Publishing nutrition research: validity, reliability, and diagnostic test assessment in nutrition-related research.

This is the sixth in a series of monographs on research design and analysis. The purpose of this article is to describe and discuss several concepts related to the measurement of nutrition-related characteristics and outcomes, including validity, reliability, and diagnostic tests. The article reviews the methodologic issues related to capturing the various aspects of a given nutrition measure's reliability, including test-retest, inter-item, and interobserver or inter-rater reliability. Similarly, it covers content validity, indicators of absolute vs relative validity, and internal vs external validity. With respect to diagnostic assessment, the article summarizes the concepts of sensitivity and specificity. The hope is that dietetics practitioners will be able to both use high-quality measures of nutrition concepts in their research and recognize these measures in research completed by others.