Glossary Term
Longitudinal construct validity
An OMERACT measurement property that assesses an instrument’s ability to accurately detect change over time when change in the construct of interest is expected to have occurred. It is sometimes referred to as responsiveness.
Longitudinal construct validity is evaluated by testing a priori hypotheses about the expected direction and magnitude of change, or about expected relationships between change scores on the instrument and change measured by other relevant instruments or indicators. Evidence across several situations of change builds confidence that the instrument can accurately measure change.
Relationship to Construct Validity: Construct validity assesses whether an instrument’s scores behave as expected at a given point in time. Longitudinal construct validity applies the same hypothesis-testing approach to change scores over time, asking whether observed changes behave as expected when the underlying construct changes.
Examples
Before assessing an instrument measuring physical function in patients undergoing joint replacement, researchers hypothesize that physical function will improve substantially following surgery. If the instrument detects a large improvement of the expected magnitude, and its change scores correspond with changes on other relevant measures or indicators of improvement, this provides evidence supporting longitudinal construct validity.