Table 1 Definitions of Important Measurement Properties: Comparison of the COSMIN Taxonomy and Definitions and Quality Criteria for Measurement Properties Definitions [7,8,9]

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

The extent to which the domain of interest is comprehensively sampled by the items in the questionnaire

The degree of the interrelatedness among the items

The extent to which items in a (sub)scale are intercorrelated, thus measuring the same construct

The degree to which the scores of an HR-PRO instrument are an adequate reflection of a ‘gold standard’

The extent to which scores on a particular questionnaire relate to a gold standard

The degree to which the scores of an HR-PRO instrument are consistent with hypotheses (for instance with regard to internal relationships, relationships to scores of other instruments, or differences between relevant groups) based on the assumption that the HRPRO instrument validly measures the construct to be measured

The extent to which scores on a particular questionnaire relate to other measures in a manner that is consistent with theoretically derived hypotheses concerning the concepts that are being measured

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

Item construct validity

The degree to which the performance of the items on a translated or culturally adapted HR-PRO instrument are an adequate reflection of the performance of the items of the original version of the HR-PRO instrument

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

The extent to which the scores on repeated measures are close to each other (absolute measurement error)

The proportion of the total variance in the measurements which is due to ‘true’† differences between patients

The extent to which patients can be distinguished from each other, despite measurement errors (relative measurement error)

The ability of an HR-PRO instrument to detect change over time in the construct to be measured

The ability of a questionnaire to detect clinically important changes over time

(Not Defined)

The number of respondents who achieved the lowest or highest possible score

Interpretability is the degree to which one can assign qualitative meaning - that is, clinical or commonly understood connotations – to an instrument’s quantitative scores or change in scores.

The degree to which one can assign qualitative meaning to quantitative scores