Research in primary dental care part 4: measures.

An important part of the design process for any study is deciding how to assess and measure the phenomena you are aiming to research. In this article we will use the term outcome measure to indicate the tool or index that can be used to quantify, in an accurate and predictable way, the phenomenon under investigation. This might, for example, be a patient's opinion, the effect of a treatment, the outcome of an intervention, or the prevalence of an oral disease. The paper presents an overview of outcome measures which can be used in research. We will discuss the properties to look for in a measure, suggest suitable evidence-based measures and briefly introduce how to go about developing new measures, in particular, questionnaires.