a measure used in clinical trials or other research studies as a substitute for a direct clinical endpoint — the outcomes that truly matter to patients, such as survival, disease progression, symptom relief, or quality of life. Surrogate outcomes are typically laboratory tests, imaging results, or other objective/subjective measures that are thought to be reasonably associated with the true clinical endpoint, allowing researchers to estimate or predict the effect of an intervention more quickly.
Synonyms: Surrogate Measure
Example
In a diabetes medication trial, HbA1c (glycated hemoglobin) levels are used as a surrogate outcome for long-term complications such as kidney failure, neuropathy, or cardiovascular disease. Improvements in HbA1c predict a lower risk of these complications.