Table 1.

National Institutes of Health–recommended definitions of outcome measures[26]

Outcome	Definition
Clinical end point	"A characteristic or variable that reflects how a patient feels, functions, or survives."
Surrogate end point	"A biomarker that is intended to substitute for a clinical end point. A surrogate end point is expected to predict clinical benefit (or harm or lack of benefit or harm) based on epidemiologic, therapeutic, pathophysiologic, or other scientific evidence."
Biological marker (biomarker)	"A characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention."