Outcomes in Clinical Trials

Selecting outcomes for clinical trials requires a wide range of considerations relating to clinical interpretation, ethics relating to therapy effectiveness and safety, and statistical optimality of measures. Appropriate outcome choice plays a key role in determining the usefulness and/or success of a study and can affect whether a proposed study is view favorably by funding and regulatory agencies. Many regulatory and funding agencies provide guidance on the types of outcomes that are appropriate or acceptable in various contexts, and it is important to understand regulatory guidelines, definitions, and expectations when choosing clinical outcomes. This chapter provides an overview of the clinical, practical, and statistical considerations in choosing outcomes, with a focus on the intersection between the considerations themselves and the standards and definitions provided by regulatory and funding agencies. Section “Introduction, Definitions, and General Considerations” introduces basic definitions and broad considerations in clinical trials outcomes. Section “Types of Outcome Measures” discusses clinical distinctions between outcomes, mathematical descriptions of outcomes, and safety considerations. Section “Choosing Outcome Measures” discusses both statistical and practical considerations in outcome choice, introduces approaches for evaluating the quality of selected outcomes, and makes distinctions in reporting outcomes. Section “Multiple Outcomes” examines the intricacies involved in using multiple outcomes, specifically multiple outcomes consisting of different, but possibly related, measures, and longitudinal studies that measure the same outcome for multiple times.