Review article: A primer for clinical researchers in the emergency department: Part VI. Measuring what matters: Core outcome sets in emergency medicine research.

In this series we address important topics for clinicians who participate in research as part of their work in the ED. The overarching goal of clinical research is to improve care and determine which treatment is best. Yet, defining and measuring outcomes - what is 'best' - can be one of the most difficult steps in the design of a study, in particular when answers to research questions cannot be captured in simple binary results. This article addresses how to choose outcome measures and highlights the increasingly important concept of core outcome sets.