Content Validation by Patients and Experts: Is the PRO Measure Fit for Purpose?

The use of a PRO measure assumes a link between the content in a measure and the targeted underlying construct (Wynd et al. 2003). In addition to other types of data, this is fundamentally demonstrated by evidence of content validity, i.e. the ‘complete relevance’ of the content to the target population and how adequately it represents the underlying construct. Without such evidence, the definition of the underlying concept being measured becomes ambiguous, and the scores would be rendered meaningless (Haynes et al. 1995). While evidence ensuring content validity is generated through inclusion of input from patients in defining the content of the measure, confirming that ‘complete relevance’ has been attained is crucial. This is addressed in Steps IV and V of the roadmap, where respondent understanding of the measure and comprehensives is explicitly explored in Step IV, with practicality and acceptability explored in Step V. Importantly, both steps allow the PRO measure to be fine-tuned to address any issues uncovered in the steps. These steps are illustrated in the current chapter, based on the patient and clinician panels conducted to assess the content validity of the HidroQoL as well as a pilot test of the measure assessing the practicality and acceptability of the HidroQoL.