the degree to which a measurement instrument yields consistent results when administered to the same participants under similar conditions at different points in time. In other words, it assesses the stability of a measure. Within the OMERACT framework, it falls under the Discrimination pillar of the OMERACT Filter, which evaluates an instrument’s ability to distinguish between different states, groups, or time points.
Synonyms: Reproducibility
Example
A patient-reported questionnaire designed to measure fatigue in rheumatoid arthritis patients is completed by the same group of participants twice, two weeks apart, with no expected change in their fatigue levels. If the scores remain highly consistent between the two time points (e.g., ICC ≥ 0.80), the questionnaire demonstrates good test–retest reliability, meaning it reliably measures fatigue over time.