Evidence-appraisal glossary
Primary endpoint
The primary endpoint is the single main outcome a trial is designed and powered to measure, chosen in advance to answer its central question.
Also called: primary outcome, primary endpoint measure.
Because the sample size and the main statistical test are built around it, the primary endpoint is the result that carries the most weight when you judge whether a treatment worked. A trial should name one (or very few) primary endpoints in its protocol before enrollment. Be wary when a paper leads with a favorable secondary result while the pre-specified primary endpoint was neutral or negative, which can signal outcome switching.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.