Background: The Manchester Foot Pain and Disability Index (MFPDI) has been used to determine the prevalence of disabling foot pain in several studies, however there is some debate as to which case definition is most appropriate. The objective of this study was to explore age and gender differences in the proportion of people with disabling foot pain using three different case definitions of the MFPDI and for each individual MFPDI item.
Methods: A random sample of 223 participants aged 27 to 90 years (88 males and 135 females) from the North West Adelaide Health Study, who reported having pain, aching or stiffness in either of their feet on most days in the last month, completed the MFPDI by telephone interview. The proportion of people with disabling foot pain was determined using three definitions: (i) Definition A-at least one of the 17 items documented on at least some days in the last month; (ii) Definition B-at least one of the 17 items documented on most/every day(s) in the last month, and; (iii) Definition C-at least one of the ten functional limitation items documented on most/every day(s) in the last month. Cross-tabulations and chi-squared statistics were used to explore differences in responses to the MFPDI items according to age and gender.
Results: The proportion of people with disabling foot pain according to each definition was as follows: Definition A (100%), Definition B (95.1%) and Definition C (77.6%). Definition C was most sensitive to age and gender differences. Exploration of individual MFPDI items indicated that age significantly affected both the pain intensity and functional limitation items, with younger people more likely to report their foot pain being worse in the morning, and older people more likely to report functional limitations. Although gender did not influence responses to the personal appearance items, women were more likely report functional limitations than men.
Conclusions: Definition C of the MFPDI is more sensitive to age and gender differences in the proportion of people with disabling foot pain, and would therefore seem to be the most appropriate case definition to use in epidemiological studies involving a broad age range of participants.