Understanding clinical trial outcomes: design, analysis, and interpretation.

Outcomes (a variable intended for comparison between groups) are integral to the design, conduct, and data analysis of a clinical trial. They are broadly divided into four categories: physician based, patient reported, economic based, and technology based. Each is used in dermatology to some degree, but no consensus exists as to what type of outcome or degree of validation should be employed. This is problematical because poor quality outcomes or their incorrect use may invalidate the results of a clinical trial. Despite their importance, outcome measures in dermatology receive little attention. The present authors aim to provide an overview of important considerations for outcome measures and a practical approach to their analysis.