A Core Outcome Set (COS) is a standardized set of domains and instruments that define the minimum outcomes to be measured and reported in all clinical trials related to a specific clinical area. It is developed through a rigorous consensus process involving diverse collaborators, including patient research partners, healthcare professionals, and researchers. The process has two key phases:
1. Identifying what to measure (domains), which results in a Core Domain Set.
2. Determining how to measure these domains through the selection of validated instruments.
By providing a common framework for measuring and reporting outcomes, a COS ensures consistency and comparability across studies, leading to more reliable and meaningful data in research on a particular health condition.