Table 1.

Definitions for key measurement properties used in evaluating the quality of patient reported outcomes instruments.

Measurement Property	Definition
Content Validity	The degree to which the content of an instrument is an adequate reflection of the construct to be measured
Criterion Validity	Strength of relationship between questionnaire scores and a measurable external criterion (the “gold standard”)
Construct Validity	The degree to which the scores of a questionnaire are consistent with the theoretical construct (hypothesis) that is being measured
Face Validity	The degree to which items in an instrument look as though they are an adequate reflection of the construct being measured
Internal Consistency	The extent to which the items are interrelated, and thus measure the same construct
Reliability	The extent to which patients can be distinguished from each other despite measurement errors
Test-Retest Reliability	The extent to which scores for patients who have not changed are the same in repeated measurements over time
Interrater Reliability	The extent to which scores for patients who have not changed are the same over repeated measurements by different examiners during the same visit
Responsiveness	The ability to detect clinically meaningful change over time in the construct being measured
Interpretability	The degree to which quantitative scores can be given qualitative meaning. Identifying clinically important differences in results.
Cross-Cultural Equivalence	The same measurement instrument used in different cultures measures the same construct without additional external cultural influences on results