An outcome measure is a specific parameter or event measured in a clinical trial to assess the effect of the intervention. It is essentially synonymous with the term ‘endpoint’. Outcome measures are critical as they provide the quantifiable basis for evaluating efficacy and safety.
Different types of outcome measures are distinguished. Clinical outcomes directly measure how a patient feels, functions, or survives (e.g., pain reduction, survival time). Surrogate endpoints are laboratory measurements or imaging results that serve as substitutes for a clinical endpoint (e.g., blood pressure reduction as a surrogate for preventing myocardial infarction). Patient-reported outcomes (PROs) capture the patient’s perspective directly (e.g., through quality of life questionnaires). The selection of appropriate outcome measures in the study protocol is a critical task that determines the relevance and validity of the trial.