Making the best match: selecting outcome measures for clinical trials and outcome studies.

Selecting an appropriate outcome measure is a critical step in designing valid and useful clinical trials and outcome studies. This selection process needs to extend beyond examining basic psychometric properties to consider additional features of instruments that may affect their validity and utility for the study's purpose. This article discusses these additional factors and their potential impact on outcome measurement. Guidelines are proposed to help clinical researchers and consumers of clinical research literature evaluate the match between the study purpose, population, and instrument.