Patient-reported outcome instrument selection: Designing a measurement strategy

Objective: To discuss issues in the design of a measurement strategy related to the use of patient-reported outcomes (PROs) in support of a labelling claim. Methods: In association with the release by the US Food and Drug Administration of its draft guidance on the use of PROs to support labeling claims, the Mayo/FDA Patient-Reported Outcomes Consensus Writing Group was formed. This paper, part of a series of manuscripts produced by the Writing Group, focuses on designing a PRO measurement strategy. Results: Developing a PRO measurement strategy begins with a clear statement about the proposed label claim that will derive from the PRO data. Investigators should identify the relevant domains to measure, develop a conceptual framework, identify alternative approaches for measuring the domains, and synthesize the information to design the measurement strategy. Often, there is not an already existing single instrument that has been developed and validated for the purposes of a given study. In such cases, investigators may consider supplementing an already existing questionnaire with additional scales or questions, modifying already existing instruments for a new application or patient population, or developing a new instrument altogether. The level of revalidation required for modifications and adaptations depends on the extent of the changes made. Revalidation requirements may range from cognitive testing/debriefing to confirm that subjects respond to the new instrument as expected to full-scale reliability and validity evaluations. Conclusion: A position of "reasonable pragmatism" is recommended such that the best available measurement strategy be considered as evidence for labeling.