Table 2 Definitions for aspects of domains and measurement properties from the COSMIN checklist by Mokkink et al. [27]

Validity: The degree to which an HR-PRO instrument measures the construct(s) it purports to measure

Content validity

The degree to which the content of an HR-PRO instrument is an adequate reflection of the construct to be measured

 Face validity^a

The degree to which an HR-PRO instrument indeed looks as though they are an adequate reflection of the construct to be measured

Construct validity

The degree to which the scores of an HR-PRO instrument are consistent with hypotheses based on the assumption that a HR-PRO instrument validly measures the construct to be measured

 Structural validity^b

The degree to which the scores of an HR-PRO instrument are an adequate reflection of the dimensionality of the construct to be measured

Hypothesis testing^b

Item construct validity

Criterion validity

The degree to which the scores of an instrument satisfactorily reflect a “gold standard”

Responsiveness

Responsiveness: the capability of an HR-PRO instrument to detect change in the construct to be measured over time

Interpretability^c

Interpretability: the extent to which qualitative meaning is reflective of an instrument’s quantitative scores or score change

Reliability: The degree to which the measurement is free from measurement error

Internal consistency

The degree of the interrelatedness among the items

Reliability

The proportion of total variance in the measurements due to “true” differences amongst patients

Measurement error

The systematic and random error of a patient’s score that is not attributed to true changes in the construct to be measured