Self-assessment of foot health: requirements, issues, practicalities, and challenges.

If self-referent instruments about people's health are to be useful in clinical and research settings, those instruments must be developed according to well-established processes and principles of measurement. We outline the main processes that should occur in the development of self-referent measuring instruments in general, with a focus, for illustrative purposes, on those intended to assess foot health. Requirements and issues concerning different forms of reliability and validity receive the most attention. In particular, problems associated with indices of test-retest reliability, inter-item homogeneity, and construct validity are identified and discussed. Practicalities concerning administration and scoring are also considered. A list of questions is provided for prospective users to assess the characteristics and quality of self-referent instruments.