an evidence-based conceptual framework and process used to guide the development and appraisal of core outcome measurement sets (Core Outcome Sets). It helps working groups decide what to measure (selecting appropriate domains) and how to measure them (selecting instruments).
At its core, the Filter requires every outcome measurement instrument—whether a questionnaire, scale, or other tool—to be evaluated across three clinimetric pillars:
Truth – Does the instrument measure the intended concept (face, content, construct, and criterion validity)?
Discrimination – Can it reliably distinguish between groups, across time, and in situations of interest (reliability and sensitivity to change)?
Feasibility – Can it be applied practically in research and clinical settings (burden, cost, time, and interpretability)?
If an instrument passes all three pillars, it is considered valid for use in OMERACT-endorsed Core Outcome Sets.
Revisions over time (Filter 2.0 in 2014, Filter 2.1 in 2019, and proposed refinements in Filter 2.2 in 2021) expanded the framework to include additional core areas (such as Death, Life Impact, Pathophysiological Manifestations, and Resource Use), clarified definitions, and improved decision-making processes for working groups.
Abbreviation: TDF
Example
A working group developing a core outcome set for psoriatic arthritis uses the OMERACT Filter to evaluate a fatigue questionnaire. They review evidence for Truth (does it truly measure fatigue?), Discrimination (does it detect meaningful changes over time and between treatment groups?), and Feasibility (is it short, low-cost, and easy for patients to complete?). Based on this evaluation, the group determines whether to include the questionnaire in the final Core Outcome Set.