Statistical challenges in drug approval trials that use patient-reported outcomes.

This article describes challenging aspects of the use of patient-reported outcome instruments in clinical trials for drug approval, in our perspective as statistical reviewers at the US Food and Drug Administration. We discuss aspects of planning and interpreting results in clinical trials (1) adapting an existing patient-reported outcome instrument for use in clinical trials, (2) using multi-item patient-reported outcomes and (3) missing patient-reported outcome values from many subjects over time. These challenges are illustrated with multiple examples from different clinical trials for different indications. We finally discuss important considerations in labeling.