the essential, cross-cutting aspects of health and functioning that are relevant to almost all conditions or settings. They represent the core building blocks for evaluating outcomes and form a baseline for comparing interventions across different diseases. These domains capture fundamental concepts such as pain, fatigue, physical function, or quality of life that underpin patient experience regardless of diagnosis.
Example
Within OMERACT, foundational domains such as pain intensity, pain interference, fatigue, and physical function are considered in almost every core outcome set.