In the OMERACT framework, Discrimination refers to an outcome measure’s ability to distinguish between situations of interest. This includes detecting differences:

1. Between groups (e.g., treatment vs. control/placebo groups).
2. Over time (e.g., responsiveness to change within individuals).
3. Within individuals (e.g., change in a single patient’s status).

It encompasses reliability (consistency across raters or occasions), sensitivity to change (responsiveness), and thresholds of meaning (the smallest change that is clinically important).