Issues in measuring change in self-perceived oral health status.

An important goal of a health care intervention or system is to improve the health of an individual or a population. The challenge for health services research is to measure and explain this change. However, the issue of how changes in health status should be defined and measured has been given relatively little attention. This paper draws on the rather sparse literature to examine some issues involved in measuring changes in oral health status and illustrates these using data from a longitudinal study of the oral health of older adults. The paper draws a distinction between quantitative and qualitative change and the challenges involved with each. Four different ways of assessing change are reviewed and their strengths and weaknesses highlighted. Global transition judgements, although relatively simple measures of change, incorporate patients' values and avoid the statistical problems associated with measures such as change scores. Nevertheless, the measurement of change in oral health status is complex and controversial and no approach is universally accepted. Consequently, the decision as to which strategy to adopt is far from simple.