Sickness Impact Profile: the state of the art of a generic functional status measure.

The Sickness Impact Profile (SIP) is a widely used health status measure, known to be valid and reliable. After the final development and testing in 1978, however, in which several methodological aspects were investigated, no descriptions of research projects that systematically evaluate the methodological and theoretical aspects of the instrument were found. In this article a review is presented of literature on the SIP. This review is the first step taken in a project that evaluates the SIP. The instrument appears to be a reliable instrument with sufficient content validity. It shows good correlations with other health status and functional status measures. Yet a number of questions about the SIP remain unanswered. Theoretical implications of the construct of sickness, the effect of age and gender on SIP scores, the construct validity judged by factor analysis, the responsiveness of the instrument, and the possibilities to use proxy-respondents or to shorten the list and to simplify the scoring procedure still have to be studied. If the instrument is to be used as an international standard measure of functional status, these topics should be thoroughly examined.