Designing prevalence and incidence studies.

Frequency, impact, and causes of diseases--including wound development--can be examined using prevalence and incidence studies. Understanding basic epidemiologic principles is necessary to avoid misinterpretation of the data and incorrect translation of the results into clinical practice. Definitions and examples of prevalence, cumulative incidence, incidence rate, confidence intervals, and sample size are given. They will help practitioners comprehend these concepts and critically evaluate published research.