function, measured by the SF-36 physical function sub-scale, was poorer in those who reported problems within the function construct compared with those with problems in pain and/or appearance constructs only.

CONCLUSION

A practical definition of disabling foot pain [at least one of the 10 FPDI function items experienced on most/every day(s)] is proposed, which appears valid, repeatable and suitable for use in older adults.