Evidence-appraisal glossary
Negative Control Outcome
An outcome the exposure could not plausibly cause, examined to see whether a study's methods produce a spurious association anyway. If the exposure appears linked to something it cannot affect, hidden bias or confounding is probably at work.
Also called: negative control, control outcome.
A negative control acts like a smoke detector for bias. If a vaccine appears associated with an event that occurred before it was even given, that signal must come from confounding or selection rather than a genuine effect. Negative control outcomes, along with the parallel idea of negative control exposures, help reveal unmeasured confounding that ordinary adjustment cannot remove, and some methods use them to partially correct the estimate.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.