outcome
Meaning of outcome: Choosing which result to measure decides what a study is able to claim, which is why the choice is fixed before anyone is enrolled.
Definition of outcome
An outcome is a specific, measurable result used to judge the effect of a disease, a treatment or any other intervention. Defining it in advance gives clinicians and researchers a fixed yardstick, so one approach can be compared against another or against no treatment at all. Survival, tumor size, laboratory values, symptom scores and reported quality of life all serve as outcomes.
Why is one outcome named in advance?
Because a study that measures twenty things will find something that looks good in at least one of them by chance alone. Naming a single primary outcome before enrollment begins commits the researchers to the question they set out to answer, and everything else is reported as secondary. The primary outcome also determines how many participants are needed, since detecting a small difference in survival takes far more people than detecting a change in a blood test. Reporting a secondary result as though it had been the point is a recognized way of making a disappointing study look successful, which is why the plan is registered publicly beforehand.
What kinds are used?
| Kind | What it measures |
|---|---|
| Clinical | Something felt or lived, such as overall survival, a stroke, or freedom from pain |
| Surrogate | A stand in believed to track the clinical result, such as tumor shrinkage or a lab value |
| Patient reported | Symptoms, function and quality of life as the person describes them |
| Safety | Each recorded side effect, hospitalization or death from any cause |
Where do outcomes mislead?
A surrogate is the usual trap. A tumor can shrink, a marker can fall and a rhythm can correct without anyone living longer or feeling better, and treatments have reached use on a surrogate result and later proved to offer no benefit at all. Which survival measure is quoted matters too, since disease specific survival counts only deaths from the disease under study and can look strong while overall survival does not move. Composite outcomes bundle several events into one count and can be driven almost entirely by the least serious member of the bundle. And a result reported only as a relative change hides how common the event was to begin with, so a large sounding improvement may amount to very little in absolute terms.
Used in a sentence
The clinical trial measured survival as its primary outcome.
Good to know
A treatment can improve one outcome, such as tumor size, without improving another, such as overall survival, which is why researchers name the outcome a study is designed to measure before it begins.